RESUMO
CONTEXT: Obesity is associated with neuroendocrine reproductive alterations and decreased fertility. OBJECTIVE: The objective of the study was to gain insight into the neuroendocrine mechanisms implicated in these alterations. DESIGN: The effects on pulsatile LH secretion of 28 days of a hypercaloric diet were studied in lean and regularly cycling female volunteers. Approximately 50% extra calories (3 g sucrose/kg body weight per day and 1 g fat/kg body weight per day) were added to their individual daily requirements. Spontaneous and insulin-stimulated LH secretion was recorded on 2 different days, before and at the end of the caloric load. RESULTS: The hypercaloric diet induced an average weight gain of 2.0 ± 0.3 kg (P < .05), corresponding to a body mass index increase of 0.7 ± 0.1 kg/m(2) (P < .05). A concomitant decrease of 11.6% ± 4.6% in whole-body insulin sensitivity was also observed (δ = -1.6 ± 0.7 mg/kg · min glucose; P < .05). The frequency of spontaneous and insulin-stimulated pulsatile LH secretion was increased by 17.9% ± 9.0% and 26.5% ± 9.0%, respectively (both P < .05). Spontaneous LH peak amplitude was decreased by 26.5% ± 9.0% (δ = -0.7 ± 0.36 U/L; P < .05), a change correlated with insulin sensitivity. CONCLUSIONS: Short-term weight gain in normal female volunteers induces alterations of LH secretion reminiscent to those observed in obesity. A decrease in insulin sensitivity may constitute a mechanistic link between obesity and its associated neuroendocrine dysfunctions.