12% calorie restriction builds stronger muscles

What's the news: Calorie restriction builds stronger muscle and activates healthy aging genes.

Why should we believe it: This news is based on a new study published last week by scientists at the National Institute on Aging. The scientists used data from the CALERIE study, which took 220 healthy adults, ages 20 to 50, and submitted them to 2 years of 12% caloric restriction. The result of this regimen:

• A drop in body weight (good) and a drop in muscle mass (not good)

• In spite of the drop in muscle mass, no drop in strength (meaning the remaining muscles got stronger)

• Upregulation of genes responsible for energy generation and metabolism (probably why the muscles got stronger)

• Downregulation of inflammatory genes, leading to lower inflammation (good, since inflammation ramps up as we age)

Why this is a big deal: In the words of NIA Scientific Director Luigi Ferrucci, "A 12% reduction in calorie intake is very modest. This kind of small reduction in calorie intake is doable and may make a big difference in your health."

At the same time, the effects of long-term calorie restriction in humans are still unclear (again, the above study ran for two years). Longevity researcher Valter Longo, the Director of the Longevity Institute at USC, has said before that permanent calorie restriction is not for humans, because it can slow metabolism, cause frailty, and weaken the immune system.

So what specifically can you do now: First off, decide whether you want to practice calorie restriction, and for how long. (Again, permanent calorie restriction might not be a winning strategy.)

If you do decide that calorie restriction is something you want to try for a while, you can track your calories and make sure you get exactly 12% less than your standard calorie intake. That might require a level of obsessiveness. An easier and more sustainable strategy is just to follow the Japanese practice of Hara Hachi Bu — eating until you feel 80% full.