This is a plain English summary of an original research article
Combining resistance training with aerobic exercise increased physical function in older, obese adults who were following a weight loss programme. Functional improvements, such as the speed to stand from a chair or to climb stairs, were greater with combination training (21%) than with either type of exercise performed alone (14%).
This randomised controlled trial assigned 160 obese adults in the USA (aged over 65, mostly educated white females) to the different types of exercise for six months. Those exercising lost about 9% body weight on their diets. Resistance training was most effective for preventing loss of muscle and bone mass. This highlights the importance of strength training in helping to prevent frailty, which is a common problem linked to both obesity and weight loss in older adults.
The study supports current UK government recommendations that older adults perform muscle strengthening exercises on at least two days a week.
Why was this study needed?
Obesity is associated with many health problems including heart disease and stroke. Almost a third of people in the UK are obese, costing the NHS around £6.1 billion a year.
Physical frailty is a natural part of ageing but is associated with increased risk of falls and mortality. Obesity can worsen the effects of frailty, but losing weight may cause loss of muscle and bone mass.
Previous studies showed that aerobic and resistance training combined with weight loss improved physical function but didn’t prevent loss of muscle or bone mass or reverse frailty. Aerobic exercise increases cardiovascular fitness with no effect on strength, while resistance training has the opposite effect. The researchers therefore considered that these opposing physiological effects could interfere with each other.
They aimed to compare the two types of exercise when performed alone with the combination of both on preventing frailty during weight loss in older, obese adults.
What did this study do?
This US-based randomised controlled trial included 160 obese adults (aged 65 or more) with mild to moderate frailty as defined by score 18-31 on the Physical Performance Test (PPT).
Participants were assigned to six months of aerobic exercise, resistance training (each 60 minutes three times weekly) or a combination of both (75-90 minutes three times weekly). All groups completed a weight loss programme, including weekly meetings with a dietician, behavioural therapy, and a diet providing an energy deficit of 500-750kcal per day. A control group received no exercise or weight loss programme.
The main outcome was the difference in PPT scores (a composite scale that ranges from 0 to 32 maximum) from start to end of the trial.
Assessors, but not participants, were unaware of group assignment. Participants were mostly female, white, well-educated and physically able to take part. This may limit applicability.
What did it find?
- People in the combination group showed the greatest improvement in physical function, with an increase of 5.5 (+0.4) points in Physical Performance Test (PPT) scores at six months. This was a 21% increase from the average PPT score at the start of the trial. The change was more than the 1.8 + 2.5 points the authors considered a clinically important difference between groups.
- The aerobic and resistance groups showed smaller improvements, with both groups showing an increase of 3.9 (+0.4) points in PPT scores, or 14%, from study start. Functional improvements in all exercise groups were significantly greater than the control group (4% score increase).
- All exercise groups showed a 9% decrease in body weight (<1% in controls), but the combination and resistance groups lost less lean (non-fat) body mass (-1.7kg or -3% and -1.0kg or -2%, respectively) than the aerobic group (- 2.7kg or -5%).
- There was minimal change in bone mineral density at the hip in the resistance group (-0.006g/cm2 or <1% decrease), but some loss in the combination group (-0.014 g/cm2 or -1.1%), and greatest loss in the aerobic group (-0.027g/cm2 or -2.6%).
What does current guidance say on this issue?
The British Society of Geriatrics best practice guidance (2014) states that exercise improves mobility and function for older people with frailty. They say that strength and balance training are key components but the best exercise regimen remains uncertain.
Department of Health physical activity guidelines (2011) recommend that older adults (65+) should aim to undertake at least 150 minutes of moderate intensity physical activity a week. They should incorporate physical activity both to improve muscle strength and improve balance and co-ordination on at least two days a week. Muscle strengthening exercises may involve using body weights or working against a resistance.
What are the implications?
This study demonstrates the importance of resistance training alongside aerobic exercise to preserve physical function and reduce frailty in older adults. This is consistent with Department of Health advice on muscle strengthening exercises.
It is worth noting the specific population studied. Also, the trial was only of six months duration, so it’s uncertain how long these improvements could be sustained.
Other studies have shown that progressive resistance training, where resistance is gradually increased as muscle strength increases, is beneficial for older adults. Structured exercise programmes are likely to be preferable for older adults with frailty, so they can be monitored during exercise to reduce the risk of injury.
Citation and Funding
Villareal DT, Aguirre L, Burke Gurney A, et al. Aerobic or resistance exercise, or both, in dieting obese older adults. N Eng J Med. 2017;376(20):1943-55.
This project was funded by the National Institutes of Health (RO1-AG031176, UL1-TR000041, and P30-DK020579).
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