(Reuters Health) - African American women who follow the same diet as white women and exercise just as much tend to lose less weight because they burn fewer calories, a new study suggests.
"Many large and well done studies have demonstrated that African American women tend to lose fewer pounds than their Caucasian counterparts," Dr. Ann Smith Barnes told Reuters Health by email.
Smith Barnes studies obesity at Baylor College of Medicine and is the medical director of Weight Management Services and Disease Prevention for the Harris Health System of Houston. She was not involved in the new study.
Scientists haven't been sure what explains those differences in weight loss. One suggestion is that African American women are less likely to adhere to weight loss programs. Another possible explanation is that their bodies need fewer calories.
To learn more, James DeLany from the University of Pittsburgh and his colleges studied 39 African American women and 66 white women. The participants were all severely obese and were randomly assigned to either a calorie-restricted diet alone or the diet along with exercise guidelines.
The researchers measured women's daily energy expenditure at the beginning and end of the study. They also tracked their physical activity using wearable monitors.
By the end of the six-month intervention, white women had lost an average of 24 pounds and African American women had lost an average of 16 pounds, according to findings published in the International Journal of Obesity.
But the African American women had increased their physical activity by as much as white women and they followed the prescribed diet just as closely.
"Our results show that the African American women and Caucasian women were consuming nearly exactly the same number of calories during the intervention, and were engaged in the same amount of physical activity - they were as compliant as the Caucasian women," DeLany told Reuters Health in an email.
His team calculated women's energy requirements and found African American participants needed less energy than white participants.
"The reason the African American women lost less weight than the Caucasian women is because the prescribed caloric intake for most interventions, including our study, is based on initial body weight, and since the African American women have lower energy requirements than Caucasian women of the same weight, they were prescribed a lower caloric restriction during the intervention," DeLany said - meaning their diet wouldn't have been as intensive.
DeLany said that according to his findings, African American women would have to eat about 150 fewer calories per day than their white peers - or work out that much more - to lose the same amount of weight.
"This new study has a small sample of participants, so cannot be widely generalized," Smith Barnes said. "However, it does add to our understanding of possible reasons for differences in the number of pounds lost between different ethnic groups and helps to dispel the notion that African American participants are necessarily less compliant than Caucasians in behavioral change interventions."
"What is a more interesting question is whether the weight loss that is achieved among African Americans - even if less than Caucasians - produces equal health benefits in blood pressure, glucose, cholesterol, and other weight-sensitive chronic conditions," she said.
Smith Barnes said some studies suggest behavioral changes - and not just weight loss - are what matter for improving health.
"More research needs to be done to confirm this, but if it is true, then the number of pounds lost would be less important from a health standpoint," she added.
Smith Barnes said her research has shown African American women who lose extra weight and keep it off tend to follow three strategies: reduce fat intake, avoid fast food and weigh themselves regularly.
SOURCE: bit.ly/1d56IgM International Journal of Obesity, online December 19, 2013.