Objective: In the current obesity epidemic, the ability to remain lean is beginning to be uncommon. Therefore, it was considered of interest to characterize such subjects.
Research Methods and Procedures: From a population of premenopausal women (n = 270), all 40 years of age, those with a similar body mass index (BMI) as women at the age of 21 years, born the same year (BMI = 21.1 kg/m2) were selected among nonsmokers and compared with the remaining nonsmoking women.
Results: Lean women showed, as expected, low waist-to-hip circumference ratio and abdominal sagittal diameter as well as absence of other disease risk factors. Compared with the remaining women, 17β-estradiol was high and androgens were low, whereas insulin-like growth factor I and thyroid hormones showed no differences. Dihydroepiandrosterone sulfate was lower, whereas cortisol, measured in saliva repeatedly over a day, and adrenocorticotropin hormone were not different. Results from questionnaires indicated higher education and socioeconomic status, frequent sports activities, and better psychosocial adaptation and psychological health. A tetranucleotide repeat polymorphism in the fifth intron of the aromatase P450 gene was longer among the lean (187 base pairs) than the rest of the women. Women with opposite phylogenetic characteristic have a short microsatellite (168 base pairs) in this gene locus.
Discussion: Lean, nonsmoking women enjoy an excellent health in not only anthropometric and metabolic factors, but also in neuroendocrine, endocrine, and psychological variables. The endocrine measurements suggest a well-functioning aromatase, which in turn might have a genetic background, contributing to health. The aromatase gene might be important for regulation of body fat mass.