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Physical activity may count more for women who keep the pounds off



Women who successfully maintained weight loss burned a greater proportion of their daily calories through physical activity than did controls with either normal or high body mass, but the same effect wasn’t seen in men, according to new analysis of a small study.

Dr. Ann Caldwell, University of Colorado Anschutz Medical Campus, Aurora Kari Oakes/MDedge News

Dr. Ann Caldwell

Physical activity is a key component in successful maintenance of weight loss, but differential effects of physical activity between men and women had not been well explored, Ann Caldwell, PhD, said in an interview at Obesity Week 2018, presented by the Obesity Society and the American Society for Metabolic and Bariatric Surgery.

Dr. Caldwell and her colleagues at the University of Colorado Anschutz Medical Campus, Aurora, conducted a secondary analysis of case-control data of individuals with healthy weight, overweight, or obesity, and those who had successfully maintained weight loss. They compared total daily energy expenditure (TDEE) and physical activity energy expenditure (PAEE), looking at men and women in all three groups separately.

The study included 20 women and 5 men who had successfully maintained a weight loss of at least 13.6 kg for at least 1 year. These were matched with 20 women and 7 men with a body mass index within the healthy range, as controls for the weight loss maintainers at their post–weight loss BMI.

Another group of 22 women and 6 men with BMIs in the overweight or obese category served as controls for the weight loss maintainers at their pre–weight loss BMI.

For all participants, TDEE was measured using the doubly labeled water method for 7 days. This method tracks elimination of a set quantity of ingested water made up of two uncommon isotopes (hydrogen-2 and oxygen-18) to measure energy expenditure. Since the oxygen is lost both as water and carbon dioxide as a result of metabolism, the presence of less oxygen-18 over time indicates a higher total energy expenditure.

Indirect calorimetry was used to measure resting energy expenditure (REE), and energy expenditure related to physical activity was calculated by subtracting REE and a 10% fraction of TDEE (to account for the thermic effect of feeding) from total TDEE.

“There were significant sex-group interactions for TDEE, PAEE, and PAEE/TEE,” said Dr. Caldwell. She explained that the cutoff for statistical significance for the investigators’ analysis was set at P = .1, since sample sizes were so small for men.

For women who were weight-loss maintainers, both PAEE and PAEE/TDEE ratios were higher than for the female healthy-BMI and high-BMI control participants: PAEE was 822 kcal/day for the maintainers, 536 kcal/day for the healthy-BMI, and 669 kcal/day for the high-BMI controls (P less than .01 for both comparisons).

Dr. Caldwell and her colleagues saw no difference when comparing the PAEE/TDEE ratio for women in each of the control groups.

For men, by contrast, PAEE was highest for those with healthy BMIs, at 815 kcal/day, and lowest for those in the high-BMI control group, at 506 kcal/day. Men who were weight loss maintainers fell in the middle, at 772 kcal/day of PAEE. The PAEE/TDEE ratio was significantly higher for both weight loss maintainers and normal-BMI participants than for the high-BMI participants (P less than .07).

“These cross-sectional data suggest potential sex differences in the importance of [physical activity] for successful weight loss maintenance that should be explored further with objective measures,” wrote Dr. Caldwell and her coauthors.

The investigators are planning further work that incorporates objective physical activity data via actigraphy, and that will include a larger sample of men. Through a prospective study that overcomes the limitation of the present study, they hope to develop a clearer picture of sex differences in weight loss maintenance.

The National Institutes of Health supported the study. Dr. Caldwell reported no relevant conflicts of interest.

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SOURCE: Caldwell A et al. Obesity Week 2018, Abstract TP-3233.

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