The present study tests the hypothesis that specific endocrine, metabolic and anthropometric features distinguish obese women with polycystic ovary syndrome (PCOS) who resume ovulation in response to calorie restriction and weight loss from those who do not. 15 obese (body mass index 39±7 kg/m²) hyperandrogenemic oligo-ovulatory patients undertook a very low calorie diet (VLCD), wherein each lost at least 10% of bodyweight over a mean of 6.25 months. Body fat distribution was quantitated by magnetic resonance imaging. Hormones were measured in the morning at baseline, after one week of VLCD and after 10% weight loss. To monitor luteinizing hormone (LH) release, blood was sampled for 24h at 10 min intervals prior to intervention and after 7 days of VLCD. Responders were defined a priori as individuals exhibiting two or more ovulatory cycles in the course of intervention as corroborated by serum progesterone concentrations 18 nmol/l followed by vaginal bleeding. At baseline, responders had a higher sex hormone-binding globulin (SHBG) concentration, but were otherwise indistinguishable from non-responders. Bodyweight, the size of body fat depots and plasma insulin levels declined to a similar extent in responders and non-responders. Also, SHBG increased and the free testosterone index decreased comparably. However, responders exhibited a significant decline of circulating estradiol concentrations (from 191 ± 82 to 158 ± 77 pmol/L, mean ± SD, P = 0.037) and a concurrent increase in LH secretion (from 104 ± 42 to 140 ± 5 U^.L^-1.day^-1, P = 0.006) in response to 7 days of VLCD, whereas neither parameter changed significantly in non-responders. We infer that evidence of retention of estradiol-dependent negative feedback on LH secretion may forecast follicle maturation and ovulation in obese patients with PCOS under dietary restriction.