Effects of race, cigarette smoking, and use of contraceptive medications on resting energy expenditure in young women.

The prevalence of obesity is higher in Black women than in White women (JAMA 1994;272:205-11; Arch Pediatr Adolesc Med 1995;149:1085-91). Although it has been shown that Black women have a lower resting energy expenditure (REE), factors affecting REE remain unclear. This 1996-1997 study in Cincinnati, Ohio, assessed racial differences in REE and their determinants in a biracial cohort of 152 healthy young women aged 18-21 years. Two indirect calorimetric measurements were obtained during two overnight hospital admissions 10-14 days apart. Body composition was measured by using dual-energy x-ray absorptiometry. Mean REE (adjusted for body composition, smoking, and contraceptive medication use) was significantly (p = 0.04) lower by 71 kcal/day in Black women (1,453 (standard error, 21) kcal/day) than in White women (1,524 (standard error, 19) kcal/day). Smoking was associated with a REE that was 68 kcal/day higher for both groups (p = 0.03). A trend (p = 0.07) toward increased REE (by 46 kcal/day) was found with contraceptive medication use. In conclusion, young Black women had a significantly lower REE than did White women. Cigarette smoking significantly increased REE. The apparent presence of a more parsimonious energy metabolism in Black women suggests that maintenance of energy homeostasis requires particular vigilance in this high-risk population.