In my  last blog I discussed how eating late at night doesn’t necessarily lead to weight gain, but because many of the studies gave varying results, the conclusion is inconclusive. However, a few sources did mention that it may be because of our junk food intake around the time we go to bed that makes it seem like we are gaining weight due to eating late. If this is the case, then I’m here to ask why. Why are we craving salty, sweet, and all around unhealthy snacks after the sun goes down? What is it about the nighttime that makes us want junk food? As promised, I’m here to tell you.

As it turns out, not a lot of research has been done on the subject, but there are a few theories and experiments out there that either say one of two things: junk food cravings at night are psychological, or they are caused by sleep deprivation.

Psychological: There are few studies done on psychological junk food cravings that are experimental, however, psychologists have done correlational research by observing trends in people who have a tendency to eat junk food at night. One website poses multiple explanations as to why we seek out unhealthy foods after dark. Among them is that the undercover feeling of night allows us to feel less guilty about deviating from what we believe to be acceptable behavior. Another is emotional eating–whether it be due to loneliness, depression or another emotion–causes us to seek out comfort in foods that increase dopamine (chemical in the body that plays a role in happiness) levels. Although, there is an insufficient amount of research to confirm or support the validity of such hypotheses, both of them have yet to be rejected.

On the other hand, one theory that has been researched more extensively is the theory of willpower. According to the aforementioned source as well as a study by Massive Health, people are eating unhealthier foods as the day goes on which could be due to their willpower decreasing as time progresses. Since “willpower is a finite substance,” the longer you fight off the urge to succumb to junk food, the more likely it will run out by bedtime. This causes you to give in and eat the high-calorie foods. Then again, this is simply a correlational study and we all know, correlation does not equal causation.

Sleep Deprivation: The next explanation for why we crave junk food at night is sleep deprivation. Despite the fact that there are more credible studies done on this topic, they all differ. To begin, one study done by Brigham Young University took 15 women and showed them pictures of high and low-calorie foods while scanning their brains once in the morning and again in the evening a week later. As it turns out, the area of the brain associated with reward “didn’t react as strongly to images of food in the evening as they did in the morning” which brought the researchers to conclude that “if we see food as less rewarding” it will continuously cause us to go back for more “until we feel satisfied.”

Another study discussed in this article begs to differ. St Luke’s-Roosevelt Hospital Center and Columbia University took 25 men and women and conducted MRIs on them while they, once again, looked at pictures of healthy and unhealthy foods. After exposing subjects to two different conditions (five nights of sleep for nine and four hours), contrary to the other study, the areas of the brain associated with reward reacted more strongly to the higher-calorie foods. Researchers explained that “under restricted sleep, individuals will find unhealthy foods highly salient and rewarding, which may lead to greater consumption of those foods” and “when you’re fatigued, your body would want calorie-dense foods that give you quick energy.” A third study published in the medical journal, Appetite, backs up this conclusion with a correlational study which found that, if participants slept “a little more than an hour and a half extra,” their overall appetite would go down by 14% and their cravings for junk food would decrease by 62%.

So what does all of this mean? Well, in terms of the psychological relationship with junk food cravings, more research should be done, and the same goes for the sleep deprivation hypothesis as well. Even though, the theory regarding sleep deprivation is more reliable in terms of experimental design (as opposed to correlational), all of the studies used small sample sizes and were subject to many confounding variables as well as reverse causation.

What is the takeaway message from all of this? Well, since there is no clear answer to the question “Why do we crave junk food at night?” the decision is yours. If you’re one of those people who finds yourself snacking before bed, maybe try healthier options instead–like fruits or vegetables. If those kinds of foods aren’t your thing, you could try going to sleep a little earlier to avoid the temptation sleep deprivation may or may not bring on, or you can carry on with your midnight snacking because it’s just too difficult to resist. I know I’m not going to take my chances with the weight gain I discussed previously, so I’ll either resist the temptation to my fullest ability or just consume my higher-calorie foods during the day. Even though, all of the studies discussed could be due to chance, sometimes the risk isn’t worth it.