Effects of Fasting on Neuroendocrine Function and Follicle Development in Lean Women 1

Abstract

A 72-h fast in normal weight women during the follicular phase results in transient alterations in neuroendocrine function, but follicle development and follicular phase length remain unaltered. In this study we evaluated neuroendocrine and ovulatory function in lean women (body fat, < 0.05). Fasting did not result in significant differences in mean LH, LH amplitude, LH area under the curve, and mean FSH levels in these lean women. Of the seven fasted cycles, two were anovulatory. In the five women studied in fed and fasted cycles, one had interrupted lead follicle development with anovulation, and four had significant lengthening of the follicular phase compared to those during their fed cycles (14.4 +/- 1.2 vs. 13.2 +/- 1.0 days; P = 0.01). The clinical observations made in this small sample of lean women showing more profound changes in neuroendocrine function, anovulation, and lengthened follicular phase after fasting suggest that lean women may be more vulnerable to fasting stress than normal weight women.