Tom notes this piece on the failure of weight control strategies.
At some point physics is correct - energy is conserved. The problem is the nature of energy utilization and expenditure aren't well known and that is people who have dieted the natural mechanism for regulation seems to be reset to an improper point. We seem to have evolved to store weight to get us through lean periods.
For most people the largest lever is how many Calories you eat, but exercise is also important and may be invovled in regulation.
This paper is a call for both approaches - caloric restriction and greater physical activity - to be used
Using an exhaustive review of the energy balance literature as the basis, the researchers also refuted the popular theory that escalating obesity rates can be attributed exclusively to two factors -- the change in the American diet and the rise in overall energy intake without a compensatory increase in energy expenditure. Using rough estimates of increases in food intake and decreases in physical activity from 1971 to 2000, the researchers calculated that were it not for the physiological processes that produce energy balance, American adults would have experienced a 30 to 80 fold increase in weight gain during that period, which demonstrates why it is not realistic to attribute obesity solely to caloric intake or physical activity levels. In fact, energy expenditure has dropped dramatically over the past century as our lives now require much less physical activity just to get through the day. The authors argue that this drop in energy expenditure was a necessary prerequisite for the current obesity problem, which necessitates adding a greater level of physical activity back into our modern lives.
"Addressing obesity requires attention to both food intake and physical activity, said co-author John Peters, PhD., assistant director of the Anschutz Health and Wellness Center. "Strategies that focus on either alone will not likely work."
In addition, the researchers conclude that food restriction alone is not effective in reducing obesity, explaining that although caloric restriction produces weight loss, this process triggers hunger and the body's natural defense to preserve existing body weight, which leads to a lower resting metabolic rate and notable changes in how the body burns calories. As a result, energy requirements after weight loss can be reduced from 170 to 250 calories for a 10 percent weight loss and from 325 to 480 calories for a 20 percent weight loss. These findings provide insight concerning weight loss plateau and the common occurrence of regaining weight after completing a weight loss regimen.
Recognizing that energy balance is a new concept for to the public, the researchers call for educational efforts and new information tools that will teach Americans about energy balance and how food and physical activity choices affect energy balance.
An interesting question I have is has any country developed a signficant program that has had a lasting, significant and cost effective impact? Some countries - notably the Netherlands and Denmark - partly justify active transportation infrastructure (walking and biking) by improved health rates, but obesity prevention is only part of that puzzle.