By Denis FayeRecently, the media branded the "Don't Eat Before Bedtime" rule as a myth. As usual, they've taken a complex topic, distilled it down to a catchy headline, and gotten it completely wrong. The correct answer is much more nuanced. The short answer is that sometimes it's okay to eat before bed, but mostly, it's probably a bad idea.
The old thinking was that when you ate before bed, your body would be more prone to store food as adipose tissue—in other words, as fat. This might be an oversimplification, but current research indicates there's truth to this supposed myth. A 2009 Northwestern University study separated mice into two groups and fed them both high-fat diets. They allowed half the mice to eat at night, which happens to be the normal feeding time for the nocturnal rodents. The other group ate during the day, when they'd normally be sleeping. By the end of the study, the night eaters had a 20% weight increase and the day eaters weight went up 48%.(1)
The researchers credited the weight gain to a domino effect that began with the disruption of circadian rhythms (the biological clock that indicates what your body needs and when it needs it every 24 hours). Knocking these rhythms out of whack caused an imbalance of leptin—a satiety-regulating hormone that's heavily influenced by the amount you sleep.
In 2011, Northwestern published another study that further supported the results of the first. This one tracked 52 human subjects over a week. The results indicated that "caloric intake after 8:00 PM may increase the risk of obesity, independent of sleep timing and duration."(2) While neither of these studies is conclusive (one wasn't on human subjects, and the other worked with a limited sample size), they're both compelling.
That said, there are a couple times when eating before bed is okay. If you're trying to build muscle, casein protein (found in dairy but available in pure, powdered form) before bed might be worth trying. According to a study in the August 2012 issue of the Journal of Medicine & Science in Sports & Exercise, men who strength-trained for an hour, consumed 40 grams of casein, and then hit the sack experienced a 22% rise in amino acid circulation for the full 7.5 hours of sleep. In other words, the protocol gave their muscles better access to the building blocks they need to recover and grow.(3)
Also, consider those hectic days when you just haven't had time to eat during the day. (Not ideal, but we don't live in an ideal world.) Add to this the hard workout you did. In these situations, your priority should probably be to replenish lost nutrients such as electrolytes and make sure your body has all the protein (among other things) it needs for recovery. You don't need a four-course dinner, but a light, balanced meal would be to your benefit.
Finally, there's the psychological factor to consider. Last night, my 8-year-old said she couldn't sleep because she was hungry. I chopped her up an apple. We chatted as she ate half of it. Then, she shuffled off to bed and slept just fine, circadian rhythms be darned. We all have an inner 8-year-old, so sometimes, you're going to find it easier to sleep with a little somethin'-somethin' in your tummy. I wouldn't suggest institutionalizing the nighttime snack, but if you need the occasional piece of fruit or air-popped popcorn to detangle your nerves and send you off to dreamland, it's not the end of the world.
In general, though, here's what I recommend: If you're trying to lose weight, stack the deck in your favor and go to bed on a relatively empty stomach. You can follow the 8 PM rule of the second study or, if that's just not going to work with your schedule, then avoid eating within 3 hours of going to bed. Or, if you're trying to build mass, supplement with casein before bedtime.
- Arble, Deanna M et al. "Circadian timing of food intake contributes to weight gain." Obesity Silver Spring Md 17.11 (2009) : 2100-2102. (http://www.nature.com/oby/journal/v17/n11/full/oby2009264a.html)
- Baron, Kelly G et al. "Role of sleep timing in caloric intake and BMI." Obesity Silver Spring Md 19.7 (2011) : 1374-1381. (http://www.nature.com/oby/journal/v19/n7/full/oby2011100a.html)
- Res, Peter T et al. "Protein Ingestion Prior To Sleep Improves Post-Exercise Overnight Recovery." Medicine & Science in Sports & Exercise 44.January (2012) : 1. (http://www.ncbi.nlm.nih.gov/pubmed/22330017)