The researchers aren't talking about fitting into a smaller-sized pair of jeans or shrinking the numbers on the scale. Instead, they're focused on the metabolism benefits of getting stronger at any size.
But there's a catch. Muscles don't stay that way without work, so you've got to be in it for the long haul to keep reaping the benefits.
Yasuhiro Izumiya, MD, PhD, and colleagues used genetic engineering to turn a certain muscle gene off and on in mice.
When the gene was on, the mice got a lot more muscular and stronger, mimicking the effects of weight training.
But when the gene was switched off, the mice lost their buff physiques, as if they'd slacked off a strength-training program.
That pattern held even when the mice ate fatty, sugary chow and didn't get much exercise. However, those mice did wind up fatter than active mice on a healthier diet.
The mice's metabolic benefits stemmed from their type 2 muscle fibers, which are strengthened by weight training, Izumiya's team notes in Cell Metabolism.
But strength training is just one part of fitness. In Izumiya's study, when the mice got very muscular, their grips became stronger, but they didn't fare too well on a treadmill test. So while weight training may help with weight loss, endurance training is still important.
Consult your doctor before starting a new exercise program, especially if you've been on the sidelines for a while.