Racial Variation in Weight Loss

Yesterday at Obesity 2011, new research about racial variation in weight loss was presented. A behavioral weight loss intervention study looked at whether physical activity and other weight loss behaviors differ between black and white women.

In a previous behavioral modification weight loss program, it was found that black women lost about half the weight white women lost. A group of researchers from Wake Forest, Chapel Hill, and Pittsburgh wanted to look into this finding further, especially since the study was large, well-respected, and conducted by a group recognized for delivering a culturally sensitive program.  In response to the results of this study, this group of researchers set out to determine if black women lose less weight than white, and if so, what are the influencing factors and causes. They tested a group of 94 women, made up of a mix of white and black participants. The average starting Body Mass Index (BMI) of the group was 33 kg/m2.

The researchers conducted a standard behavioral weight loss program, which included a weekly check-in. Participants kept a daily food journal, and were asked to reduce their intake of fat and limit daily calorie intake to 1200 – 1500 kcal (depending on each participant’s starting weight). All of the participants had sedentary lifestyles at the beginning of the study, but built up to about one hour of physical activity daily.  Their activity was measured through a SenseWear Pro Armband.

After 6 months on the program, the white women had lost on average 10.2 pounds, while the black women shed on average 7.4 pounds.  While both groups did show some weight loss, there was a clear difference between the average weight lost by white women compared to the black women. During the study, four measures were used to evaluate each woman’s adherence to the program and guidelines, and no significant differences in adherence were found between the groups. Additionally, the data from the armband showed no significant difference between the women’s activity levels, in several metrics that the researchers examined.

The researchers shared that they think the difference in weight loss between the groups could be due to differences in energy intake (EI), which is the caloric content of all foods taken in, differences in metabolic processes, or perhaps lower resting energy expenditure (REE) – the amount of calories required by the body during a non-active period. They agreed that more work needs to be done to explain the differences. These findings are part of a longer 18 month trial that is just concluding now, with complete data to be presented soon.

Another recent study addressed differences in resting energy expenditure (REE) amongst white and black women.  The study found that body size and composition is an important contributor to REE in white women but that body size and composition in blacks may not be as important a factor for REE. You can read more about the study here.