short communications integrative physiologyLeptin, an anorexigenic hormone, assists in regulation of energy balance (1). Secreted by adipocytes, leptin binds to hypothalamic leptin receptors to initiate a cascade of regulatory signals that control food intake (2). Individuals with excess adiposity have higher circulating leptin concentrations than lean people (3,4); however, leptin resistance has been demonstrated in humans with excess adiposity, suggesting impaired receptor function and disrupted cessation of food ingestion (5,6).Systemic leptin concentration changes in response to alterations in body fat mass (FM) in humans (7,8). Serum leptin may respond more favorably to FM losses induced by a lowcarbohydrate (LC) diet compared to a low-fat (LF) diet (9-11), although this is ambiguous (12). Distribution of FM (i.e., central vs. peripheral) may affect the systemic leptin concentration and response to dietary approaches to body weight (BW) loss. Therefore, the purpose of this study was to examine serum leptin concentrations in women undergoing BW reduction by one of two dietary approaches. Changes in total body (TB) FM and central abdominal fat (CAF) in relation to changes in serum leptin were evaluated within diet groups. It was hypothesized that women consuming a LC, high-protein (LCHP) diet for BW loss would have a significantly greater reduction in serum leptin concentration compared to women consuming a high-carbohydrate, LF (HCLF) diet. Moreover, the association between change in TB FM and CAF and change in serum leptin concentration would be stronger in the LCHP vs. HCLF diet group.
Methods And ProceduresThe Institutional Review Board for Research Involving Human Subjects at Virginia Tech approved this study. Informed consent was obtained from each woman before participation. Subjects were recruited by wordof-mouth and through posted announcements on the Virginia Tech campus. Women were included if BMI at screening was ≥25 and ≤40 kg/ m 2 , and they were weight stable for the past year, eumenorrheic, nonpregnant, nonlactating, without endocrine or metabolic diseases, and cleared by their primary care physicians to participate.Twenty-five free-living women (age = 39.4 ± 3.4 years; height = 163.6 ± 5.9 cm; weight = 81.9 ± 14.9 kg; BMI = 30.5 ± 5.1 kg/m 2 ) were randomized to one of two diets. Thirteen women followed a LCHP diet. During the first 2 weeks, these women consumed ≤20 g carbohydrate per day. During weeks 3 through 10, carbohydrate intake increased by 5 g per week until 60 g carbohydrate per day was reached, and in the final 2 weeks, women in the LCHP diet group consumed 60 g carbohydrate per day. Liberal amounts of dietary protein and fat were allowed, and total energy intake was not restricted in the LCHP group (13). Leptin may favorably respond to fat mass (FM) losses induced by a low-carbohydrate (LC) diet, although this is unclear. We examined serum leptin concentrations in women in midlife undergoing different dietary approaches to body weight (BW) loss. Women followed either a LC, high-pr...
