Resistance Training does not Promote Weight Loss Maintenance in Postmenopausal Women

The objective of the study was to determine if a one year long resistance training intervention was more effective in helping postmenopausal women maintain weight loss, after a six month diet-focused weight loss intervention, than nutrition intervention alone. The researchers first hypothesized that the women in the resistance training (RT) intervention group would be able to better maintain their weight and fat mass (FM) losses compared to women in the control group who only received nutrition intervention. Furthermore, the researchers hypothesized that the women in the resistance training intervention group would have a higher resting energy expenditure compared to those in the control group.

Women in both the RT intervention and control groups were provided with nutrition counseling from a registered dietitian once a month. Each subject was given a recommended calorie goal individualized to them based on their daily energy requirements and was counseled on maintaining intake based on their calculated needs. The resistance training intervention was set up as follows: three (non-consecutive) days of resistance training per week for the first six months followed by two days of (non-consecutive) resistance training per week in the last six months. Training intensity was ~70-80% of each subject's one repetition maximum (1RM) and included exercises that targeted every major muscle group. The guidelines set out by the American College of Sports Medicine were used to develop the training program and personal trainers oversaw each session. Body weight, fat mass (FM) and fat free mass (FFM), visceral and subcutaneous adipose tissue (VAT/SAT), resting energy expenditure (EE), and total daily energy expenditure (EE) were all measured before and after the start of the one year intervention.

Post-intervention data showed that there was no significant difference in weight maintenance between the control and intervention groups- body weight and fat mass regain were similar in both groups. The intervention group did lose more subcutaneous (SAT fat) compared to the control group. Resting energy expenditure was not affected by 1 year of resistance training as it was expected to. Resting energy expenditure was the same after the intervention as it was after the six month weight loss time period. These findings suggest that weight maintenance is not achieved by one specific intervention, but can be achieved by either diet, resistance training- or a combination of both in postmenopausal women. The results also call for more research into the effects of increased intensity/duration/frequency of strength training on weight maintenance.

Two strengths of this study are its intensive inclusion requirements for participating and its techniques for measuring body composition and energy requirements. There are 11 inclusion criteria that subjects had to meet to enter the trial, reducing the chance that factors that were unaccounted for affected the results. Furthermore, all of the measurements taken were done so by gold-standard practices (FM and FFM were measured using a DXA scanner, VAT and SAT were measured using with a CT scan, REE was measured using indirect calorimetry, and daily EE was measured using doubly labeled water). Two weaknesses of this study are its moderate compliance and small sample size. Adherence to the resistance training program was mediocre at 64%, which could have affected outcomes. Additionally, the sample size was only 54 so the data could be misrepresentative of the population.

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