The Role of Insulin Sensitivity in Lean Mass Changes During Weight Loss With or Without Exercise

This study aimed to investigate the association between baseline insulin sensitivity (S_I) and changes in total lean mass (LM) and appendicular LM (ALM) during a diet-induced weight loss program with or without exercise.

We conducted a secondary data analysis from a controlled weight loss study in premenopausal women with overweight aged 21-41. Women were randomized into three groups: diet-only, diet plus aerobic exercise, or diet plus resistance exercise. Body composition was assessed using dual-absorptiometry X-ray and S_I using an intravenous glucose tolerance test. Multiple linear regression was used to determine if baseline S_I was predictive of changes in total LM and ALM.

There were significant group-S_I interactions on changes in total LM (β = 0.474, p = 0.003, adjusted r ² = 0.371) and ALM (β = 0 0.462, p = 0.009, adjusted r ² = 0.231) after adjusting for covariates, indicating that greater baseline S_I was associated with less LM loss only in women who did not exercise.

Higher baseline S_I is associated with greater retention of LM when weight loss is induced with diet alone, but not when exercise (aerobic or resistance) is included. This reinforces the importance of including exercise in all weight loss interventions.

ClinicalTrials.gov identifier: NCT00067873.