How many people do you know who exercise to burn/lose fat?
The whole mentality is, if you jog for 60 min, you burn 500 calories, which will help you to stay lean.
Or, I can eat food, but I have to exercise afterward. Or even worse, if I exercise, I can have these foods.
I want to tell you that this whole concept of exercising for fat loss is backward.
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Here is what the article will be about:
- Quick recap on energy expenditure
- Which kind of exercise promotes fat loss and how
- Compensatory behavior induced by exercise
- Why exercise for fat loss doesn’t work
- Fat free mass, cardio, weight training and hunger
Quick recap on energy expenditure.
Resting metabolic rate accounts for at least 50% of our calories expended. Things like thyroid and androgens can increase our resting metabolic rate.
The thermic effect of food is only about 5-15% of our total calorie expenditure.
Finally, activity energy expenditure can account for up to roughly 2000 calories extra calories. A sedentary couch potato will burn around 200-300 calories per day, whereas someone that works outdoors can burn up to 2000 or even more on a daily basis. Burning calories by activity other than exercise are also called NEAT; non-exercise activity thermogenesis. Exercise activity thermogenesis is called EAT.
If you jog for about 60min each day, you’ll burn between 300-500 calories extra.
If you’re active (not from exercise) on a daily basis, because you’re full of energy, your NEAT can be around 1000-1400 calories.
- Check out last week’s article to learn more about NEAT.
So clearly, doing exercise to burn fat is an inferior way of going about it.
Now I understand that if you’re taped to a chair all day and held there by gunpoint not to move, then you might have built up energy to go and exercise afterward.
But don’t think just because you exercise, you’ll lose fat. Check out this study for example.
They compared two groups (obese men), one group did low-intensity training, 40% VO2, and the other did a high-ish intensity, 70% VO2 max, and after 12 weeks, body fat remained basically the same. Showing that exercise for fat loss was basically very ineffective.
Let me show you the science of fat loss from exercise.
The exercise for fat loss theory is broken
The study above showed that exercise didn’t result in fat loss, which is impossible, since increasing calories out should reduce fat mass right? Well, unless they increased calories in at the same time. More on that in a bit.
The majority of studies looking at exercise and fat loss find that it does promote fat loss if all other variables are held relatively constant.
Exercise training decreases abdominal fat in an intensity-dependent manner, with HIIT (high-intensity interval training) or HIST (high-intensity sprint training) being the most effective.
This is odd (or so the researchers thought) since there is a decrease in fatty acid oxidation during HIIT despite an increase in lipolysis. Also, 24-h fatty acid oxidation during and after exercise is unchanged and does not provide support to the causality between fat burning and fat loss (R).
HIIT is better at promoting fat loss, despite reducing fat oxidation, compared to low-intensity exercise, which does increase fat oxidation.
The reason why HIIT is superior for abdominal fat loss is because exercise increases plasma epinephrine levels at high intensities. Epinephrine stimulates lipolysis and inhibits the esterification of triglycerides via adrenergic receptors of adipocytes, leading to the release of free fatty acid from adipose tissue into circulation.
Long-term adrenergic stimulation (e.g. clenbuterol) has been shown to decrease fat mass and increase muscle mass without changes in food intake and body temperature. Abdominal adipocytes show much higher lipolytic response to epinephrine than gluteal adipocytes, which may partly explain the commonly observed abdominal fat loss response to high-intensity exercise training (R).
How HIIT results in better fat loss, despite not burning fat
This research paper speculates that’s it’s likely that the decreased abdominal fat accumulation after HIIT is associated with increased muscle regeneration attracting more postprandial carbon and nitrogen to exercised muscle tissue vs the abdominal adipose tissues (R).
They say that because of what happens to lipoprotein lipase (LPL). LPL attached on the surface of endothelial cells in capillary lumen determines relative partition of circulating triglycerides to muscle and adipose tissues after meals (R).
This ratio is substantially influenced by exercise training, in which trained individuals have a relatively higher (∼8 times) muscle-to-adipose tissue LPL ratio compared to their untrained state (R). Meaning, fat goes to the muscle for fuel and regeneration, instead of adipose tissue for storage.
- Fat burning does not equal fat loss
- Myth: fasted cardio is better for fat loss. Busted.
- The dope on blocking fatty acid oxidation
Compensatory behaviour induced by exercise
This is probably the biggest reason why exercise for fat loss doesn’t work.
When people are “forced” to exercise, either because they feel guilty due to the food they ate, the excess fat they have, because they think they should or whatever the case may be, they compensate in other areas of their lives.
Behavioral compensation can attenuate or even reverse the energy deficit generated by exercise and is estimated to result in 55% to 64% less weight loss than predicted during exercise interventions (R). In general, instructing people to exercise more to lose fat typically fails to produce expected weight loss (R). It’s highly ineffective.
The two areas where they compensate is via:
- Increasing food intake – subconsciously or as a reward
- Reducing NEAT – because they’re tired from the exercise they did
This study shows that, consistent with the concept that “more is not always better,” exercising two days a week was capable of increasing NEAT but, paradoxically, an intense three days weekly schedule was followed by a substantial decrement in NEAT (R). The more you exercise, you more likely you are to be tired and actually reduce your NEAT for the rest of the day or even for the next day.
Here is a neat study that looked at just that. Compensatory behavior induced by exercise.
They took 48 overweight and obese individuals and had them do 30min of treadmill walking.
What they found was that 63% compensated for the energy expended during exercise by increasing their food intake or decreasing their NEAT (R).
Importantly, this average response to exercise had considerable individual variability. Of the 63% that behaviorally compensated for the energy expended during exercise, 73% reported compensatory increases in food intake following exercise. Of that 73%, half increased their energy intake following exercise by an average of 796 kcals (R). Do you see how crazy that is? Let’s say 30min of exercise burns 200-300 calories. If you add in almost 800 calories, you’re in a 400-500 calorie surplus. Totally the opposite of what they wanted. From the results of this study, someone can make the case that exercise can make some people fat.
Furthermore, of the 73% that compensated, 43% demonstrated compensatory reductions in NEAT. Although the majority showed compensatory changes in either energy intake or energy expenditure following exercise, only 17% both increased energy intake and decreased energy expenditure (R).
So keep in mind here that I’m not saying that everyone will compensate, but a relatively large portion will/might. Of the portion that compensates, most will increase food intake, a little less will become more sedentary and only a small group will do both.
Think of it this way, when you fast, you have no energy to do anything and you can only think of food. Going into a deficit via diet or exercise is a milder version of fasting. Your body senses a deficiency and wants to avoid that.
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Why exercise for fat loss doesn’t work
With over 66% considered overweight or obese with a body mass index (BMI) of 25 kg/m2 or greater, the amount of weight loss from exercise training is often disappointingly less than expected with greater amounts of exercise not always promoting greater weight loss.
This is a “strange” finding, since burning energy via exercise seems like such an attractive modality. Depending on an individual’s aerobic fitness, exercise intensities can be maintained for prolonged periods at two- to 16-fold above resting rates of energy expenditure. As such, 250 to 2500 kcal can be expended during a single exercise session resulting in an acute energy deficit that can be repeated across days, prompting many individuals to turn to exercise for obesity treatment (R). Looks great in theory right?
But it doesn’t pan out as great in real life.
Data from the scientific community indicate that a 15-week diet or diet plus exercise program produces a weight loss of about 11 kg with a 60-80% maintenance after 1 year. Not bad right? However, although long-term follow-up data are meager, the data that do exist suggest almost complete relapse after 3-5 years (R). Not so good.
There are quite a few reasons, and a few I already mentioned.
First, some people do it because they feel guilty. Unhealthy exercise is a core symptom of eating disorders that predicts greater chronicity and risk of relapse (R).
Second, excess exercise (and this is very person-specific) can actually increase hunger. Research focused on alterations in hormonal mediators of appetite (e.g.: ghrelin, peptide YY, GLP-1, pancreatic polypeptide, and leptin) have found that exercise can increase hunger and/or reduce satiety to promote greater energy intake. Another reason is because people reward themselves with food; reward-driven feeding (R)
It takes most people between 40 and 60 minutes to expend 500 kcal through exercise, which is about the energy content of a fast-food cheeseburger that can be consumed in 5–10 minutes (R).
Third, when people make a shift from unhealthy eating behaviors and lifestyle things, they start exercising and eating “healthy”. Some people think that because a food is healthy, they can eat tonnes of it. In this scenario, one may decrease their reinforcing value of unhealthy foods and increase their reinforcing value of healthy foods to result in a gross increase in food reinforcement if the increase in healthy foods was greater than the decrease in unhealthy.
This 3rd aspect seems to be what has happened in the above study where the exercise group compensated. What is interesting is that the study found that the increase in calories wasn’t “statistically significant” since the average increase was small. But if you look at the individual variation, it ranged from -340 to 440 calories (R).
If you’re going to overeat on healthy food, you’ll gain weight. If you have lots of cream in your coffee, tonnes of olive oil in your salad, fry your food with lots of butter and add extra butter on your potatoes with a side of rib eye, and have some ice cream (Hazen Dagen anyone), then chances are you’re overeating big time and no amount of exercise is going to save you (from fat land).
Fat free mass, cardio, weight training and hunger
Another possible reason why HIIT is better than low-intensity cardio for fat loss, is because HIIT preserves or even builds muscle.
This study indicating that fat-free mass (FFM) is associated with several brain regions involved in the homeostatic control of food intake, suggesting a centrally mediated mechanism whereby FFM controls satiety (R). This has also been observed in the classic Minnesota Starvation Experiments, where the FFM deficit, independently of FM (fat mass) deficit, predicted the degree of hyperphagia that occurred during post-starvation ad libitum refeeding, which continued until FFM was repleted, often well after FM was restored (R).
Also, aerobic exercise-induced weight loss, especially when coupled with energy restriction, almost always produces concurrent losses in FFM (R).
“Declines in FFM may have the unintended consequence of increasing food reinforcement, causing overeating to promote the return to baseline FFM. Unfortunately, when returning to baseline FFM levels, “fat overshooting” often occurs, where FM is increased beyond baseline levels [55, 60]. Therefore, one can argue that exercise-for weight loss interventions should include resistance exercise to promote, or at least maintain, FFM when attempting weight loss.” (R)
If you’re no obese, then this is a great way to optimize your hormones and stay lean:
Moral of the story, starve yourself or do enough cardio and you’ll start losing muscle mass. A decline in fat-free mass can result in a decrease in satiety, which will lead to reward eating and binging.
If you want to lose weight effectively, do a small deficit, have enough protein and carbs and hit the weights a few times a week. Also, focus on improving your hormonal state and thyroid hormone production.
If you want to do extra cardio, stick to morning walks or some kind of fun activity that is autoregulated and that you can do consistently. Don’t try to add/force 30-60 of cardio every other day to speed things up. If it’s not sustainable, chances are you’ll be back to where you were or even worse after 3 years.
To be successful in the long run, you have to find something that works for you personally and something you can be 80% consistent year after year, decade after decade.
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