Sex differences in body composition and association with cardiometabolic risk

Abstract

Background: Body composition differs between men and women, with women having proportionally more fat mass and men more muscle mass. Although men and women are both susceptible to obesity, health consequences differ between the sexes. The purpose of our study was to assess sex differences in body composition using anatomic and functional imaging techniques, and its relationship to cardiometabolic risk markers in subjects with overweight/obesity.

Methods: After written informed consent, we prospectively recruited 208 subjects with overweight/obesity who were otherwise healthy (94 men, 114 women, age 37 ± 10 years, BMI 35 ± 6 kg/m²). Subjects underwent dual-energy X-ray absorptiometry (DXA) and computed tomography (CT) for fat and muscle mass, proton MR spectroscopy (1H-MRS) for intrahepatic (IHL) and intramyocellular lipids (IMCL), an oral glucose tolerance test, serum insulin, lipids, and inflammatory markers. Men and women were compared by Wilcoxon signed rank test. Linear correlation and multivariate analyses between body composition and cardiometabolic risk markers were performed.

Results: Women and men were of similar mean age and BMI (p ≥ 0.2). Women had higher %fat mass, extremity fat, and lower lean mass compared to men (p ≤ 0.0005). However, men had higher visceral adipose tissue (VAT) and IMCL and higher age-and BMI-adjusted IHL (p < 0.05). At similar age and BMI, men had a more detrimental cardiometabolic risk profile compared to women (p < 0.01). However, VAT in women, and IMCL in men, were more strongly associated with cardiometabolic risk markers, while more lower extremity fat was associated with a more favorable cardiometabolic profile in women compared to men (p ≤ 0.03).

Conclusions: Although the male pattern of fat distribution is associated with a more detrimental cardiometabolic risk profile compared to women of similar age and BMI, VAT is more strongly associated with cardiometabolic risk markers in women, while IMCL are more detrimental in men. Lower extremity fat is relatively protective, in women more than in men. This suggests that detailed anatomic and functional imaging, rather than BMI, provides a more complete understanding of metabolic risk associated with sex differences in fat distribution.

Keywords: Body composition; Computed tomography; Magnetic resonance spectroscopy; Metabolic syndrome; Obesity; Sex characteristics.

Fig. 1

CT and 1H-MRS for body composition in a 35-year-old man with obesity (BMI 37 kg/m²). Fasting LDL cholesterol 118 mg/dL, HDL cholesterol 39 mg/dL, triglycerides 74 mg/dL, glucose 84 mg/dL, insulin 19 μU/mL, HOMA-IR 3.3, 2-h glucose from oral glucose tolerance test 144 mg/dL. a CT of the abdomen at the level of L4 for quantification of visceral adipose tissue (194 cm²) (white diamond) and subcutaneous adipose tissue (open diamond) (458 cm²). b CT of the mid-thigh for quantification of subcutaneous adipose tissue (open diamond) (123 cm²) and muscle (black diamond) (207 cm²). c 1H-MR spectrum of the right hepatic lobe for intrahepatic lipid quantification showing lipid (1.3 ppm) and unsuppressed water (4.7 ppm) resonances. Lipid to water ratio was 0.8. d 1H-MR spectrum of soleus muscle for intramyocellular lipid quantification showing intramyocellular lipid methylene protons (-CH2) at 1.3 ppm (IMCL), extramyocellular lipid methylene protons (-CH2) at 1.5 ppm (EMCL), residual water peak at 4.7 ppm, and creatine (-CH2) resonance at 3.0 ppm. IMCL/unsuppressed water ratio was 0.06

Fig. 2

CT and 1H-MRS for body composition in a 35-year-old woman with obesity (BMI 38 kg/m²). Despite similar age and BMI, the woman had lower visceral adipose tissue and thigh muscle cross sectional area (CSA), lower intrahepatic and intramyocellular lipids and higher thigh subcutaneous adipose tissue compared to the man in Fig. 1, and this was associated with a more favorable cardiometabolic risk profile compared to the man. Fasting LDL cholesterol 104 mg/dL, HDL cholesterol 59 mg/dL, triglycerides 50 mg/dL, glucose 72 mg/dL, insulin 3 μU/mL, HOMA-IR 0.48, 2-h glucose from oral glucose tolerance test 84 mg/dL. a CT of the abdomen at the level of L4 for quantification of visceral adipose tissue (30 cm²) and subcutaneous adipose tissue (450 cm²). b CT of the mid-thigh for quantification of subcutaneous adipose tissue (208 cm²) and muscle (110 cm²). c 1H-MR spectrum of the right hepatic lobe for intrahepatic lipid quantification showing lipid (1.3 ppm) and unsuppressed water (4.7 ppm) resonances. Lipid to water ratio was 0.01. For purposes of visual comparison, the amplitude of unsuppressed water in Figs. 1c and 2c were scaled identically. d 1H-MR spectrum of soleus muscle for intramyocellular lipid quantification showing intramyocellular lipid methylene protons (-CH2) at 1.3 ppm (IMCL), extramyocellular lipid methylene protons (-CH2) at 1.5 ppm (EMCL), residual water peak at 4.7 ppm, and creatine (-CH2) resonance at 3.0 ppm. IMCL/unsuppressed water ratio was 0.02. For purposes of visual comparison, the amplitude of total creatine peaks in Figs. 1d and 2d were scaled identically