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

## TL;DR

This study found that higher insulin sensitivity helps retain lean mass during diet-only weight loss, but adding exercise negates this benefit.

## Contribution

The study reveals that baseline insulin sensitivity predicts lean mass retention only in diet-only weight loss, not when combined with exercise.

## Key findings

- Higher baseline insulin sensitivity was linked to less lean mass loss in diet-only groups.
- Exercise (aerobic or resistance) eliminated the protective effect of insulin sensitivity on lean mass.
- Including exercise in weight loss interventions is crucial for preserving lean mass.

## Abstract

This study aimed to investigate the association between baseline insulin sensitivity (SI) 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 SI using an intravenous glucose tolerance test. Multiple linear regression was used to determine if baseline SI was predictive of changes in total LM and ALM.

There were significant group‐SI 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 SI was associated with less LM loss only in women who did not exercise.

Higher baseline SI 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.

Trial Registration: ClinicalTrials.gov identifier: NCT00067873