Effect of Endogenous Hormone Levels on Basal Metabolic Rate in Men With Obesity

Objective: Basal metabolic rate (BMR) is an important factor in weight management and is influenced by fat-free mass (FFM), fat mass (FM) and age. Current knowledge of the influence of hormonal levels on BMR is based on studies with small populations, studies that investigate exogenous administration and studies frequently lacking correction for body composition.

Design: Cross-sectional study.

Patients: All men (n = 457) who were referred to our centre for a metabolic work-up were eligible for inclusion. Median age was 47 (18-78) years and the vast majority had obesity (BMI ≥ 30 kg/m², 90.9%).

Measurements: All men had a measurement of BMR, body composition and measurement of testosterone, sex hormone binding globulin (SHBG), dehydroepiandrosterone sulphate (DHEAS), insulin-like growth factor 1 (IGF-1), thyroid-stimulating hormone (TSH) and free thyroxine (fT4). Men with low, normal and/or high levels of each of these hormones were compared. The association between hormone levels and BMR was assessed through linear regression models. All analyses were controlled for FFM, FM and age.

Results: In men with obesity, testosterone (total or free) was not associated with BMR. Linear regression analysis showed that DHEAS was positively associated with BMR in a sample of men with obesity and normal endogenous DHEAS levels, with the following equation: BMR (adjusted R² = 0.72): (BMR [kcal/d] = 513.402 + 18.940 × FFM [kg] + 9.507 × FM [kg] - 3.362 × age [years] + 0.307 × DHEAS [µg/dL]) (p < 0.01). TSH, fT4 and IGF-1 were not associated with BMR.

Conclusion: In men with obesity, endogenous DHEAS is positively associated with BMR. Testosterone, TSH, fT4 and IGF-1 were not associated with BMR in men with obesity. Since we examined the specific population of men with obesity and only examined endogenous hormone levels, no extrapolation of results to other populations or the overall population can be made.