There are a couple of theories:

• Partial sleep deprivation results in greater activation of areas in the brain associated with reward – fattening foods in this case.
• Disruption of the internal body clock affecting your regulation of leptin (the satiety hormone) and ghrelin (the hunger hormone).
• Lack of sleep gives you the munchies like weed. Erin Hanlon, PhD, notes: "Sleep restriction boosts a signal that may increase the hedonic aspect of food intake, the pleasure and satisfaction gained from eating. It seems to augment the endocannabinoid system, the same system targeted by the active ingredient of marijuana, to enhance the desire for food intake."

Interestingly, most of the subjects in the studies didn't go for carbs as you'd expect, but more dietary fats. They also consumed less protein when sleep deprived.

Although the researchers in the above meta-analysis didn't mention it, other studies have concluded that when healthy young men sleep 5 hours or less per night for a week, their testosterone levels take a dive.

Generally that means less muscle, less energy and more body fat over time. Five hours of sleep per night decreased subjects' testosterone levels by 10 to 15 percent in one study, and these guys were in their early 20's.

If sleep evades you and the whole slowly-get-fat thing doesn't sound fun, then along with the usual "put down your damn devices and sleep in a cool room" advice, consider supplementing with ZMA®.

1. Al Khatib HK et al. The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis. Eur J Clin Nutr. 2017 May;71(5):614-624. PubMed.
2. RLeproult R et al. Effect of 1 Week of Sleep Restriction on Testosterone Levels in Young Healthy Men. JAMA. 2011 Jun 1;305(21):2173-4. PubMed.
3. Hanlon EC et al. Sleep Restriction Enhances the Daily Rhythm of Circulating Levels of Endocannabinoid 2-Arachidonoylglycerol. Sleep. 2016 Mar 1;39(3):653-64. PubMed.