Lifting while dieting saved almost all the muscle older adults would have lost

Weight loss through calorie restriction does not discriminate between fat and muscle: some of what disappears is lean tissue. For obese older adults this is a serious trade-off, because muscle is already declining with age and losing more of it threatens strength and function. Resistance training is the obvious candidate to protect muscle during a diet, but the extent to which it can actually attenuate diet-induced muscle loss in humans had remained unclear. This review set out to quantify that protection by summarising the trial evidence in obese elderly individuals.

The authors systematically searched MEDLINE, Embase and Web of Science between July and August 2017 for randomised clinical trials comparing calorie restriction alone against calorie restriction combined with resistance training in obese elderly individuals. Six trials met the criteria. All applied resistance training three times per week for 12 to 24 weeks, and most calorie-restriction diets were composed of 55% carbohydrate, 15% protein and 30% fat. Outcomes were lean body mass, fat body mass and total body mass, all measured by dual-energy X-ray absorptiometry, a precise body-composition scan.

Adding resistance training reduced 93.5% of the lean mass loss induced by calorie restriction, a difference of 0.819 kg compared with dieting alone. Crucially, this protection came at no cost to the diet's purpose: reductions in fat mass and total body mass were similar whether or not participants trained. There was also a suggestion of improved muscle quality, with the ratio of strength to lean mass tending to move in opposite directions between groups, rising around 20.9% with training while falling around 7.5% without it, though this difference did not reach statistical significance.

This synthesis puts a number on something long suspected: resistance training can prevent almost all of the muscle loss that calorie restriction causes, at least in obese older adults over three to six months. It strengthens the case that dieting and lifting are complementary rather than competing strategies, since fat loss was undiminished. The evidence base is small at six trials, all in one population, so how far the protection extends to younger dieters, leaner people or longer diets remains open, as does whether the hint of improved muscle quality would firm up in larger studies.

If you are losing weight through calorie restriction, this is a reason to think that resistance training is not merely an optional extra but the difference between losing fat and losing a mix of fat and muscle. The pooled trials suggest the protection is nearly complete in obese older adults, and that adding training did not blunt fat loss at all. The evidence comes specifically from obese elderly participants training three times weekly, so it describes that context rather than guaranteeing the same result for everyone.