If you eat less and move more, you start to lose weight. Your body is in a state called ‘negative energy balance’ in which energy input is smaller than output. There are many ways to reach the negative balance and depending on how to reach the state, outcomes vary.

If it is just by eating less than you move, you lose more muscle than fat. It is because our body has been evolved to keep fat as long as it can so that it wouldn’t just let go of fat. On the other hand, muscle is an expensive tissue to maintain. Muscle consumes about 40 percent of your body’s resting metabolism and the body is well aware of that. Body is an efficient organism and if it sees no point of keeping muscles, it would readily break them down and use the resources elsewhere.

Therefore, by creating a gap between energy input and output, you lose more muscle than fat. It already sounds bad enough, but hold on, it’s only a beginning.

Your body weight is most likely to return to your “normal” weight. It is because you ended up with less muscles, which makes your body susceptible to gain weight. And because your body knows you are not giving enough food recently, it tends to absorb better, then save more. (It is called carbohydrate loading.)

And when the weight bounces back, what weight would you gain? Muscle or fat?

This time, in a somewhat unfairly fashion, you gain more fat than muscle. Because, after all, we know it is hard to gain muscle even with exercise and taking protein, and your body already knows you don’t need much muscle anyway. (That’s why it discarded them in the first place.)

What happens if you repeat this process once a year? Ten years from now, you may be at the same weight as you are now, but the shape of your body will be totally different. After ten times of trading valuable muscle with unwanted fat, fat areas grow larger and muscles get thin. And it will be noticeable, because the same weight of fat is larger than muscle.

And noticeable, because the body likes to reserve fat at certain spots. For women, it is hip and legs, and for men, it is belly. So those spots get disproportionately fatter. That is why people in their 40s and 50s may be at the same weight as in their 20s, but their body doesn’t look the same.

Many of my female trainees talked about the good old days of skipping a few dinners and keeping their waist thin. That is possible because when you are young, you enjoy a high level of growth hormone secretion and the hormone drives muscle growth and fat loss. That is why baby and kid can gain muscle and strength, basically, grow, without lifting weights. But once you reach adulthood and the hormone secretion drops, the trick doesn’t work and, if anything, pushes you into the vicious cycle.

So what should we do then? Is there a better way to lose weight without getting into this vicious cycle? Answer: Take advantage of the energy-burning factories.