Is it true that the body gets used to diet and exercise after a while and stops responding?

Question

I am currently reading a book called "The Body Sculpting Bible for Men" by James Villepigue and Hugo Rivera. In it the author claims that when you start dieting your body receives a shock from the immediate decrease in calories and you lose weight fast. After about two weeks the shock wears off, your body becomes accustomed to the change in diet. It starts to slow down metabolism to conserve energy since the caloric intake is lower now. So instead of continuing to lose fat you just become more lethargic and the fat stops burning. He claims the same thing about exercise routines. Stating that both diets and exercise regimens need to be changed up every couple of weeks to make sure the body doesn't get accustomed to either. For example he suggests that you alternate between high and low calorie diets biweekly. Only in this way can one lose weight and gain muscle consistently.

Is this true?

Answer 1

Well the first part is true for some people. It's a fact that not everyone responds to diet and exercise the same way, and that's a reasonable hypothesis for why some people react in a certain way.

The last part about alternating high and low calorie diets being the only way to lose weight and gain muscle consistency isn't true. For weight loss it might certainly be a way that works for some people, but it's not going to be the only way that works either.

As far as losing weight consistently goes, I've seen numbers of as high as 95% of people who lose weight return to their original weight (or higher!) within a year, and that's regardless of specific method used.

As far as muscle gain goes, you don't need to switch things up. There the science and evidence is pretty solid. Progressive overload leads to progressive strength gains and progressive strength gains lead to progressive muscle gains. If you're lifting weights, getting enough rest in between sessions and gradually increasing the amount you're lifting, you'll get stronger, and your muscles will get bigger. How much stronger and how much bigger will depend on your genetics and how suitable the method you're using is, but the principle stays the same.

The biggest obstacle, aside from overtraining, to sustained progressive weight overload is that at a certain point a 5lbs or 10lbs jump in weight becomes a bit too much. Eventually you're going to be increasing in increments of 2lbs, 1lbs or even 8oz, and then finally at your absolute max you'll stop making gains at all. Once you hit that, switching it up isn't really going to help for strength, but that doesn't mean you should branch out. It's not going to be after 2 weeks that you'll need to change your strength building routine though.