Getting a Handle on Obesity

Once a problem only in the developed world, obesity is now a
worldwide epidemic. The overwhelming cause of the epidemic is a
dramatic increase in the food supply and in food consumption not a
surprise. Yet there are still many mysteries about weight change
that can.t be answered either inside the lab, because of the
impracticality of keeping people isolated for long periods of time,
or outside, because of the unreliability of dietary diaries.
Mathematical models based on differential equations can help
overcome this roadblock and allow detailed analysis of the
relationship between food intake, metabolism, and weight change.
The models. predictions fit existing data and explain such things
as why it is hard to keep weight off and why obese people are more
susceptible to further weight gain. Researchers are also
investigating why dieters often plateau after a few months and
slowly regain weight. A possible explanation is that metabolism
slows to match the drop in food consumed, but models representing
food intake and energy expenditure as a dynamical system show that
such a weight plateau doesn.t take effect until much later. The
likely culprit is a combination of slower metabolism and a lack of
adherence to the diet. Most people are in approximate steady state,
so that long-term changes are necessary to gain or lose weight. The
good news is that each (enduring) drop of 10 calories a day
translates into one pound of weight loss over three years, with
about half the loss occurring in the first year. For More
Information: Quantification of the effect of energy imbalance on
bodyweight, Hall et al. Lancet, Vol. 378 (2011), pp. 826-837.