Reductions in whole-body fat mass but not increases in lean mass predict changes in cardiometabolic health indices with exercise training among weight-stable adults

Abstract

We assessed whether body composition changes with 9 months of exercise training predicted changes in cardiometabolic health indices in weight-stable adults. We hypothesized that within ±5% weight change, changes in whole-body fat and lean masses would predict changes in cardiometabolic health indices with exercise training. Using a randomized parallel design, 152 adults (age: 49 ± 8 year; body mass index: 30.0 ± 2.7 kg/m²; mean ± SD) performed resistance exercises 2 d/wk and aerobic exercises 1 d/wk for 9 months. Participants consumed isoenergetic supplements with 0, 10, 20, or 30 g whey protein twice daily and remained weight stable within ±5% of baseline weight. Body weight and composition were measured using dual-energy x-ray absorptiometry pre- and postintervention. Multiple linear regression model was applied for data analyses. Independent of whey protein supplementation, reductions in fat mass predicted increases in high-density lipoprotein cholesterol (unstandardized beta-coefficient [β], −0.03; 95% confidence interval [CI], −0.06 to −0.01; P = .007) and insulin sensitivity index (β, −0.52; 95% CI, −0.95 to −0.09; P = .018) and decreases in waist circumference (β, 0.67; 95% CI, 0.17-1.18; P = .009). In contrast, increases in lean mass did not predict changes in any of the measured cardiometabolic health indices. Health improvements with training that emphasize resistance exercises are typically attributed to increases in lean mass; however, these results underscore reducing body fat to predict cardiometabolic health improvements.

Introduction

Adults with obesity [1] and (or) who engage in sedentary behaviors [2], [3] are more likely to develop dyslipidemia, insulin resistance, glucose intolerance, and hypertension, which increase the relative risks for developing cardiovascular diseases and type 2 diabetes mellitus [4], [5]. Weight loss is one modifiable lifestyle intervention that can improve both cardiometabolic health and body composition. In general, the magnitude of weight change may predict the magnitude of the change in the accompanying health benefits. A moderate weight loss of 5%-10% improves clinical indices of cardiometabolic health while also improving body composition, primarily through reductions in fat mass [6], [7]. Weight change <5% occurring over a prolonged period of time is historically considered within the range of weight stability (±5% body weight change) and is not consistently associated with positive metabolic effects [7]. However, the 2013 report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and The Obesity Society suggested that a sustained weight loss of 3%-5% could reduce blood triglyceride and glucose concentrations, and type 2 diabetes risk [8].

The American College of Sports Medicine recommends regular moderate- to vigorous-intensity aerobic and resistance exercise to reduce cardiovascular disease risk and promote a healthy body weight [9]. Consistent evidence suggests that exercise training without a purposeful reduction in energy intake results in minimal weight loss but promotes positive changes in cardiometabolic health indices [10], [11] and body composition, including reductions in whole-body fat mass and maintained or increased lean mass [10], [12]. The simultaneous changes in cardiometabolic health-related indices and body composition prompt the question of whether body composition changes predict changes in cardiometabolic health indices even in the absence of significant weight loss (weight change within ±5%). Such research findings would provide evidence-based guidance for clinicians and practitioners to educate and encourage people to persist with exercise training with or without significant weight loss to maintain or improve their cardiometabolic health.

Using data from a previously published randomized controlled trial [13], the objectives of this research were to assess the following questions: (1) what are the associations between changes in body mass (±5% body mass change) and changes in cardiometabolic health indices; (2) what are the associations between changes in whole-body fat mass and changes in cardiometabolic health indices; and (3) what are the associations between changes in whole-body lean mass and changes in cardiometabolic health indices in adults who performed exercise training? We hypothesized that within ±5% weight change, changes in whole-body fat and lean masses would predict changes in cardiometabolic health indices with exercise training.