Quantification of the Effect of Energy Imbalance on Bodyweight

A fundamental principal of nutrition stipulates that bodyweight changes occur when there is an imbalance between the energy content of food consumed and the energy expended to maintain life and perform work. Any successful obesity intervention needs to quantify the effect of both energy in and energy out over time.

The conventional rule for weight loss—cut 500 calories a day for a week and lose a pound of weight—is too simplistic. It doesn't take into account the dynamics of a changing baseline (as you loose weight you need less calories to sustain weight), and individual body composition (fat tissue and muscle tissue metabolize food differently). Any small but persistent deviation in energy intake translates into weight loss—or more frequently, weight gain.

With few methods for accurately predicting how changes in diet and physical activity translate into weight changes over time, this research group developed and validated various mathematical models of human metabolism and weight change. Their Web-based simulator allows individuals to set weight loss goals and see how combinations of diet and exercise can achieve results—and in what time frame. Extrapolating to a population, the model provides insights into how energy imbalances are responsible for today’s obesity epidemic.