Aims: We investigated whether low subcutaneous thigh fat is an independent risk factor for unfavourable glucose and lipid levels, and whether these associations differ between sexes, and between white and black adults. Our secondary aim was to investigate which body composition characteristics (lean tissue, fat tissue) are reflected by anthropometric measures (waist and thigh circumference).
Methods: Anthropometric measurements and computed tomography of the abdomen and of the thigh were performed for all participants of the Health, Aging and Body Composition Study, who were aged 70-79 years. Fasting glucose, triglycerides and HDL-cholesterol, and 2-h postload glucose were determined.
Results: After excluding those already diagnosed with diabetes or dyslipidaemia, we analysed data from 2,106 participants. After adjustment for abdominal subcutaneous and visceral fat, and intermuscular thigh fat, larger thigh subcutaneous fat area was statistically significantly associated with lower ln-transformed triglycerides [standardised beta (95% CI) -0.12 (-0.20 to -0.04) in men and -0.13 (-0.21 to -0.05) in women] and higher ln-HDL-cholesterol [0.10 (0.02 to 0.19) and 0.09 (0.01 to 0.18), respectively]. The associations with lower glucose levels were strong in men [-0.11 (-0.20 to -0.02) for fasting and -0.14 (-0.23 to -0.05) for postload glucose], but not statistically significant in women [-0.02 (-0.10 to 0.07) and -0.04 (-0.13 to 0.05), respectively]. There were no differences in the associations between white and black persons. Waist circumference was more strongly associated with abdominal subcutaneous fat, and this association became stronger with increasing BMI, whereas the association with visceral fat became weaker. Thigh circumference was equally dependent on thigh fat and thigh muscle in men, whereas in women the fat component was the main contributor.
Conclusion: Larger subcutaneous thigh fat is independently associated with more favourable glucose (in men) and lipid levels (in both sexes) after accounting for abdominal fat depots, which are associated with unfavourable glucose and lipid levels. Anthropometric measures reflect different fat depots at different levels of BMI at the abdomen, and reflect both fat and lean tissue at the thigh. These results emphasise the importance of accurate measures of regional body composition when investigating potential health risks.