Exercise and Protein Effects on Strength and Function With Weight Loss in Older Women

Ellen M. Evans; Chad R. Straight; Rachelle A. Reed; Alison C. Berg; David A. Rowe; Mary Ann Johnson

Disclosures

Med Sci Sports Exerc. 2021;53(1):183-191. 

In This Article

Abstract and Introduction

Abstract

Obesity negatively affects lower extremity physical function (LEPF) in older adults. Exercise and a higher protein diet are both known to positively and independently affect body composition, muscle strength, and LEPF during weight loss; however, their potential interactive effects have not been well characterized in older women.

Purpose: The aim of this study was to determine the relative efficacy of a higher protein diet with or without exercise to improve body composition, muscle strength, and LEPF in older inactive overweight/obese women after weight loss.

Methods: Postmenopausal women (body mass index = 31.1 ± 5.1 kg·m−2, 69.2 ± 3.6 yr) completed a 6-month weight loss program after randomization to three groups (n = 72 randomized; 15% dropout): 1) higher protein diet (PRO, ~30% energy from protein; n = 20), 2) PRO plus exercise (PRO + EX; n = 19), or 3) a conventional protein control diet plus EX (CON + EX, ~18% energy from protein; n = 22). EX was supervised, multicomponent (aerobic, muscle strengthening, balance, and flexibility), and three sessions per week. Body composition was measured via dual-energy x-ray absorptiometry, leg strength by isokinetic dynamometry, and LEPF via 6-min walk, 8-ft up and go, and 30-s chair stand tests.

Results: Changes in weight (−7.5 ± 4.1 kg; −9.2% ± 4.8%), fat mass, and leg lean mass did not differ among groups (all P > 0.50). Despite weight loss, muscle strength improved in the exercise groups (PRO + EX and CON + EX) but it declined in the PRO group (P = 0.008). For all LEPF measures, the PRO group had attenuated improvements compared with both PRO + EX and CON + EX (all P < 0.01).

Conclusion: Exercise during weight loss is critical to preserve strength and enhance LEPF; however, a higher protein diet does not appear to influence body composition, muscle strength, or LEPF changes when combined with multicomponent exercise.

Introduction

Obesity in older adults is of great concern as it is associated with reductions in physical function and an increased risk for physical disability,[1] especially in older women.[2,3] It has been established that weight loss and exercise/physical activity interventions are effective behavioral strategies for attenuating functional decline and reducing risk for disability in older adults.[3] However, weight loss in older adults typically causes concurrent reductions in lean mass and strength, thereby exacerbating the risk for sarcopenia and dynapenia.[1] The inclusion of exercise in a calorically restricted weight loss regimen attenuates lean mass and strength loss and is advocated as a critical component of weight loss programs for older adults.[1] Regarding the latter, Villareal and colleagues[4] were one of the first to report that calorically restricted weight loss and exercise combined resulted in greater improvements in physical function compared with weight loss or exercise alone in older adults.

In addition to exercise training, emerging literature also suggests that increased dietary protein is another strategy to enhance favorable body composition changes under weight loss conditions, specifically preservation of muscle mass[5] and greater reductions in fat mass.[6] However, the effect of protein intake on body composition changes, and relatedly strength and physical function, in response to a calorically restricted weight loss regimen remains an active area of investigation as the current literature focused on older adults is equivocal.[7–11] Further, the literature is lacking controlled trials balanced in internal and external validity that (a) explore the potential additive benefits of multicomponent exercise training (i.e., aerobic/endurance, resistance training, functional/balance) and dietary protein; (b) are of a longer duration (>3 months); (c) have outcome measures of body composition, strength, and physical function; and (d) use readily available food (i.e., dietary food not supplied; minimal/no use of protein powders/supplements) in older women known to be at higher risk for obesity and physical disability compared with their male counterparts.[3]

Multicomponent exercise training and dietary protein may have complicated, interactive implications for changes in lower extremity physical function (LEPF) in older adults because of differential effects on weight change, individual body composition components (i.e., fat and lean mass), and muscle strength. Specifically, conceptually framed, reducing the load to be moved (i.e., weight and fat mass), and maintaining or enhancing the ability to move the load (i.e., preserving high-quality muscle mass) theoretically should confer the greatest improvements in LEPF. The literature in this area remains equivocal, although promising, and reviews call for additional clinical trial research before best practice guidelines can be established.[1,11,12]

In this context, the aim of this study was to determine the relative efficacy of a higher protein diet with or without exercise to improve body composition, muscle strength, and LEPF in older inactive overweight/obese women enrolled in a 6-month weight loss program. We hypothesized that although all treatments would confer favorable effects on weight status, body composition, and LEPF, the higher protein diet combined with exercise group would experience the greatest benefit in all outcomes of interest, especially LEPF, compared with the conventional protein control diet with exercise or protein diet alone groups.

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