How Does Fat Loss Work?
There is so much controversy over the best way to lose weight and body fat. There are self-righteous religious arguments over low-carb diets (LCD), high-carb-low-fat diets (LCLF), paleo diets, vegan diets, and now we even have carnivore diets and intermittent fasting. There are questions such as, is a calorie really a calorie? What’s the best training to lose weight? Is strength training or cardiovascular training superior? Do you even need to work out to get lean? Then our TVs are riddled with muscle and bikini-clad models selling fat burners and diet drugs. Take this, and the fat melts off your stomach. Unless you have a degree in physiology, it can become confusing what you should do or even how to start losing weight and body fat. All these controversies have a lot to do with selling something to make money and because the topic has a lot of nuances, and science is always trying to figure these things out. My hope with this article is to make the issue a little more understandable so we can make good decisions on what to do.
Is It All About Energy Balance?
You’ve heard it before, calories in and calories out. Eat less and move more. But is a calorie really a calorie? My short answer is “yes,” but with some wiggle room. The laws of thermodynamics and energy conservation apply to human physiology and nutrition, so most weight loss will come from a negative energy balance (using more energy than you consume). But there is something referred to as nutrient partitioning, which I will get to later. For now, let’s discuss and understand energy itself.
Keeping this as childlike as possible, the human body has 4 primary energy production sources, but I will focus on three. First, muscles contract with ATP, so all your food or stored energy leads to ATP. The human body runs on sugar. We know this to be true because if it weren’t, then Type-1 diabetics wouldn’t die without synthetic insulin use. You have carbohydrates such as glucose (blood sugar), glycogen (sugar stored within the muscle), and dietary carbohydrate consumption. Then you have your fat stored in adipose tissue (cellular fat storage), also known as adipocyte, fatty acids circulating in the blood (triglycerides), a small number of intramuscular triglycerides, and dietary fat consumption. And finally, you have your amino acids from protein stored as muscle tissue itself and dietary amino acids from food.
The best way to describe how your body uses energy is to compare the human body to a big city. A major metropolitan city usually has people riding on the train, riding in cars and buses, and then walking. This is always happening all at once. But if fewer people use cars, more people will be on the train. If more people walk, fewer people are on the train and using cars. If each form of transportation is an energy system and the train is transporting our fatty acids out of the city, this is what most of us are concerned with as a goal. So, how this works depends primarily on our behavior and somewhat on our genetics. This article will explain how we get people off the street and on the train.
How is Bodyfat Mobilized and Burned for Energy?
As stated earlier, the human body is constantly using energy. It doesn’t matter if you are moving around or literally in a coma. You must consume dietary energy to stay alive. Even a chess player sitting in a chair uses a remarkable amount of blood glucose to power the brain. Most people aren’t exclusively concerned with weight loss but body fat loss. You can lose muscle tissue, bone tissue, water, fluids, and even a reduction if fecal matters and digestive residues result in weight loss. We all want to preserve lean tissue while losing as much body fat as possible. We need to liberate as many fatty acids from our adipose (fat tissue) into the bloodstream while limiting the number of carbohydrates and amino acids that enter the bloodstream to be burned as fuel.
To reduce the amount of stored body fat, fatty acids need to be mobilized from the fat cells into the blood first and then carried to the mitochondria (the cell’s engine) to be burned. Fatty acid mobilization is constantly occurring but more rapidly during energy deficits due to either a deficiency in consumed energy (eating) and/or increased energy utilization (physical activity). So, to summarize, fatty acid mobilization is highest in a fasted state, such as while you are sleeping and between meals and during physical activities such as exercise or labor.
The rate of fatty acid mobilization does not necessarily equal the rate of fatty acid burning, at all times. Fatty acids can be carried out of the cell and enter the bloodstream only to return to the fat cells called esterification. Obese people are known to have higher rates of fatty acid mobilization than lean people because they have a significant amount of fat available for fuel. But since they are overeating, their fatty acid storage rate (lipogenesis) surpasses their burn rate. This is also why obesity tends to give you abnormal blood triglyceride levels and blood vessel and artery wall inflammation. Any energy substrate can be converted to fatty acids and stored at any time. It’s hard to put a number on it, but in terms of losing body fat, in my practical experience, a calorie deficit covers 90% of the body fat reduction you can have. Having that 10% wiggle room is where all the nuances and controversies play out.
Fatty acid mobilization occurs through a few different means. The major player is catecholamine stimulation. Your body’s primary catecholamines are epinephrine and norepinephrine, also known as adrenaline and noradrenaline. Catecholamines raise heart rate and make energy available to fuel action. Catecholamines are raised during exercise, calorie deficit, or when chemicals are introduced that increase heart rate, such as stimulants. A secondary player is something called hormone-sensitive lipase (HSL). Sex hormones (testosterone, estrogen, and derivatives), growth hormone, cortisol, and thyroid hormones stimulate HSL to liberate fatty acids from the cells. Each modality leads mainly to stimulating beta-receptors, which signal beta-oxidation (fat burning) at the mitochondria. And then you have your alpha-receptors that, when active, suppress beta-oxidation. So, in an infantile equation, fatty acid liberation plus beta-oxidation stimulation plus alpha receptor suppression equals Abs!
Which Diet Works Best?
When calories are equated to a calorie deficit within the scientific literature, you don’t see a significant difference in fat loss. Some of these niche diets are relatively new and may require more research for me to change my mind on that statement. But in a practical sense, the diet that you can stick to over a long period would be the best diet for you as an individual, so I will break things down to discuss the benefits and trade-offs in the more popular ones.
Moderate-to-High-Carbohydrate-Low-Fat Diets (HCLF)
Man, that’s a lot of hyphens. This was the most widely prescribed for weight loss and physical performance for the longest time. But very rarely is this diet utilized in the general population. Instead, the general population with the financial means to do so and left up to their devices eats a high calorie, high to moderately high-fat, moderate-carbohydrate diet. Many of the foods people consider high-carb does, in fact, usually contain lots of fats and oils to manufacture and prepare.
Why has this diet been recommended for so long? I believe there were several reasons for this. Firstly, grains are grown in high volume, cheaply, on smaller parcels of land, and require less labor than animal care. Another is the idea that eating fat makes you fat. And finally, carbohydrates fuel performance, and the insulin released from carbohydrates is anti-catabolic or another way of preserving muscle mass.
Broadly speaking, these statements are primarily factual. Moderate carbohydrates at 4g/kg of body weight are recommended by the American College of Sports Medicine (ACSM) for strength athletes and between 7-12g/kg for endurance athletes. Carbohydrate consumption before and even during training to fuel performance is also recommended. We even have studies that show swishing sugary tasting drinks around your mouth and then spitting it out upregulates glucose utilization and increases performance measures, so even receptors within your oral cavity are at work. Blood glucose and muscle glycogen is the most readily utilized and quickest substrate for ATP production and muscle contraction. We have a whole body of studies showing that carbohydrate intake improves performance and lengthens the time to fatigue in aerobic and anaerobic training.
One area I want to tackle right away is the idea that carbohydrates are easily converted to glucose and then stored as body fat. Mechanistically this idea is flat out not accurate. The mechanism does exist and is called De novo Lipogenesis (DNL). But it is EXTREMELY difficult for ordinary people to activate this pathway. The muscles and liver can store between 12-16g/kg of carbs and even higher in people with high physical fitness. In addition, you must consume more than 100% of your total daily maintenance of calories of carbohydrates because even if you are at 90% of maintenance calories with carbs, the body will burn them for energy. There’s no excess to convert until you exceed the body’s entire daily maintenance calorie requirements from carbohydrates.
Studies have shown this quite clearly. In one study, the researchers depleted the subjects of muscle and liver glycogen. Then they fed the subjects between 700-900 g/d of carbs (a considerable amount). They ran some tests and found the body was still using fat for fuel, and the carbohydrates were being stored as muscle glycogen and not being converted to fatty acids. Another overlooked caveat is that eating more carbohydrates upregulates the storage capacity of carbohydrates in the muscles to some degree. The body adapts to a high-carbohydrate diet by getting better at storing more carbohydrates. The level at which this occurs depends somewhat on genetics and fitness levels which I will get to later. So, do carbohydrates themselves make you fat? The answer is no. But if you are eating at carbohydrate maintenance and have excess calories through fat, i.e., the typical Western Diet, that dietary fat will likely be stored. I will concede that it is possible to get fat on carbohydrates alone. If 500g/d is a maintenance number and you are eating 1000g/d, then DNL will occur. But most people aren’t living exclusively on fat-free carbs like Mountain Dew and gummy bears.
Carbohydrates also reduce protein breakdown for fuel (proteolysis) during rest and exercise. Have you ever heard, “you better eat, or you will lose your gains?” Besides its availability for fuel, carbohydrates also cause a rise in insulin which reduces muscle protein breakdown. Muscle anabolism is always based on the ratio between muscle protein synthesis and muscle protein breakdown. Mentioning insulin in a positive way is the most likely way to cause some people to throw rocks at my car windows. Somewhere along the line, insulin became the ultimate bad guy and the cause of all our obesity woes. It became a very polarizing topic even though even experts in the area like diabetes researchers still don’t fully understand everything insulin does. Remember that insulin is not a storage hormone but a regulatory hormone meaning its actions depend primarily on our behavior. I will go into depth on the relationship between insulin and fatty acids further in the article.
But insulin is also thought to be the most anabolic hormone the body produces. If you don’t believe me, ask any person with diabetes how much more difficult it is to add muscle mass? A spike in insulin combined with the presence of the amino acid Leucine is needed to activate the anabolic pathways to preserve, repair, and grow skeletal muscle tissue. Therefore, studies show that post-workout carbohydrates combined with protein consumption cause greater muscle protein synthesis than protein consumption alone. And finally, the literature does show that consumed dietary fat is easier for the body to store in the fat tissue because of the reduction of enzymatic processes in the body.
So, the question becomes, does any of this matter in a calorie deficit strictly related to body fat loss? The short answer is no. When calories are equated, there doesn’t seem to be a statistical difference in body fat loss compared to other diets, at least over the length of the studies, of which the majority are between 8 and 20 weeks. So, the main benefit of an HCLF diet is that you may be able to preserve exercise performance better. In addition, it might make it easier to maintain or even add muscle tissue during a calorie deficit.
Low-Carbohydrate and Ketogenic Diets
Although they are currently in vogue, low-carbohydrate diets are not new. A very old, out-of-print book called the Hollywood Diet described a low-carbohydrate diet combined with exogenous insulin use. This was back when being super skinny like Audrey Hepburn was what Hollywood was going for. So even at that time, people understood that if you drove your blood glucose low enough, the body would be forced to use more fat for fuel and crooked doctors were there to help. Some bodybuilders have been using LC diets for contest preparation since the 80s. But Dr. Atkins is who brought LC diets into the mainstream. And then, journalists such as Garry Taubes even began suggesting that the grain industry colluded with the government to trick everyone into believing that eating carbohydrates was healthy and the nation’s obesity crisis would be solved if everyone did away with all carbohydrates forever. I have no qualms about going on the record with my belief that Garry Taubes is willing to lie to keep his current financial endeavors going. But let’s look at what the research says and the pros and cons of low-carb diets.
There is some discrepancy on what constitutes LC and a ketogenic diet, for starters. Some researchers have classified anything under 200g of daily carbohydrates as LC and some as low as 30g daily. In practical terms, it probably depends on the individual’s body weight and general activity levels. For a 170-pound soccer player who runs 4-miles a day on the field, 200g would be low, but it might be considered moderate for a 100-pound sedentary female. There is also some confusion about Ketogenic diets, and they tend to be used interchangeably. Ketogenic diets are described that way due to the number of fatty acids converted to ketones when both carbohydrates and protein are significantly reduced. Ketogenic diets have been prescribed for a very long time in the treatment of epilepsy. So, medically speaking, in the proper ketogenic diet, protein is usually placed at the RDA minimum, which is lower than we want if we are concerned with body composition. Ketogenesis can occur in fasted, high-energy expenditure, or low-calorie states, but to be chronically ketogenic requires many restrictions.
Using an LC diet for fat loss is a very intuitive idea. Without carbohydrates, more fatty acids will be liberated to be used for fuel. Also, with lower carbohydrates, there will be less insulin. Insulin does suppress fatty acid liberation itself to a degree but does not completely shut it off. The release of insulin signals that fuel substrates are available for use and liberating body fat is not needed to the same degree. Also, there is an inverse relationship between insulin and growth hormone production. When insulin is low, more growth hormone is available to stimulate hormone-sensitive lipase, which liberates fatty acids. And finally, high-fat diets are shown to increase fatty acid mobilization and oxidation.
In plain speak, you become “fat adapted.” According to the research, this fat-adapted state only takes between a few days and three weeks. So, mechanistically, LC high-fat diets looks like the ultimate diet for losing body fat. But this idea, so far, has not produced superior results in the research. Although fatty acid oxidation is enhanced, fat storage is also enhanced. First, if you are consuming more dietary fat, you have more fat for oxidation through the diet and have more available for storage as well. And as stated earlier dietary fat is more easily stored as cellular fat than carbohydrates and protein. Also, low-carbohydrate and high-fat diets lead to insulin resistance. Researchers will use this nutritional protocol to induce insulin resistance to study diabetes. The effects are not permanent, so I am not implying that LC diets make you diabetic. That has not been proven to be true so far. Nutrition-induced diabetes is predominantly caused by obesity and overeating high-carbohydrate and high-saturated fat calories. But what even temporary insulin resistance does is it impairs muscle protein synthesis and leads to greater intermuscular triglyceride storage as opposed to carbohydrate storage which ultimately degrades high-intensity performance. And when carbohydrates are periodically introduced or reintroduced, the temporary insulin resistance will impede carbohydrate metabolism and cause elevated glucose blunting fatty acid elevation. This is a significant reason why low-carb dieters who return to previous diets may gain all their weight back and some extra for good measure.
So, when calories are equated, does a LC diet lead to more fat loss than a HC diet? At first, the research on LC diets was very promising. Short-term studies showed that LC diets showed more significant body weight loss than HC diets, which is why the popularity of LC diets took off. But this isn’t the end of the story. Bodyweight loss was not exclusively bodyfat. It was discovered that some of the weight loss was because of a reduction in muscle glycogen which carried cellular water with it. Glycogen is a hydrophilic compound, and each gram of glycogen is also attached to 3g of water. LC diets are often used in the last few weeks or days in weight-cutting sports such as combat and weightlifting to quickly reduce the fluid and scale weight of the athlete. However, when long-term studies were conducted for up to 6 months or even a year, there was no statistical difference in weight loss between LC and HC diets. Not only does this show that LC diets are not superior for long-term weight loss, but carbohydrates seem to be better for preserving lean body mass.
Before all the carb-phobic fellows start chasing me down with pitchforks and torches, let’s talk about the benefits of low-carb diets. The most significant advantage is that restricting an entire macronutrient also restricts the high-calorie, very palatable foods that make people fat. No more pizza, six-packs of beer, ice cream, and even things that are considered healthy like pasta and rice quickly go down our gullets and are easy to overeat. Next, protein and fat tend to suppress appetite better than carbohydrates. In general, fat and protein are very satiating because it takes longer to digest. A Ribeye steak may take 4-6 hours to digest entirely, but a cup of white rice in 1-2 hours. Also, the rise and fall of insulin you get from higher carb consumption can drive hunger. Within the general population in countries where food is plentiful curbing appetite is probably the most helpful approach to controlling obesity. And finally, LC diets encourage people to eat more protein. If you were previously on a low-protein diet, it enables you to raise your protein, and your body composition will thank you. Protein is not easily converted to fatty acids, and because it is difficult to digest, it requires more calories to fuel digestion. So, is a low-carbohydrate diet God’s gift to man? I don’t think. But it can be another tool to get people into a calorie deficit.
I will state my bias right off the top that I have a negative position on this diet. Intermittent fasting resembles every disordered eating pattern I have seen. And for the record, each of these diets I have done myself so that I would have some practical experience. Fasting is not new and has been part of many world religions for thousands of years. There are both spiritual and physical benefits to fasting but let’s stick to fat loss. The intermittent fasting craze started with the longevity crowd. There were two rodent studies where the researchers took half the rodents off the at-will pellet dispenser and limited them to 1 rodent chow meal in the evening but ensured each group received the same food. The rodents with limited eating time lived longer and had better health markers than the other group. We have lots of research to show that smaller critters who eat less live longer across all species, including humans, so no big surprise. The fitness industry latched onto the diet as a tool for fat loss, and it grew in popularity.
Many claims about the benefits started coming out of which. Some are accurate, and some are not. I will start with the one that is a huge misconception. It has been claimed that fasting preserves or even increases muscle growth because it leads to higher growth hormone production. Fasting indeed leads to growth hormone release, but the people making this claim have no expertise or understanding of what growth hormone does. The people with the highest growth hormone production outside of children and adolescents are people experiencing starvation. During fasting, growth hormone is released to stimulate fatty acid liberation, and, in that sense, it acts as a catabolic hormone. The most significant spike in GH comes at night when we are not eating but sleeping. The anabolic properties of growth hormone are due to its splicing in the liver into insulin-like growth factor (IGF-1) and mechano-growth factor (MGF). Though during fasting, IGF-1 is low, which means that the growth hormone is not stimulating muscle anabolism but fat catabolism. When people experiencing famine are tested, they have sky-high growth hormone and very little IGF-1. To summarize, growth hormone is systemic and not a selective hormone, and its behavior is dependent on our behavior. I will revisit this idea later.
Since intermittent fasting is relatively new, only a small body of literature compares it to more frequent eating. The research hasn’t shown anything surprising or remarkable in the small body of studies. When calories are equated between groups, there was no statistically significant difference in weight loss between intermittent fasting and more frequent meal groups. But the intermittent fasting groups had less lean body mass than the regular meal groups. So, intermittent fasting leads to weight loss but may result in less lean mass and more body fat. A theme is developing where 90% of a calorie is still a calorie.
This reduction in lean mass preservation is most likely due to decreased performance or maybe even physical activity. And an almost guaranteed higher rate of muscle protein breakdown to be used for fuel. And more likely than not, due to both micronutrient and macronutrient deficiencies. Although we don’t have many studies on intermittent fasting, we have a body of literature on performance studies on fasting athletes. Studies show that eating closer to exercise, especially carbohydrates, improves performance. We have studies showing that consuming energy during exercise improves performance. And we have a lot of studies that show that Muslim athletes have a reduction in performance during fasting for Ramadan. Micronutrient deficiencies are likely to occur because there is only so much food you can fit into a small window. If 4 to 6 servings of fruits and vegetables are required to prevent micronutrient deficiencies, can you practically get all your servings at once and everything else you need to eat? People also don’t realize that specific vitamins and minerals compete for the same metabolic pathways. For example, calcium binds to magnesium, rendering magnesium unusable to the body. This is prevented through smaller and more frequent doses of vitamins and minerals. Therefore, even a multivitamin does not work as well as getting these nutrients in smaller quantities in real food. The next issue with intermittent fasting is getting the necessary protein to preserve muscle mass. Unlike other macronutrients, protein accumulation, also known as nitrogen balance, depends on frequent intake. 1.6g/kg/d is shown to maximize muscle protein synthesis. So, a 100kg person would need 160g per day. That is a lot of protein to eat in a short window and if you are a vegan, then forget about it. Maybe you are ok with eating less protein, but there is still a problem. The laboratory research shows that the cutoff for usable protein through muscle retention is approximately 40g at one time. Therefore, anything above that will result in proteolysis, converting those amino acids to glucose for fuel.
Now that I have thrown all my stones, let’s talk about the benefits of intermittent fasting. By restricting eating to a specific window of time, you are most likely preventing the ability to consume too many calories. But is it possible to still overeat? The answer is yes. Sumo wrestlers have historically consumed most of their calories in the evening when all the days training is done, mainly because their status earns them free food at many restaurants in Japan. Therefore, they do a lot of spiritual fasting during the day before and between training. But overall, it is a practical tool to get into a calorie deficit. Fasting also shows people that if you go without eating for a certain period, you aren’t starving to death and may help people overcome the psychological side of hunger. Some proponents also claim it leads to better mental clarity and concentration. This is not a topic I have dove into but reducing energy swings may lead to this effect. This may be part of the spiritual benefits of fasting.
Nutrient Partitioning, Exercise, and How to Get a Big P!
So far, we have established that the main driver of body fat loss is a calorie deficit. People may disagree with me on the best way to do that, but most people outside of a few snake oil salesmen would agree that calories matter.
Some people have taken the idea that a calorie is always a calorie too far and this trend popped up in fitness a while back called “if it fits your macros” IIFYM for short. A couple of the critical promoters have been Layne Norten and Alan Aragon. Both are sharp guys with higher education and have recently eased up on this idea, but it helps set up my next theme. IIFYM meant that if you got the ideal number of calories, protein, fat, and carbohydrates to fit your body composition, it didn’t matter where those calories came. So, you have proponents sharing their meals on social media that include a healthy chicken breast, a couple of stalks of broccoli, three peanut butter cups for their fat and carb, and then bragging that they could eat candy and still have abs. Are they liars? No, but I still believe they could get better long-term results with a different approach. So, let’s follow the rabbit down the hole.
We all know people who seem to shove copious amounts of food in their faces with reckless abandon and never have a change in body weight or composition. And then we also know people that eat a potato chip before bed and wake up fatter. Scientists and obesity researchers have spent a long time figuring out why this occurs. There have been some tremendous overfeeding studies where people eat in huge calorie surpluses, and some people gain a little weight, some a lot of weight, some none or an insignificant amount, and some outliers lose weight. Other studies use diets and exercise where some lose a lot, some a little, and some a negligible amount. So, what is going on? Is it glandular, thyroid, or does God want me to be fat?
We have found that people can be very good at subconsciously maintaining their body weight regardless of if they are big or small. Your skinny friend who eats whatever they want most likely moves more without knowing it. And your large friend who starts restricting calories will also begin moving less without knowing it. Research has labeled this phenomenon as non-exercise-related activity (NEET). When someone has a genetic predisposition for staying small, the more they eat, the more they will get up, move around, and even fidget more in their chair. And the overweight person who goes on a diet may just sit around more without even knowing it. This phenomenon has played out with exercise as well. Some people are dedicated to the gym, but they sit around more than if they hadn’t done their workout. Therefore, activity and step tracking has become a helpful tool. Not only to give people a goal to increase their NEET. But also, you can find out what your steps were before you started to diet and exercise and make sure they wouldn’t go down. Changes in NEET can also change the further you get into a diet. The closer you get to your goal, the more your body will fight you on continued weight loss, and the overall lethargy can set in.
Is this the whole story explaining why some people quickly lose fat and others don’t? No, another facet to this is nutrient partitioning. Nutrient partitioning refers to essentially the distribution of where our energy is stored. We probably know someone who has hit the genetic lottery. The protein they eat builds their muscles, and the carbs they eat are stored as muscle glycogen, so the fat is left to be burned for energy. These are the people who could potentially become world-class athletes, fitness models, basically the Arnold Schwarzeneggers of the world. Our nutrient partitioning ability is determined by our general fitness, sex hormonal levels, insulin sensitivity, and androgen and cellular receptor affinities. Researchers have labeled this as your P-Value to put a mathematical number on this ability. I’m referring to that 10% of a calorie not being a calorie. If we raise our P-Value, we can make the body more efficient at storing protein and carbohydrates and mobilizing fatty acids.
Ok, coach, how do I get a big P? Well, this is what testosterone, estrogen, and steroids do. Therefore, you may have been able to eat whatever you wanted in high school because of puberty. But if this, isn’t you, then the first place I’m going to go with this is what everyone loves to hate, cardiovascular training. In my world, most people do what they can to avoid it. I constantly get questions about whether it is possible to get lean without cardio. The answer is yes. It requires no work to eat 500 fewer calories, and to use 500 calories on the treadmill is a lot of work. But I’m going in a different direction with this.
Prolonged or high-intensity cardiovascular training mobilizes fatty acids from adipose tissue to be burned. That alone is a benefit, but also cardio training improves mitochondrial function and number, which has shown people with good aerobic fitness metabolize more fatty acids both during exercise and at rest. As a result, you get better at using fat for fuel and preserving carbohydrate retention. There is also an upregulation of enzymes involved in the metabolism of polyunsaturated fatty acids. To put it plainly, it doesn’t just burn fat but changes the composition of your stored fat. I could get into how this works, but without confusing everyone, it changes your body fat composition to reduce inflammation and improve insulin sensitivity. Having better insulin sensitivity gives you better metabolism and more favorable energy storage. As a result, you will store more carbohydrates in the muscle, more protein will be metabolized to repair and keep as muscle, and more fatty acids will be mobilized for energy. Another phenomenon that happens through cardiovascular training has been labeled as “beiging.”, You have a white-colored bodyfat and a small amount of beige bodyfat. The beige bodyfat is interesting because it generates heat to stimulate white fat mobilization to be burned as energy. So, it promotes weight loss and causes resistance to obesity. Obese people have been found to have low levels of beige fat. But we now know that cardiovascular training changes our bodyfat composition to a higher number of beige adipocytes. And finally, aerobic endurance training also upregulates the amount of glycogen stored in the liver and muscles. So, people with a higher level of fitness flat out store more sugar and less fat. So, yes, you don’t need to do cardio to lose body fat, but in the long-term, it will aid in your fat loss journey and help you resist adding body fat back on in the future, such as when you are trying to gain bodyweight. Especially if you aren’t using drugs to augment your nutrient partitioning
High-Intensity Cardiovascular Training (HIIT) vs. Long Steady-State Cardiovascular Training (LISS)
Researchers have been trying to figure out if HIIT or LISS is better for health and weight loss for a long time. It is a complex topic, so I will summarize things very straightforwardly. In terms of health, most of the studies show no differences in health benefits such as blood pressure modulation between the two modalities. Each has its different benefits, but it is not hard to figure out why there is not much difference in the studies. If you do long-duration cardio at a heart rate (HR) of 130 or do a short duration of cardio cycling between bouts of an HR of 160 or above and 110 during rest, the averages HRs between the two modalities turn out to be similar. It has also been shown to be approximately the same for fat loss. The body is very good at preserving its available energy. So, if you do long-duration cardio in the “fat-burning zone” of 120-135 HR, you will use more fat during exercise. But at rest, the body will use other fuel sources such as glucose and glycogen. With HIIT, you will use more glucose and glycogen for fuel, but afterward, your body will use more fatty acids for energy, called post-exercise oxygen consumption. So, it becomes a wash. Which modality you choose should be based on your goal and time availability.
If you are doing cardio in the morning and strength training in the evening, I will choose LISS because you will preserve more of your carbohydrate stores to fuel your strength training. If you are doing your cardio afterward, then either modality is acceptable. Then, on separate days again, either modality is acceptable. You must be concerned about using HIIT because it creates more systemic fatigue and muscle damage. Therefore, I would be mindful of your training load and limit HIIT sessions to twice per week. But if you have significant time restraints and 20 minutes of HIIT fits in your schedule, I will always concede that you should pick the form of cardio that you will do consistently.
Moderate-to-High Intensity Long Duration Cardio
This type of training is mainly reserved for competitive endurance athletes. It is the most energy-intensive exercise, so dietary recommendations are considerably higher for people who engage in it. This form of training utilizes a large combination of both fatty acid oxidation and glucose/glycogen burning. This exercise also tends to use more proteolysis and muscle breakdown to fuel training.
It will work remarkably well to increase calorie expenditure and improve fitness but with the most significant expense of systemic fatigue and possible muscle protein loss. People who engage in this type of training will find it challenging to preserve and put on muscle mass. Therefore, you don’t see any hyper-muscular soccer players and why marathon runners and cyclists are rail thin. It would be a foolish goal for endurance athletes to have large bodyweights. Still, even if they spend significant time in the weight room, which many do, they will find adding substantial muscle mass a fundamental limitation, especially in their legs. If you are at a considerable bodyweight already, this form of training can be contraindicated because of the repetitive pounding that occurs and creates significant joint and muscle damage. Even small athletes find it difficult to stave off overuse injuries from this training when the volume is high.
Although I am a strength coach by trade, I will keep this section short and to the point. Strength training potentially raises all your hormone levels, which will increase your P-Value. There is a correlation between the amount of muscle you have and lower blood glucose levels. Strength training activates Glut-4 translocation and allows carbs to be absorbed without insulin. Recovery from strength training requires aerobic metabolism and increases fatty acid utilization for hours after completion. All of which improve your insulin sensitivity, nutrient partitioning, and fat loss. Strength training is fantastic.
Nutrient Timing and Choices
This is an area of debate as to whether timing matters. It was believed that you had this short anabolic window where you wanted to get your most essential nutrients immediately following training. With better measurement techniques, we now know that the anabolic window is much longer, up to several hours and some researchers hypothesize it may be an entire day. I believe that nutrient timing can make a difference by a few percentage points when trying to get lean. But overall, I like to keep things simple because, again, most progress will be made with energy balance. Try to think about things in 3-to-4-hour blocks when it comes to timing. Your nutrition should be focused on what you will be doing or what you just did. So, to keep things simple most of your carbohydrate and lower fat meals should be concentrated near and directly after your workouts and be tapered down closer to bed. You don’t need dietary fat to fuel your training, and unless you run on a treadmill in your sleep, there aren’t many purposes for eating carbohydrates late in the evening. Also, the insulin release will impair growth hormone secretion in your sleep to some degree. The exception is if you are on a low-carb diet or training right before bed. When on a low-carb diet, consuming some medium-chain triglycerides (MCTs) may be helpful within a couple of hours before your workout to fuel your performance. MCTs are broken down by the liver reasonably quickly and made available for energy more similarly to carbohydrates. If you are training right before bed, between 30 and 60g of carbohydrates is an excellent idea to replete some of your glycogen stores before sleep. There shouldn’t be any fat storage in that environment during your sleep. And the most forgiving time for bigger meals can be directly after your training because the carbs and protein will be used to replenish your energy and not your body fat. Our studies show that fatty acids continue to be released and burned after training, even in the presence of food.
What about Severe Obesity
For the record dealing with clinical obesity is a little outside of my wheelhouse. But I will cover some general considerations. Obesity is defined as someone who has a body mass index (BMI) of 30 and above. The exception is a hyper muscular person, but those people are, in fact, rare. Having obesity, especially over a long period, is likely to come with some health conditions that impact nutrient partitioning and make it harder to lose weight. That is why the first thing that should be done is get some medical testing. Your doctor will probably want to check blood pressure, cholesterol, and blood sugar. It may be a good idea to check your thyroid as well. Although many overweight individuals like to assume it’s a thyroid problem and not their behavior, thyroid issues, especially in men, are rare. But hypothyroidism will impact obesity, so it’s good to rule that out as a problem. The primary test I would be concerned with is blood sugar. If your blood sugar is high, the next step would be to check A1C or both simultaneously.
Elevation in blood sugar can be momentary or related to recent behavior, but AIC can indicate that you have insulin resistance. If you have insulin resistance, you will have much more difficulty losing body fat and building muscle. If you look at the body shape of someone who has had diabetes for a long time, they usually have large protruding stomachs and skinny arms and legs. This is because insulin resistance causes fat buildup around the waist and muscle loss. If you have insulin resistance, you can do a couple of things. No matter what, losing weight will help improve this condition. You might find that losing weight alone causes insulin resistance to disappear, but that is not guaranteed. Or your doctor might choose to use medications to help control your blood sugar and help you lose weight. A common one is Metformin which prevents the release of glucose into the blood by the liver. Metformin alone is shown to reduce body weight in people with insulin resistance. Another medication is GLP-1 agonists. These drugs not only lower your blood sugar but also suppress appetite, so they are an effective medication for the combination of obesity and insulin resistance. And finally, if you have high blood pressure and insulin resistance, there is a medication called telmisartan that lowers BP and controls glucose and has been shown to cause weight loss in people with insulin resistance.
In terms of diet, in this case, a low-carb or reduced carbohydrate diet would be warranted, at least temporarily. Since you have an impairment of carbohydrate metabolism lowering the carbohydrates may be the only way to reduce blood glucose enough to maximize body fat utilization. This is not a guarantee, though. Once the weight has been lost, you will still have insulin resistance because you have not been consuming carbohydrates. To return to a regular diet, it is best to introduce carbohydrates in one meal at a time slowly. It should only take a few weeks, and then get your A1C rechecked.
The other thing to consider with obesity is the number of calories needed. To put it plainly, if you are obese, you only need protein, a small amount of dietary fat, liquids, and micronutrients to survive. You have plenty of energy stored where you won’t starve to death. For consecutive days without food, the Guinness World Record is 382, but the individual started at 456 pounds. It is still a good idea to start with a slight calorie deficit. First, if you are in this state, you probably have hunger and appetite issues. A severe calorie restriction may be overwhelming in terms of hunger and stress. You also must be concerned with the rate of fat loss on your skin. The skin is an organ and can get larger and shrink. The slower you lose weight, the less chance of loose skin. If you are severely overweight, this may be a certainty and require skin reduction surgery to correct the problem.
But I know in emergency medical situations, doctors who work with severe obesity will put people on diets of only 1600 calories. This seems to be the minimum number of calories needed to prevent micro and macronutrient deficiencies. But I would also worry about hormonal downregulation with such a large calorie deficit. As progress slows, I would start at a higher calorie marker and taper things down.
Regarding physical activity, you may have limitations because of the orthopedic stress your body has undergone due to the significant body weight. In this case, it may not be a good idea to jump right into high-intensity training. Simple walking, low-impact cardio like the elliptical machine, and swimming will provide adequate stimulus to start the fat loss journey. You do not need high-intensity training to get the heart rate elevated at a significant bodyweight because you are essentially carrying a weight vest around with you everywhere you go. Raising your NEET will pay off big time. Establishing a step count and going from 5000 steps and adding a thousand steps per week until you get 15-20,000 will improve fat loss significantly. Other strategies may include getting up from your desk every 15 minutes to stretch your arms and legs. Taking a walk to the water cooler every 45 minutes or parking as far as possible from your office, there are endless possibilities to increase your activity throughout the day. I suggest weight training and utilizing the many machines available to limit joint stress. If you have been large your entire life, you do have a great deal of lean mass. You have been carrying around that weight vest which added muscle mass, especially in the legs. It’s a good idea to preserve that mass to make you look better, keep your metabolism high and prevent loose skin. The other benefits were stated earlier.
Going from Lean to Super Lean
I will state that outside of training for high-level sports, only a small number of people can genetically stay in single-digit body fats without complications, so be aware of that if it’s your goal. But the closer you get to single-digit body fat, the more difficult it becomes for a few reasons. First, you get plain lethargic, hungry, and overtrained. To get very low body fat, it is likely that calories have tapered down low, exercise such as cardio may have increased, and your overall ability to recover has been depleted. Therefore, to go further requires a fair bit of mental fortitude. When my athletes cut weight for an event, I refer to the ones that cut a substantial amount as hangry. In general, your irritability might go up.
There also can be a downregulation in hormone levels to keep you from losing more body weight. You see, nature doesn’t care about visible abs. Your systems are designed to recognize possible famine. Once you have been dieting long enough, there is an expected reduction in testosterone and thyroid hormone. We have good data to show this in both drug-free physique competitors and elite endurance athletes. Drug-using athletes start to introduce replacements for these hormones when dysregulation occurs. This may have a detrimental effect on your lifestyle. The joke about drug-free bodybuilders near an event is that even if they could get it up, they don’t care because they have no libido anyway. And finally, the fat loss gets hard when significantly lean because we all have stubborn body fat stores. These fat cells have less blood flow and fewer receptors to activate their release. These cells again are there for survival during a famine. Think of them as the emergency oil reserve. So, the limiting factor to fat loss because fat mobilization.
We can mitigate some of these issues by using diet breaks. In the same way, your training should have a periodization. Your nutrition should as well. A diet break is not where you go back to your old way of eating but to bring your calories back up to maintenance levels. You may put a little water weight on in the process but not fat. This allows your hormone levels to come back up and stabilize, and it may create a new setpoint for your body weight. Setpoint theory establishes that if you are at a bodyweight for long enough, your systems recognize this as usual or ideal. Then when you try to lower or raise your body weight, there are mechanisms to work against getting too far from the set point. The people who subconsciously move more when they eat more are a good example. So, if we take 5 to 8 weeks off a diet and eat at maintenance, we may learn to function at lower body weight.
As far as stubborn fat, this is when the rate-limiting factor is fatty acid mobilization itself. You may try to do more exercise and eat less, but instead of losing body fat, you could experience muscle loss. This is a harsh reality with weight class sports and drug-free physique competitors. To get that last pound of fat off, you may be sacrificing a couple of pounds of muscle. The only way I’m familiar with reducing stubborn fat outside of just more dieting and exercise is through pharmacology such as fat burners and possibly fasted cardio.
Do Fat Burners Work?
Yes, several fat-burning drugs do what they do. But the question is not do they work but are they appropriate for you. First, let’s discuss how they work. Most of them are based on beta-anergic stimulation. Meaning they increase epinephrine, which stimulates the mobilization of fatty acids and increases heart rate, increasing the burning of energy. A lot of the data shows that over-the-counter fat burners raise metabolism by 8 to 10% for a couple of hours. A couple of side benefits are they also upregulate neural activity helping with focus and exercise performance and are descent appetite suppressants. So, on a diet, these can be very positive. In over-the-counter fat burners, the main ingredient is caffeine. Although there are usually more ingredients for marketing purposes, caffeine is one of the most widely studied drugs in history, and we know that it works. Caffeine increases heart rate and increases intracellular cyclic adenosine monophosphate (cAMP), which helps liberate fatty acids into the bloodstream. So, caffeine encourages fatty acid mobilization with or without an increase in heart rate. A standard dose for the performance effects of caffeine is between 2 and 6mg per kilogram. The adequate amount depends substantially on the individual’s tolerance for the compound.
So, here is the bad news. First, stimulant-type fat burners tend to be contraindicated for people who need to lose weight. Using stimulants should be predicated on whether you have healthy blood pressure and vascular health. These drugs would increase HR and BP substantially and even higher during a workout and put you at risk for left ventricular hypertrophy, vascular damage, and even heart attack or stroke if you were on your way. You also must ask yourself if you are at a stage of weight loss that would warrant taking drugs. If you have 50 pounds of fat to lose, fatty acid mobilization is not a rate-limiting factor in your weight loss. When you are in this condition and on a diet, you have no problem losing body fat without any bells and whistles. Also, you don’t want to run these drugs for more than a few weeks. So, if it will take you 30 weeks or even a few years, it is best to save these tools when you need them, like the last 5 pounds. I will go over a few more of them besides caffeine.
Yohimbe comes from the bark of a tree and can be synthesized into a synthetic version called yohimbine HCL. It has been used as an aphrodisiac for a very long time. It was later discovered that it increases nitric oxide and allows better blood flow strengthening erections. But remember earlier in the article when I talked about beta-receptors vs. alpha-receptors. Beta-receptors encourage fat mobilization, and alpha-receptors suppress. Yohimbine is an alpha-receptor antagonist. This means you will get more fatty acid mobilization and longer when the beta-receptors are stimulated. A standard protocol is to take 20mg along with caffeine before fasted cardio. Yohimbine is known for causing anxiety and possibly an irregular heartbeat because it prolongs the beta-anergic response. Many people have trouble tolerating these side effects, but it does nominally work. If you choose to use Yohimbe, I will opt to use the Yohimbine HCL product because it is a standardized dose. If you use the Yohimbe herb itself, the active ingredient may be underdosed or, worse yet, overdosed. I and I would start at a low dose of 5mg before your cardio to see how you tolerate the product and titrate the amount up to a maximal of 20mg over a few weeks.
Several asthma medications have been used off-label for fat loss for several decades now. Asthma medication vasodilates the bronchial tubes and agonizes the beta-receptors. The most notable one that is bought off the black market is clenbuterol. Clenbuterol is still prescribed in some studies countries, but many now use a cousin compound called albuterol. Clenbuterol is still used with livestock because it has anabolic properties as well. In studies comparing the fat-burning effect of albuterol vs. caffeine, albuterol was 10% more effective than caffeine. Clenbuterol is approximately ten times more powerful than albuterol, making it very effective. Clenbuterol is so effective because its half-life is 36-48 hours, which means you have a chronically increased metabolic rate compared to caffeine, which is about 4 hours. Although the length of action makes it very effective, having a chronically elevated heart rate and blood pressure puts a lot of stress on the heart and vascular system, which could lead to an enlargement of the heart, specifically the left ventricle.
Ephedrine is another asthma medication like clenbuterol and albuterol. The advantage of ephedra is that it is used in pill form before activities that are more likely to cause an asthma attack, such as physical activity. An inhaler is used only as a possible asthma attack occurs. Because of its ability to encourage fatty acid oxidation, it started to appear in weight loss supplements and is commonly called the ECA stack. If you read the drug interaction warning for Ephedrine, they include not using caffeine and aspirin at the same time because they increase the potency of Ephedrine. But if you were not interested in using Ephedrine for asthma but fat burning, you may be interested in combining the three compounds. When combined with caffeine, the effectiveness of Ephedrine becomes a 1+1=3 equation for fat loss. Aspirin acts as a methyl donor, which prolongs the action of both drugs and allows it to have similar effects to clenbuterol. The ECA stack was restricted from the supplement market in the United States after a few high-profile deaths occurred in college football, and it was discovered the players were using it before practices. Also, Ephedrine can be used as a critical ingredient in the manufacture of methamphetamine. Although it is restricted from supplement sales, it is still available over the counter in asthma medications at pharmacies, but there is a limit to how much can be purchased at one time. It’s another drug to take your blood pressure and vascular health into account before using.
Morning fasted cardio has been used forever by athletes making a weight class or physique athletes and models ready for an event or photoshoot. It is intuitive to train because the overnight fast lowers blood sugar and starts the fatty acid mobilization process. And then, getting up and exercising before eating will further enhance fatty acid mobilization. This has been studied extensively in endurance athletes and is used to help endurance athletes become fat adapted. So first, they would train fasted with low-intensity long-duration work sparing their muscle glycogen. And then, in the afternoon or evening, they would do their high-intensity work.
Good research shows this occurs, but the analysis comparing fasted and unfasted cardio with recreational exercises are sparse. I am aware of two studies that show no significant difference between fasted and unfasted cardio on weight loss. The reason for this could be two reasons. First, if you use more fatty acids during exercise, there is a shift in energy to carbohydrates after training, so the calorie expenditure becomes a wash. The caveat of these studies was that the subjects weren’t significantly lean to start, and fatty acid mobilization may not have been their limiting factor in weight loss. So, it is still unknown if fasted morning cardio offers a significant advantage to individuals that are already lean beyond anecdotal evidence. At the very least, both methods are effective for weight loss, and fasted cardio doesn’t pose any risk unless you are prone to hypoglycemia.
Frequently asked Questions
Q: Which alcoholic beverages should I drink so that I don’t impede my progress?
A: Each gram of alcohol contains seven calories, and a standard drink contains 15g of alcohol. Alcohol drinks such as wine, beer, and mixed drinks do have quite a bit of sugar. But the calories alone aren’t the big culprit in how people get fat on alcohol. The body recognizes alcohol as a poison and makes its metabolism the number one energy source. So, while you are under the influence, most of the other forms of energy you have consumed are more likely to be converted and stored as fat. Therefore, it is wise to moderate alcohol usage during a diet and lower the calorie count on the days you know you will partake. To reduce the calories of the alcoholic drinks, you may choose to use clear alcohol drinks and mix them with diet soda instead of beer and wine.
Q: Should I do a juice fast to kickstart my diet?
A: You can quickly lose substantial weight on a 2 to 7-day fasting style diet, but it may be more trouble than it’s worth. Many of the weight you lose will be water weight and bowel irrigation. You will lose body fat, but you don’t require a substantial calorie restriction to make significant progress at the start of the diet anyway. Going from not eating to adding calories back in will result in some weight regain, which may be discouraging. I think there are less painful ways to start a diet. Juice fasts and the like seem to cater to impatient people without a long-term plan.
Q: Can’t I just eat clean instead of counting my calories?
A: Yes, but clean is a subjective term. In most peoples’ minds, clean means eliminating junk food like baked goods, fast food, and pizza. In other peoples’ minds, clean means no sugar or carbohydrates, but bacon is ok because it isn’t a carb. The elimination of junky palatable foods tends to reduce calories but isn’t guaranteed that progress will continue without knowing your average calorie expenditure compared to your calorie consumption. Tracking for even a short period allows you to learn to read food labels, understand how much to eat, and establish new habits such as moderation.
Q: Can I have a cheat meal or cheat day?
A: Yes, but keep in mind that progress comes from averages over time, so you must be careful not to let your cheat meal negate your progress throughout the week. If you are in a daily 500 calorie deficit and eat a 2,000-calorie cheat meal, you have effectively denied four days of dieting. Cheat meals should be planned around social events, and it is intelligent to reduce the calories of your other meals that day. An entire cheat day probably asks for frustration and will start to resemble disordered eating patterns.
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