Weight training increases fat-free mass and strength in untrained young women

J Am Diet Assoc. 1998 Apr;98(4):414-8. doi: 10.1016/S0002-8223(98)00094-7.


Objective: To examine the effects of a weight training program on the resting metabolic rate, fat-free mass, strength, and dietary intake of untrained young women.

Design: A 12-week weight training program was completed by 20 previously untrained women aged 19 through 44 years.

Subjects: Twenty-three study subjects and 14 control subjects were recruited on a volunteer basis. Twenty study subjects and 10 control subjects completed the study.

Interventions: Study subjects participated in a 12-week moderate-intensity, progressive resistance weight training program consisting of 2 supervised sessions per week with 6 types of lifting exercises per session. Resting metabolic rate, fat-free mass, strength, and dietary intake were measured before and immediately after the study.

Statistical analyses: Repeated measures analysis of variance and t tests (unequal variance and paired) were used to determine interaction effects and differences within and between groups.

Results: The study group increased their fat-free mass (mean+/-standard deviation) from 44.2+/-5.4 kg to 46.2+/-6.0 kg (P<.001). Elbow flexion, elbow extension, and knee flexion strength all increased from 28.9+/-5.3 to 34.5+/-3.8, 16.9+/-4.9 to 22.1+/-5.3, and 39.5+/-8.6 to 48.6+/-7.3 ft-lb, respectively (P<.001). Percent body fat decreased from 29.8+/-2.8 to 27.2+/-2.6 (P<.001) without a significant change in body weight. Resting metabolic rate did not change significantly (P>.05).

Application: A moderate-intensity weight training program increased strength and fat-free mass and decreased body fat in normal-weight young women. Favorable changes in body composition were obtained without restricting food intake. The increase in fat-free mass did not increase resting metabolic rate significantly.

MeSH terms

  • Adult
  • Body Composition / physiology*
  • Calorimetry, Indirect
  • Eating / physiology
  • Energy Metabolism
  • Female
  • Humans
  • Muscle, Skeletal / physiology*
  • Physical Fitness / physiology*
  • Skinfold Thickness
  • Weight Lifting / physiology*