Stronger effect of resistance training when combined with protein supplementation

A meta-analysis of Randomized Controlled Trials among overweight older people

Resistance exercise combined with protein supplementation and a varied diet is known to have a positive effect on muscle mass and strength in the elderly. However, the effect of body weight on the augmentation of muscular and functional performance in response to protein supplementation in older people undergoing resistance type exercise remains unclear. Therefore, Liao and colleagues (2017) performed a meta-analysis to examine the effect of resistance exercise combined with protein supplementation on body composition and physical function in the elderly with a BMI ≥ 25 kg/m2.

Summary | Resistance training combined with protein supplementation may have stronger effects on muscle volume and physical function of overweight and obese elderly than resistance training alone.

 

With aging changes in body composition result in the percentage of fat mass increasing and fat free mass decreasing gradually. This is a natural aging process, which can be slowed down by a healthy lifestyle, such as  physical activity and varied diet with sufficient amounts of protein. Liao et al (2017) performed a meta-analysis of Randomized Controlled Trials to examine the effect of resistance exercise combined with protein supplementation on the physical function and body composition of elderly people with a BMI ≥ 25 kg/m2. (1)

Study characteristics

Stronger effect of resistance training when combined with protein supplementationThe researchers conducted an extensive search of the literature and included 17 Randomized Controlled Trials (RCT) in the meta-analysis which met all the selection criteria described under the Methods section of the original publication of Liao et al (2017). The RCTs were published between 2001 and 2016 and include a total of 892 participants with a mean age of 73.4 ± 7.9 years, a BMI (kg/m2) of 29.7 ± 5.4 and a body fat percentage of 35.8% ± 10.2%. During the RCTs about half of the participants (n=459) received a protein supplement along with resistance training (treatment group) and the other half of the participants (n=433) received a placebo supplement during the resistance training (placebo group).

Protein supplementation

Participants in the treatment group received a protein supplement in addition to their habitual diet. The amount, type of protein and protein source differed between the 17 RCTs. In 15 RCTs the amount of protein supplementation ranged from 10 to 35 gram per day. In the remaining 2 trials the amount of protein supplementation was quantified according to the body weight of the participants, with protein supplementation of 0.3 gram/kilogram per day. In the 17 RCTs various types of protein supplementation were given to the participants: whey protein, leucine, casein, milk protein and the leucine metabolite β-hydroxy β-methyl butyrate. In 11 of the 17 RCTs the participants received a protein supplement every day; in the other 6 RCTs the participants received a protein supplement on training days only.

Resistance training

The duration of the resistance training differed between the 17 RCTs. The 6 longest RCTs used an intervention period of 24 weeks or longer (consisting of 48-72 sessions), the medium intervention, 8 RCTs, used a training period of 12-24 weeks (consisting of 24-48 sessions) and the 3 shortest RCTs in the meta-analysis used an intervention period of less than 12 weeks (consisting of 12-56 sessions). In 13 of the 17 RCTs the resistance training was focused on the whole body, whereas in the other 4 RCTs, training was focused on the lower extremities. The researchers Liao et al (2017) provided an overview of all study characteristics, including the details of the schedule of resistance training in a supplemental table in the original publication.

Results

Body composition

Participants in the resistance training + protein supplement group had a significantly greater improvement in lean body mass than the participants who only received resistance training (0.58, 95% CI: 0.32-0.84). A longer intervention period of 24 weeks or more was more effective (0.66, 95% CI: 0.35-0.97) than a shorter training period. Men in the resistance training + protein supplementation group had a significantly greater improvement in lean body mass than women (0.95, 95% CI: 0.55-1.35).

A subgroup analysis of participants having a BMI ≥30 kg/ m2 showed that resistance training + protein supplementation improved lean body mass (0.53, 95% CI: 0.19-0.87) as well as in participants with a BMI <30 kg kg/ m(0.63, 95% CI: 0.28-0.98).

Muscle function

Participants in the resistance training + protein supplement group had a significantly greater improvement in overall muscle volume (1.23, 95% CI: 0.50-1.96) than the participants who only received resistance training. There was also a greater increase in leg strength among the resistance training + protein supplementation group (0.69, 95% CI: 0.39-0.98). This effect was significantly greater in men (0.87, 95% CI: 0.43-1.31) than women. A training period of 12-24 weeks was significantly more effective than a shorter training period of less than 12 weeks. There was no significant increase in favor of protein supplementation in respect of handgrip strength or upper body strength.

A subgroup analysis of participants with a BMI <30 kg/ m2 showed that resistance training + protein supplementation significantly increased muscle volume (1.42, 95% CI: 0.43-2.41) in favor of protein supplementation, whereas participants with higher BMI values didn’t.

Conclusion

Liao et al (2017) conclude that resistance training combined with protein supplementation has a significant improving effect on body composition, muscle volume and leg strength in older overweight and obese elderly, compared with resistance training alone without protein supplementation.

References

Liao et al (2017). Effects of protein supplementation combined with resistance exercise on body composition and physical function in older adults: a systematic review and meta-analysis. The American Journal of Clinical Nutrition, 2017; 106: 1078-1091.