Slower calorie burn for obese black mothers during pregnancy
A study published in The FASEB Journal found that obese African-American women have significantly lower energy expenditure per kilogram of mass compared to obese white women with similar energy intake and physical activity levels. The researchers believe the findings illustrate a need for updated weight gain recommendations for obese women with a more individualized focus.
In the study, 34 black and 32 white women (n=66) with obesity were included. The women had a similar body mass index (BMI) (36.9±0.7 kg/m2), body fat percentage (55.1±1.1 kg, P = 0.009) and age (27.7±0.6 years). A BMI of 30 or above at the start of pregnancy is considered obese. Metabolic and behavioral phenotyping for the study took place between 14 and 16 weeks’ gestation. Energy expenditure was measured in free-living conditions over 1 week using stable isotopes and a room calorimeter during sleep. Body composition was measured using air displacement plethysmography. Physical activity was measured using accelerometers.
The researchers found that the African-American participants had more fat-free mass than the white participants (56.9±1.6 vs 51.6±1.1 kg, P = 0.06). In addition, total daily energy intake was significantly lower in the African-American participants than in the white participants (2633±88 vs 2901±76 kcal/d, P = 0.03). Initial results showed that food intake and total daily energy expenditure (TDEE) were not different between the two groups (2590±77 vs 2711±56 kcal/d, P = 0.21). But after correction for individual differences in body composition, the researchers found that TDEE was significantly lower in African-American women (-231±74 kcal/d, P = 0.003). African-American women also had lower energy expenditure during sleep after adjusting for body composition (-81±37 kcal/d, P = 0.03). Daily activity levels and composition of diet in the two groups were similar.
The researchers believe their findings could have an impact on the current non-race-specific caloric intake guidelines for pregnant women, specifically for energy intake during pregnancy. Because the findings show that African-American mothers expend a lower amount of energy, the current guidelines may lead to unintentional overeating and contribute to the increasing prevalence of excessive gestational weight gain in this population.