James O. Hill and colleagues at the Anschutz Health and Wellness Center at the University of Colorado School of Medicine said they focus on energy balance -- combining food intake, energy expended through physical activity and energy, or fat, storage -- to advance the concept of a "regulated zone."
Using this strategy, the mechanisms by which the body establishes energy balance are managed to overcome the body's natural defenses toward preserving existing body weight, Hill said.
"A healthy body weight is best maintained with a higher level of physical activity than is typical today and with an energy intake that matches," Hill said in a statement. "We are not going to reduce obesity by focusing only on reducing food intake. This strategy hasn't worked so far and it is not likely to work in the future."
People who don't move around much have trouble achieving energy balance because they must constantly use food restriction to match energy intake to a low-level of energy expenditure, Hill explained.
The findings, published in the journal Circulation, said constant food restriction is difficult to maintain long-term and when it cannot be maintained, the result is positive energy balance -- when the calories consumed are greater than the calories expended -- and an increase in body mass, of which 60 percent to 80 percent is usually body fat.