Exercise more important than diet to maintain weight loss

Physical activity helps maintain significant weight loss more effectively than diet, according to a recent study from the University of Colorado Anschutz Health and Wellness Centre (AHWC) at the CU Anschutz Medical Campus. The study, published in the March issue of Obesity, was selected as the Editor's Choice article.

"This study addresses the difficult question of why so many people struggle to keep weight off over a long period. By providing evidence that a group of successful weight-loss maintainers engages in high levels of physical activity to prevent weight regain -- rather than chronically restricting their energy intake -- is a step forward to clarifying the relationship between exercise and weight-loss maintenance," said Danielle Ostendorf, PhD, a postdoctoral fellow at the CU Anschutz Health and Wellness Centre.

The findings reveal that successful weight-loss maintainers rely on physical activity to remain in energy balance (rather than chronic restriction of dietary intake) to avoid weight regain.

In the study, successful weight-loss maintainers are individuals who have been maintaining a reduced body weight of 30 pounds or more for over a year.

"Our findings suggest that this group of successful weight-loss maintainers are consuming a similar number of calories per day as individuals with overweight and obesity but appear to avoid weight regain by compensating for this with high levels of physical activity," said Victoria A Catenacci, MD, a weight management physician and researcher at CU Anschutz Medical Campus.

The study looked at successful weight-loss maintainers compared to two other groups: controls with normal body weight (body mass index or BMI) similar to the current BMI of the weight-loss maintainers); and controls with overweight or obesity (whose current BMI was similar to the pre-weight-loss BMI of the maintainers).

The weight-loss maintainers had a body weight of around 150 pounds, which was similar to the normal weight controls, while the controls with overweight and obesity had a body weight of around 213 pounds.

This study is one of the few to measure total daily energy expenditure in weight-reduced individuals using the gold standard doubly labelled water method. This method allows researchers to precisely determine an individual's energy expenditure through collecting urine samples over one to two weeks after people are given a dose of doubly labelled water.

Doubly labelled water is water in which both the hydrogen and the oxygen atoms have been replaced  with an uncommon isotope of these elements for tracing purposes.

The measure of total daily energy expenditure from doubly labelled water also provides an estimate of energy intake when people are weight stable, as they were in this study. Prior studies used questionnaires or diet diaries to measure energy intake, which have significant limitations.

The researchers also measured each individual's resting metabolic rate in order to understand how much of the total daily energy expenditure is from energy expended at rest versus energy expended during physical activity. Prior studies used self-reported measures or activity monitors to measure physical activity, which are techniques that cannot provide the same accuracy.