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.
Here's their key finding from lab tests on mice: Stronger muscles means more
fat burned and a perkier metabolism, even with less-than-stellar diet and
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.
Those mice shed more fat, had livelier metabolisms, and responded better to
insulin (a hormone made by their bodies to control blood sugar) when they were
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
The mice's metabolic benefits stemmed from their type 2 muscle fibers, which
are strengthened by weight training, Izumiya's team notes in Cell
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.