SERUM LEPTIN CONCENTRATION, OBESITY, AND INSULIN-RESISTANCE IN WESTERN SAMOANS - CROSS-SECTIONAL STUDY

Objective-To measure serum leptin concentrations in the Polynesian pop ulation of Western Samoa and to examine epidemiological associations o f leptin with anthropometric, demographic, behavioural, and metabolic factors in this population with a high prevalence of obesity and non-i nsulin dependent diabetes mellitus. Design-Cross sectional study, lept in concentration being measured in a subgroup of a population based sa mple. Subjects-240 Polynesian men and women aged 28-74 years were sele cted to cover the full range of age, body mass index, and glucose tole rance, Main outcome measurements-Serum leptin, insulin, and glucose co ncentrations; anthropometric measures; physical activity; and area of residence. Results-Leptin concentrations were correlated with body mas s index (r = 0.80 in men, 0.79 in women) and waist circumference (r = 0.82 in men, 0.78 in women) but less so with waist to hip ratio, At an y body mass index, leptin concentration was higher in women than men ( geometric mean adjusted for body mass index 15.3 v 3.6 pg/l, P < 0.001 ). Leptin concentration also correlated with fasting insulin concentra tion (r = 0.63 in men, 0.64 in women) and insulin concentration 2 hour s after a glucose load (r = 0.58 in men, 0.52 in women). These associa tions remained significant after controlling for body mass index; effe cts of physical activity and of rural or urban living on leptin concen tration were eliminated after adjusting for obesity, except values rem ained high in urban men. 78% of variance in leptin was explained by a model including fasting insulin concentration, sex, body mass index, a nd a body mass index by sex interaction term. Similar results were obt ained if waist circumference replaced body mass index. Conclusions-The strong relation of leptin with obesity is consistent with leptin prod uction being proportional to mass of adipose tissue. The relation with insulin independent of body mass index suggests a possible role for l eptin in insulin resistance or hyperinsulinaemia.