The problem is people take that idea and they extrapolate it to think that telling someone to eat less and exercise more is an effective strategy to cause an overweight person to become lean, and that’s where you have a disconnect because there are other factors in the equation.
The body is not static. It reacts to changes in energy intake and energy expenditure by trying to compensate. So that’s the issue. If you eat fewer calories, your body activates a program that tries to conserve those calories.
Dr. Stephan Guyenet, Ph.D, obesity researcher at the University of Washington