Leptin And Body Fat - Brief Article

Nutrition Research Newsletter,  Jan, 2001  

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Leptin is a protein synthesized and secreted by adipocytes. Its concentration is correlated with percent body fat in humans. Since the identification of the leptin (or ob) gene, many studies have established a role for leptin in regulating body fat. In ongoing genetic studies, researchers have been interested in how the relation between leptin and body fat varies among distinct subgroups as defined by phenotypic variations in obesity or variations in environmental risk factors. Therefore, a recent study in Obesity Research describes how gender-, ethnic-, and age-related differences in serum leptin concentrations vary according to the body composition measures between Hispanic and non-Hispanic white adults.

Seven hundred and sixty-six non-diabetic adults from the San Luis Valley Diabetes Study were included in the study. Serum and plasma leptin concentrations were determined after an overnight fast, and body composition was assessed by dual energy X-ray absorptiometry.

Mean BMI was similar between men and women in the study. Unadjusted fasting leptin concentrations were three to four times higher in women than in men. Fasting serum and plasma leptin levels were correlated with percent body fat. However, women have higher leptin levels than men after adjusting for body fat. Lean body mass was inversely related to leptin concentrations and explained 71% of the gender difference at a given fat mass. Percent body fat explained all of the gender difference in leptin concentrations in both Hispanics and non-Hispanic whites.

The results from this study confirm that percent body fat provides a more accurate description of leptin concentrations across gender, ethnic, and age groups than either fat mass or BMI. Even though it is easy to use BMI for assessing adiposity, these findings recommend that dual energy X-ray absorptiometry should be used when assessing the relationship between leptin and body fat. The authors hypothesized that fat mass adjusted for lean mass would provide the "best" adjusted summary of leptin concentrations. This was based on the assumption that leptin is secreted in proportion to fat mass but that blood volume (represented by lean mass) would also influence blood concentration. However, it was a surprise that there was such a strong independent effect of lean mass in this study. All of this data is important in that the relationship between leptin and body composition may offer further insights into the etiology and pathogenesis of obesity.

Julie A. Marshall, Gary K. Grunwald, William T. Donahoo, Sharon Scarbro, and Susan M. Shetterly, Percent Body Fat and Lean Mass Explain the Gender Difference in Leptin: Analysis and Interpretation of Leptin in Hispanic and Non-Hispanic White Adults, Obesity Research 8(8): 543-552 (November 2000) [Address correspondence to Julie A. Marshall, Ph.D., Department of Preventive Medicine and Biometrics, University of Colorado Health Sciences Center, Box C-245, Denver, CO 80262. E-mail: julie.marshall@uchsc.edu].

COPYRIGHT 2001 Technical Insights, a divison of John Wiley & Sons.
COPYRIGHT 2001 Gale Group