Effect of loss of regional fat assessed by DXA on insulin resistance and dyslipidaemia in obese men

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/m(2)) 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%; Delta trunk and Delta 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 (R-2 = 0.60, p = 0.013, R-2 = 0.37, p = 0.012, respectively) and in HOMA-IR by trunk FM (R-2 = 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.