Resistance training preserves fat-free mass without impacting changes in protein metabolism after weight loss in older women

Abstract

This study assessed the effects of resistance training (RT) on energy restriction-induced changes in body composition, protein metabolism, and the fractional synthesis rate of mixed muscle proteins (FSRm) in postmenopausal, overweight women. Sixteen women (age 68 +/- 1 years, BMI 29 +/- 1 kg/m(2), mean +/- s.e.m.) completed a 16-week controlled diet study. Each woman consumed 1.0 g protein/kg/day. At baseline (weeks B1-B3) and poststudy (weeks RT12-RT13), energy intake matched each subject's need and during weeks RT1-RT11 was hypoenergetic by 2,092 kJ/day (500 kcal/day). From weeks RT1 to RT13, eight women performed RT 3 day/week (RT group) and eight women remained sedentary (SED group). RT did not influence the energy restriction-induced decrease in body mass (SED -5.8 +/- 0.6 kg; RT -5.0 +/- 0.2 kg) and fat mass (SED -4.1 +/- 0.9 kg; RT -4.7 +/- 0.5 kg). Fat free mass (FFM) and total body water decreased in SED (-1.6 +/- 0.4 and -2.1 +/- 0.5 kg) and were unchanged in RT (-0.3 +/- 0.4 and -0.4 +/- 0.7 kg) (group-by-time, P < or = 0.05 and P = 0.07, respectively). Protein-mineral mass did not change in either group (SED 0.4 +/- 0.2 kg; RT 0.1 +/- 0.4 kg). Nitrogen balance, positive at baseline (2.2 +/- 0.3 g N/day), was unchanged poststudy. After body mass loss, postabsorptive (PA) and postprandial (PP) leucine turnover, synthesis, and breakdown decreased. Leucine oxidation and balance were not changed. PA and total (PA + PP) FSRm in the vastus lateralis were higher after weight loss. RT did not influence these protein metabolism responses. In summary, RT helps older women preserve FFM during body mass loss. The comparable whole-body nitrogen retentions, leucine kinetics, and FSRm between groups are consistent with the lack of differential protein-mineral mass change.

Figure 1

Experimental design and approximate study schedule of the 16-week protocol that included a 3-week baseline period (B1–B3) and an 11-week period of intervention (dietary energy restriction with (n = 8) or without (n = 8) resistance training (RT1–RT11), and a 2-week postintervention period (RT12–RT13)).

Figure 2

Protocol for L-[1-¹³C]leucine and L-[ring-²H₅]phenylalanine infusion used to measure whole-body protein turnover and mixed muscle fractional synthesis rate, respectively. X indicates the time that a beverage was provided, resting energy expenditure (REE) measurement completed, blood draw and breath samples were taken, and muscle biopsy procedure performed. ↓ indicates the administration of the priming doses of NaH¹³CO₃, L-[1-¹³C]leucine and L-[ring-²H₅]phenylalanine. Beverages contained 8.33% of each subject’s estimated daily energy and dietary protein needs.

Figure 3

Body mass and composition changes after an 11-week period of energy restriction in overweight postmenopausal women who were sedentary (n = 8) or resistance training (n = 8). FFM, fat-free mass; PMM, protein–mineral mass; TBW, total body water. Differential response between the sedentary and resistance training groups, group-by-time interaction, *P ≤ 0.05; ^†P = 0.07.

Figure 4

Changes in the rates of whole-body leucine turnover (Flux), synthesis (Syn), and oxidation (Ox) after an 11-week period of energy restriction–induced body mass loss in overweight postmenopausal women who were sedentary (n = 8) or who were resistance training (n = 8). The rates were measured during an 8-h primed, constant infusion of L-[1-¹³C]leucine while the subjects were in postabsorptive and postprandial states, and the changes calculated as postintervention − baseline. Values are mean ± s.e.m. *Significant main effect of time, P ≤ 0.05.

Figure 5

Fractional synthesis rate of mixed muscle proteins (FSRm) in the vastus lateralis before (baseline) and after (resistance training week 12, RT12) an 11-week period of energy restriction–induced body mass loss in overweight postmenopausal women who were sedentary (n = 8) or resistance training (n = 8). The FSRm was measured during an 8-h primed, constant infusion of L-[ring-²H₅]phenylalanine while the subjects were in postabsorptive and postprandial states. Total FSRm was measured from the incorporation of isotope during the postabsorptive and postprandial periods combined. Values are mean ± s.e.m. *Significant main effect of metabolic state (postabsorptive vs. postprandial) at baseline, P ≤ 0.05. ^†Significant main effect of time (baseline vs. week R12), P ≤ 0.05.