Question: I’m training hard and eating right but not losing fat. What am I missing? –@greensitt_s

Answer: Consider how you’re sleeping. Getting fewer than seven hours per night can reduce and even undo the benefits of dieting, according to research published in the Annals of Internal Medicine. The study found that when dieters cut back on their sleep, the amount of fat they lost also got cut—by more than half (55%)—even though they remained faithful to their diet. The subjects also felt significantly more hungry, were less satisfied after meals, and lacked energy to exercise.

When you’re sleep deprived, your body suffers from metabolic grogginess, a term coined by researchers at the University of Chicago, who analyzed what happened after just four days of poor sleep (a typical week for busy guys). In that time, your fat cells become up to 30% less sensitive to insulin. This leads to your storing more fat, particularly in your liver, and puts you on the road to type-2 diabetes. And there’s bad news for your muscles too: Getting fewer than six hours of sleep for a week can cause testosterone to drop by up to 15%.

So hit the weights, eat your protein, DVR your favorite shows, and then get to bed. You need seven to nine hours of rest per night.

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