Weight reduction does not induce an undesirable decrease in muscle mass, muscle strength, or physical performance in men with obesity: a pilot study.

Bokun Kim,Rina So,Xiaoguang Zhao,Takehiko Tsujimoto,Sechang Oh,Kiyoji Tanaka

doi:10.20463/jenb.2017.0029

Abstract

[Purpose]To date, there have been no reports on whether weight reduction causes decreases in muscle mass, muscle strength, or physical performance that could lead to health problems. Thus, in this pilot study, we investigated the appropriateness of the changes in muscle mass, muscle strength and physical performance after weight reduction. [Methods]Obese men who completed a weight reduction program to decrease and maintain a body mass index (BMI) of less than 25 kg/m2 for one year were recruited for the study. One year after the completion of a weight reduction program, the participants’ muscle mass, muscle strength, and physical performance were compared with those in a reference group composed of individuals whose BMI was less than 25 kg/m2. Whole-body scanning was performed using dual-energy X-ray absorptiometry to analyze muscle mass. Handgrip strength and knee extensor strength were measured to evaluate arm and leg muscle strength, respectively. For physical performance, a jump test was employed. [Results]The results showed that the biceps, triceps, subscapular, and suprailiac areas of professional fashion models were significantly thinner than those of women in general (p<.001), and that their waist size was also significantly smaller (p<.001). However, hip circumference showed no significant difference. Body mass index, waist-to-hip ratio, and body fat (%) in professional fashion models were significantly lower than those in women in general (p<.001), while the body density in professional fashion models was significantly greater (p<0.001). [Conclusion]Weight reduction participants showed an average reduction in body weight of -16.47%. Normalized arm muscle mass and handgrip strength were significantly greater in the weight reduction group than in the reference group; however, no significant differences were detected between the two groups with respect to the other variables. After one year, there were no significant differences between the two groups.

Highlights

Obesity causes a broad range of chronic conditions, including heart disease, hypertension, and diabetes 1, and contributes to musculoskeletal conditions, such as osteoarthritis, epicondylitis, tendinitis, and back pain [2,3,4]
No significant differences were observed between the two groups with regard to any of the variables. This pilot study aimed to investigate whether weight reduction significantly decreases muscle mass, muscle strength, or physical performance to cause health problems, and the primary findings of this study were as follows: First, the arm muscle mass (AMM) in the weight reduction group was significantly less than that in the reference group after completion of the weight reduction program
There were no significant differences between the two groups with respect to the absolute or relative values for muscle strength and physical performance, except in the handgrip strength per AMM, which was significantly higher in the weight reduction group than in the reference group

Summary

Introduction

Obesity causes a broad range of chronic conditions, including heart disease, hypertension, and diabetes 1, and contributes to musculoskeletal conditions, such as osteoarthritis, epicondylitis, tendinitis, and back pain [2,3,4]. The incidence of osteoarthritis increases by 36% for every 5-kg increase in body weight 5. Weight reduction is beneficial in preventing or ameliorating musculoskeletal conditions. The effect of weight reduction on musculoskeletal conditions is clear, weight reduction decreases both fat mass and muscle mass 8. A rapid decrease in muscle mass caused by substantial weight reduction might decrease muscle strength, which is likely to decrease physical performance [8,9,10,11]. Low muscle mass and strength are linked to the incidence of musculoskeletal conditions [10, 12,13,14]. The concomitant loss of muscle mass and strength induced by weight reduction is, an important concern

Methods

Results

Discussion

Conclusion