Objective: To investigate the impact of reduction in total fat mass (FM) and regional FMs on indices of insulin resistance and dyslipidaemia in obese men (BMI > 30 kg/m²) after a 1-year weight loss (WL), and secondly, to examine the potential predictive effect of baseline insulin resistance on reduction in total and regional FMs.
Material and methods: In nine men with WL > 4 kg, body composition by DXA (dual X-ray absorptiometry) and indices of insulin resistance were assessed: fasting insulin, C-Peptide and HOMA-IR. Insulin sensitivity (QUICKI) and serum lipids were also assessed.
Results: Mean WL was 10.8%; Δ trunk and Δ leg FM were reduced by 30.1% and 21.3%, respectively, increasing leg/trunk FM ratio by 13.2%. Improvement in HOMA-IR was 63.1%, insulin 59.1%, and in QUICKI 17.4%. Loss of total FM, trunk FM, and increase in leg/trunk FM ratio were correlated with improvement in HOMA-IR (p < 0.001-0.05). Linear regression analysis of ln-transformed improvements in HOMA-IR was non-significantly related with losses of trunk FM and increases in leg/trunk FM ratio (p = 0.06). Multivariate analysis suggested improvements in fasting insulin and C-Peptide could be explained by leg/trunk FM ratio (R² = 0.60, p = 0.013, R² = 0.37, p = 0.012, respectively) and in HOMA-IR by trunk FM (R² = 0.42, p = 0.06). The loss of FM and change in FM distribution had no effect on serum lipids.
Conclusion: Both loss of trunk FM and increase in leg/trunk FM ratio assessed by DXA contribute to the improvement in insulin resistance.