Associations of leptin, insulin resistance and thyroid function with long-term weight loss in dieting obese men

Objective. The aim of the present study was to identify predictors of weight loss in obese men participating in a 2-year behaviour modification programme. Design. Longitudinal, clinical intervention study of a behaviour modifying weight loss program. Setting. University Hospital, Stockholm, Sweden Subjects. Forty-four obese men (age, 42.7 +/- 1.1 years; BMI, 37.1 +/- 0.6 kg m(-2), mean +/- SEM) followed for 2 years. Interventions. Behaviour modification weight loss programme. Main outcome measures. Associations between plasma leptin and thyroid function tests, insulin resistance by homeostatic model assessment (HOMA), dietary recall and anthropometrically determined body composition. Results. At baseline, there were significant correlations between plasma leptin and body mass index (BMI), fat-free mass (FFM) and insulin resistance. Median weight loss over 2 years was 4.9 kg (range, - 27.2 to + 11.9). Baseline serum leptin concentrations adjusted for BMI (leptin/BMI ratio) were significantly correlated with 2-year weight change (r = 0.34, P = 0.04). A subset of seven of the 44 men gained weight over the 2 years. These 'gainers' differed significantly in initial leptin/BMI ratio (0.62 +/- 0.07) compared with the 37 'losers' (0.42 +/- 0.03, P < 0.05). In a multiple regression model, baseline leptin, insulin and age predicted 22% of the variance in weight change with no additional significant contribution from BMI, FFM, waist:hip ratio, thyroid function tests or energy intake. There was a strong correlation between the change in leptin concentrations and the change in insulin resistance from baseline to 2-year follow-up (r = 0.54; P < 0.001). Conclusion. Baseline plasma leptin concentrations predicted long-term weight loss. Inappropriate leptin secretion or disposal, corrected for BMI, was associated with failure to maintain weight loss in obese men in a behaviour modification weight loss programme.