Reversing the obesity epidemic will take time

Weight loss is a complex thing. In fact, the old rule that cutting out or burning 500 calories a day will result in a steady, 1-pound-per-week weight loss doesn’t reflect real people, researchers say.

A new mathematical model from researchers at the National Institutes of Health instead shows that for the typical overweight adult, every 10-calorie-per-day reduction will result in the loss of about 1 pound over three years. Half that loss will occur in the first year. For example, cutting 250 calories a day from one’s diet will lead to a 25-pound weight loss over three years. This is a more realistic model than the traditional rule-of-thumb, the authors said.

The new model provides a more realistic assessment and uses data relating to how energy expenditures change over time. Moreover, people are different. Heavier people will lose weight more rapidly than their less-obese counterparts but will take longer to achieve a stable weight.

The study demonstrates how the average 20-pound increase in the average adult’s body weight occurred over the last 30 years in the United States. That weight gain amounts to only an extra 10 calories a day. But equally small reductions in calories won’t lead to the same weight loss, the authors point out. In fact it takes an average of 220 extra calories a day to maintain people at their higher weight.

That’s why a dedicated, long-term change is needed to reverse the obesity pandemic. For adults with a body mass index of more than 35, which is obese, it would take permanent calorie reductions of more than 500 calories a day to return them to the average body weight seen in the United States in 1978. This would take about three years for moderately obese people and longer for severely obese people.

The research is part of a special issue of the Lancet published Thursday on the global obesity pandemic. In other studies, researchers show how obesity affects people around the world. In developing nations, obesity tends to appear first in middle-aged adults, especially women. In high-income countries, both sexes and all ages tend to be affected by obesity. However, obesity is more prevalent in poorer people.

But, the authors wrote: “No country can act as a public health exemplar for reduction of obesity and type 2 diabetes.”

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