Why We Crave Junk Food: Part 3 — Sleep and Satiety

Sometimes I get a huge craving for some chips. Most of these times the craving ends up passing before I buy any, since I don’t keep them in my house. And the truth is the last time I even ate chips was several months ago. When I get these cravings, I have noticed that either I am super stressed, or I have been having a difficult time sleeping and feeling the effects of the lack of quality sleep.

What We Have Discussed So Far

In part one of this series, we talked about what characteristics ultra-processed have, the detrimental effects and how they activate the pleasure center of our brain. Then in part two we discussed the effects of stress on our cravings for junk food. Today we are moving on to look at how sleep and satiety affect our consumption of processed foods.

The Effect of Sleep Deprivation

Neuroimaging research has shown that pleasure-related portions of the brain are more strongly activated by energy-dense meals during sleep restriction This means that when we are sleep deprived, energy-rich foods simply taste better.

There have been several research studies showing that sleeping less increases consumption of energy-dense, highly processed meals and snacks. In one study subjects who had three nights of sleep restriction had a higher level of the hunger hormone ghrelin compared to those who did not. These subjects ate an additional 340 calories the next day on average, with 280 coming from sweet and salty snacks. The most intriguing aspect about this research is that they don’t even have to limit their sleep by a significant amount to get responses. Even with realistic sleep restriction such as going from six and a half hours of sleep per night down to just six hours of sleep subjects are more likely to eat more calories with a significant portion of those calories coming from junk foods.

Why We Are Not Satisfied

Next, we’ll look at how energy-dense highly processed foods affect our satiety. In dietetics, energy density refers to the amount of energy in each gram of food; strawberries, for example, have around 30 to 40 calories per 100 grams while potato chips have about 500 calories or more per 100 grams.

When people are presented with different forms of food that are similar in flavor but varied in energy density, they generally eat a consistent amount of food. One study compared two diets with a 300-calorie difference in energy density. The subjects consumed equal amounts of both diets, implying the difference in calorie intake between the two groups was 300 calories. Neither group perceived a difference in fullness compared to the other. This means the size of the meals we eat has an impact on how much we consume throughout a meal. This plays a role during a meal because physiological signals linked to differences in energy density may not have time to register meaning our intake will be governed by more immediate indicators such as the amount consumed. We cannot rely on digestion alone because meals don’t last long; therefore, we need more upfront indications like the volume of food we’re eating and how long we’ve been eating it.

Up until recently, these upfront cues were sufficient since we weren’t surrounded by such high-energy dense foods in the wild like we are now. We’ve got our hedonic system, which is our reward system informing us that this high-energy dense food is fantastic, and we’ve also got a homeostatic system that keeps us in energy balance to avoid overeating. What happens is that our homeostatic mechanism cannot easily take into account how much more efficiently we are eating calories.

How To Combat Junk Food

All of this leads us to the fact that we generally must be more mindful of what we are eating. As I have mentioned before, I am not an advocate of cutting out foods that bring us joy. Yes, I do believe it is our responsibility to try to eat healthy much of the time with a goal of 70 to 80% of our food being unprocessed and not laden with sugar and fat. But that leaves room to plan in your favorite junk foods.

You do not have to cut out these junk foods entirely if you include them as part of a well-rounded nutrition plan. It is when we do not have a plan or are unaware of the differences in calorie density and lack of micronutrients that we overindulge and affect our health. I encourage you to come up with a plan to enjoy your favorites in moderation and be mindful of the factors that influence your eating.

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