Isn’t it obvious that the only way to lose fat is to burn more calories, and that to burn more calories we need to exercise more? The only thing that makes it obvious is that we all believe it to be the case. Interestingly, it isn’t. Well, actually, it isn’t quite the case.
It’s easy to see the point when considering an extreme example. Imagine a morbidly obese person who decides to start fasting, and to simply stop eating until they are no longer obese. There is an important historical example of this. And it is historical because it was recorded and documented from beginning to end. It holds the record for the longest fast. Angus Barbieri fasted during 382 days, and lost 125 kg. Do you think he had to exercise to lose these 125 kg of body fat?
Is that an unfair example in some way because it’s obvious that if we stop eating we will for sure lose body fat? If this is obvious, then why do we hold the belief that we need to exercise more in order to lose body fat? It should be clear that it isn’t necessary. Let us now get to the underlying mechanism.
The first thing that happens when we stop eating, is that blood sugar concentration drops. What follows is that insulin concentration also drops. Insulin is a hormone that signals the presence of plenty, and that it would be wise to store the nutrients circulating in the bloodstream for later when there aren’t any. Low insulin levels signals the opposite: that there isn’t much available, and that reserves should be tapped into to supply the energy needed by our cells to function.
It is therefore this—low insulin concentration—that is required to create the conditions to lose body fat.
But what about calories burnt while we exercise? An average person needs between 1500 (small woman) to 3000 (tall man) calories per day. The same average person running 30 minutes, (and how many people do you actually know who can run 30 minutes?), will burn about 250 to 450 calories. But a medium size blueberry muffin is about 425 calories. A large handful of walnuts has about 370 calories. Do you really think that running 30 minutes, even if you do it every day, is enough to significantly offset our daily calorie balance? It isn’t.
The effect of exercise on body composition is not directly but indirect. Exercise will both increase the sensitivity of the muscle cells to insulin, making them more efficient at using glucose. Exercise will also increase body temperature and metabolic rate, both of which will increase how much energy is used by our cells, for several hours following exercise. And the most effective kind of exercise in this respect is resistance training, or more plainly, weight lifting.
The most metabolically active tissue is muscle. The more muscle we have, the more energy is used, and the faster both glucose and fat are burned to supply fuel to the cells. The more we use our muscles, and the more intensely we use them, the more they grow, and the more efficiently they burn both glucose and fat. Also, the stronger the muscles, the stronger and denser the bones will be. This is very important.
Therefore, as we burn more fat, we burn fat more efficiently. As we use our muscles more intensely, we burn more fat. And as we build more and stronger muscle, we burn even more fat even more efficiently, and make the bones stronger.
Hence, the essential key to fat loss is low insulin. Exercise is not necessary, and the way it helps is not with the amount of calories it burns, but in the indirect effect on glucose usage, insulin sensitivity, and metabolic rate. And the most metabolically effective way to work muscles is with resistance training by lifting weights.
G. Belanger, PhD — Kalibra Co-Founder and CSO