INSULIN AND LEPTIN CONCENTRATIONS IN OBESE HUMANS DURING LONG-TERM WEIGHT-LOSS

Background: Leptin is likely to be involved in the homeostasis of body weight. Insulin is suggested to regulate both short-term and long-ter m circulating leptin levels. The present study aims to assess the rela tion between insulin and leptin levels in obese humans. Methods: Some 53 obese subjects (body mass index 35.1 +/- 3.9 kg m(-2) (mean +/- SD) ) were prescribed a hypocaloric diet and randomized to either a placeb o or the intestinal lipase inhibitor orlistat for 2 years, Serum lepti n and insulin levels were determined repeatedly during these 2 years ( 5 times in the fasting condition and twice after an oral glucose load) . Results: Leptin concentrations appeared to be regulated at a specifi c level for each individual throughout the weight-loss period. The BMT explained 39.7% of the total variance in leptin levels, the body-fat distribution 17.2%, individual characteristics 30.3%, and the fasting serum insulin concentration 1.0%. After a mean weight loss of 7.7 +/- 4.9 kg, the time-integrated insulin response to an oral glucose load w as significantly lower but the leptin response remained unchanged. Con clusions: The BMI is the main determinant of the circulating leptin co ncentration in obese humans. Individual characteristics seem to determ ine the leptin level, given the BMI. In a short-term and long-term obs ervational study in obese humans, changes of insulin levels do not app ear to be correlated to changes in leptin levels. (C) 1997 Elsevier Sc ience B.V.