Body mass does not reflect the body composition changes in response to similar physical training in young women and men

Abstract

Introduction: U.S. Army Basic Combat Training (BCT) prepares new recruits to meet soldier physical demands. It also serves as a model of physical changes in healthy young nonobese women and men during an intensive 10-week training program without diet restriction. In this prospective observational study, we quantified the changes in lean mass and body fat induced by BCT in a large sample of men and women undergoing the same physical training program.

Methods: Young women (n = 573) and men (n = 1071) meeting Army health and fitness recruitment standards volunteered to provide DXA-derived body composition data at the beginning and end of BCT.

Results: During BCT, there was no change in body mass in women and a 1.7-kg loss in men. Relative body fat (%BF) declined by an average of 4.0 ± 2.4 and 3.4 ± 2.8 percentage points (±SD) for women and men, respectively. The greatest predictor of change in %BF during BCT for both sexes was %BF at the beginning of training. Women and men gained an average 2.7 ± 1.6 kg and 1.7 ± 2.0 kg of lean mass during BCT.

Conclusions: Army BCT produced significant effects on body composition despite minimal changes in total body mass. These findings demonstrate the ability of a 10-week sex-integrated physical training program to positively alter body composition profiles of young adults.