Subjects with abdominal obesity are characterized by hyperactivation of the hypothalamic-pituitary-adrenal (HPA) axis. Food intake, particularly at noon, is a well-known inducer of HPA axis activation. Whether obese subjects present an abnormal response to meals containing different macronutrient proportions is at present unknown. Therefore, this study was carried out to investigate the effect of a high-lipid/protein meal (HLP-meal) and a high-carbohydrate meal (HCHO-meal) on the HPA axis activity in women with different obesity phenotypes. Nondepressed, noncomplicated obese (body mass index greater than 28 kg/m2) women with abdominal (A-BFD) (n = 10) and peripheral body fat distribution (P-BFD) (n = 9) and a group of 11 normal-weight controls were investigated in the follicular phase of the menstrual cycle. They were randomly given an 800-kcal HCHO-meal (containing 89% carbohydrates, 11% proteins, 0% lipids), and an 800-kcal HLP-meal (containing 53% lipids, 43% proteins, 4% carbohydrates), which were eaten within 15 min at noon, with an interval of 2 d between each meal. Blood samples for ACTH, cortisol, glucose, and insulin were obtained at 15-min intervals before and after each meal. Baseline hormone and glucose concentrations in the three groups were similar. After the HLP-meal, ACTH tended to similarly but insignificantly increase in all groups, whereas cortisol increased significantly (P < 0.05) in the P-BFD group and insignificantly in the other groups. Conversely, both ACTH and cortisol significantly (P < 0.05) increased only in the A-BFD group, without any significant changes in both controls and P-BFD women. The analysis of the interaction between meals and groups clearly indicated that the cortisol response to the HLP-meal and the HCHO-meal was significantly different (P < 0.025) between the two obese groups, the A-BFD group being characterized by a significantly lower response to the HLP-meal and a significantly higher response to the HCHO-meal, compared with the P-BFD group. Considering all groups together and after adjusting for body mass index, a highly significant relationship was found between cortisol-area under the curve and ACTH-area under the curve after each meal test. However, no relationships were found between changes in ACTH and cortisol and those of glucose, insulin, and the glucose:insulin ratio after each meal. Therefore, our data demonstrate that the response of the HPA axis to meals containing different macronutrient proportions may depend on the pattern of body fat distribution. We also suggest that the activation of the HPA axis following the ingestion of large amounts of carbohydrates may have some pathophysiological relevance, specifically in women with the abdominal obesity phenotype.
Response of the Hypothalamic-Pituitary-Adrenocortical Axis to High-Protein/Fat and High-Carbohydrate Meals in Women with Different Obesity Phenotypes