The claim: Just a few days of fasting can trigger the breakdown of skeletal muscle--an alarming prospect for sick or older adults who may already suffer from weakness or loss of muscle. On the other hand, there’s some evidence that the cellular processes related to this muscle breakdown might--in small doses--actually be beneficial for strong, healthy adults.
The research: A team from Aarhus University Hospital in Denmark examined the muscles of eight healthy men before and after a 72-hour fast. After skipping meals for three days, the men experienced a 50 percent reduction in mTOR activity, a key regulator of muscle cell growth. Put simply, when mTOR drops, muscle wasting speeds up. That may sounds like a bad thing, but, oddly, there’s evidence from rodent studies that blocking mTOR activity triggers “cell survival responses” that can actually extend life, says study coauthor Dr. Mikkel H. Vendelbo.
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What it means: Even if you’re young and healthy, skipping meals for any extended period of time could lead to the type of weakness and fragility seen among older or unwell adults, Vendelbo explains. There’s also plenty of research showing that missing meals will further speed up muscle loss and weakness among the sick and the elderly--groups that already have a hard time holding onto skeletal muscle. But for healthy, robust adults, fasting for short stretches could actually be good for you, Vendelbo says. Science hasn’t actually figured out how slowing the mTOR signaling that leads to cell growth could help people (or at least rats) live longer, Vendelbo adds. But there’s some human-based evidence from the UK that shows temporary bouts of fasting can help people live longer.
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The bottom line: Your muscles are your strength. They allow you to hold up your head and move your eyeballs as you read this story. For many adults--especially seniors and those enfeebled by illness--losing muscle is a daily battle. Vendelbo’s research helps explain exactly how skipping meals can speed up muscle loss. And while there is some animal- and human-based evidence that fasting for short stretches could offer healthy adults some benefits, it's way too early to suggest it as any sort of health strategy (and it's definitely never a good weight loss one). At this point, there are still a lot of unanswered questions, Vendelbo adds.