Does Eating Before Bed Cause Insomnia? (Science-Backed)

Eating shortly before bed (1-2 hours) increases your chance of sleep trouble.

A 2011 study sums it up well (1):

We conclude that food intake during the nocturnal period is correlated with negative effects on the sleep quality of healthy individuals.

That’s the high level conclusion anyways.

But there’s some nuance as well. It turns out that some night eating is worse than other night eating (e.g. a small snack isn’t usually a big deal).

We’re going to look at the research around this topic on this page to get to the bottom of this issue.

Side note: If you ever want to explore more about this issue, searches around “evening hyperphagia” are your best bet.

Other Side Effects of Night Eating

Sleep trouble is not the only potential side effect of night eating.

Research shows that people with a night eating habit are more at risk for other consequences including:

1. Depression - One study found that 55.7% of their night eating subjects experienced clinical depression at some point in their life (2).
2. Anxiety and eating disorders - That same study mentioned just above also found subjects were fairly likely to develop anxiety and eating disorders.
3. Food addiction - While a specific type of eating disorder, other studies have found that people more prone to night eating are more likely to have a food addiction (3).
4. Weight gain - It’s not exactly surprising that there’s a big overlap in people with frequent night eating and obesity (4).

Note that night eating doesn’t necessarily cause all these issues, it could be the other way around. Studies have shown that night eating is associated with emotional eating, so it could be that things like stress and depression cause people to cope through extra eating (5).

SummaryFrequent night eating can be a sign of a bigger problem that will affect not only sleep but other aspects of health.

How Common is Sleep Trouble for Night Eaters?

Many people eat at night and don’t have sleep issues.

One study found subjects in an obesity clinic and looked at the overlap between not eating in the morning and sleep issues (6).

They found that 27 out of 55 (about 50%) of patients with evening hyperphagia (substantial night eating) also had sleep problems.

Even though obesity is a risk factor for insomnia, the subjects were all obese so that helps factor in obesity as the cause of the sleep issues.

SummaryWhile not much research has been completed on this specific question, sleep trouble is very common for people who eat a significant amount of calories at night.

How Long Before Bedtime Should You Eat?

A research team gave 12 subjects 3 different meals (with the same calories), one week apart for a test (7):

• Low glycemic index (GI) meal 4 hours before bedtime
• High GI meal 4 hours before bedtime
• High GI meal 1 hour before bedtime

Rice was given for both meals, but a high GI variety (i.e. white) and low GI variety (i.e. whole wheat)They found a significant result for both variables tested.

First the high GI vs low GI meal:

A significant reduction in the mean sleep onset latency (SOL) was observed with a high-GI compared with a low-GI meal consumed 4 h before bedtime. 

This means that the high GI (i.e. fast digesting, usually has less fiber) helped subjects fall asleep faster.

In other words, the longer it takes for food to digest, the more it impacts sleep. Foods high in things like fat and fiber take a long time to digest.

Next, the result for eating 4 hours before bedtime compared to 1 hour:

The high-GI meal given 4 h before bedtime showed a significantly shortened SOL compared with the same meal given 1 h before bedtime (9.0 +/- 6.2 min compared with 14.6 +/- 9.9 min; P = 0.01).

In other words, eating 4 hours before bed was significantly better than eating 1 hour before.

Note that they didn’t go any further than that, so it’s possible that eating 2 hours is better than 4 for all we know.

SummaryEating high GI food (e.g. easy to digest carbohydrates like white rice or certain fruit) is better for sleep than low GI food. Additionally, eating at least a few hours before bed is better for sleep quality than eating an hour or less before bed.

Is All Night Eating Equally Bad?

As suggested above, sleep trouble may only be caused by certain types of night eating.

There are 3 main factors that I’ve identified after reviewing the research I found:

• The type of food eaten
• The amount of food eaten
• The macronutrients (i.e. high fat vs high carbohydrate)

Let’s quickly go through them individually.

Type of Food

While a lot more research is needed, data is starting to suggest that (8):

Negative outcomes may not be consistent when the food choice is small, nutrient-dense, low energy foods and/or single macronutrients rather than large mixed-meals.

In other words, a small healthy snack (i.e. a banana) isn’t likely to have much of an effect on sleep. For people who exercise vigorously, a small snack in the evening may even help recovery.

Eating a salad before bed isn't the worst, but it's not great. High fiber vegetables take quite a while to digest.

On top of that, certain foods are known to have detrimental effects on sleep quality. For example, chocolate consumption is linked to insomnia, along with caffeine, spicy foods, and others. Note that even though sugar is very high GI, there's a link to sugar and insomnia, which is why it's important to stick to "healthy" foods if eating at night.

Amount of Food

One study found a moderate correlation between the amount of food eaten at night (in terms of calories) and how long it took for subjects to fall asleep (9):

The correlation held for both men and women, but was slightly stronger when looking at just women alone.

Macronutrient Content

In that same study mentioned just above, they also looked at both carbohydrate and fat content in evening meals.

For men, they found:

The correlation between dietary and sleep variables in men indicated a negative association between nocturnal fat intake, and sleep efficiency, and REM sleep, and a positive association between nocturnal fat intake, and sleep latency, and wake time after sleep onset.

In short, high fat meals were associated negatively with multiple sleep quality metrics.

For women, they found:

In women, there were positive associations between sleep latency and caloric, protein, carbohydrate, and fat nocturnal intake.

So while the negative effects in men were largely limited to meals high in fat, women suffered sleep issues regardless of whether food was high fat or high carbohydrate.

That’s quite an interesting finding and I hope this will be studied in more detail, because there’s obviously quite a bit of complexity and nuance here.

SummaryWomen are more likely than men to have sleep issues after eating before sleep regardless of what they eat. In general, eating a small amount of healthy food is less likely to cause any insomnia symptoms.

Summary: How Eating Before Bed Affects Sleep Quality

It’s clear that more research needs to be done, but we have a decent picture of how eating before bed affects sleep, and in general, most people benefit from going to sleep on an empty stomach.

In summary:

• The majority of people who frequently eat meals shortly before bed suffer sleep trouble. That can range from taking longer to get to sleep, to full on insomnia.
• Research shows that eating 4 hours before bed is much better than eating 1 hour before bed. There’s currently not enough research to get more specific than that.
• Eating small healthy meals at night is much less likely to cause any issues in sleep quality than eating large meals that contain unhealthy foods or “trouble” foods (e.g. chocolate, spicy foods).
• Women appear to be more likely to develop sleep issues after eating at night than men.

Overall, it’s very possible for night eating to cause sleep trouble, so it’s better to avoid it when possible.

References

1. Relationship between food intake and sleep pattern in healthy individuals
2. Nighttime eating: A descriptive study
3. Validation of the Night Eating Diagnostic Questionnaire (NEDQ) and its relationship with depression, sleep quality, “food addiction”, and body mass index
4. Correlations between night eating, sleep quality, and excessive daytime sleepiness in a severely obese UK population
5. Night eating is associated with emotional and external eating in college students
6. Night eating and nocturnal eating—two different or similar syndromes among obese patients?
7. High-glycemic-index carbohydrate meals shorten sleep onset
8. The Health Impact of Nighttime Eating: Old and New Perspectives
9. Relationship between Food Intake and Sleep Pattern in Healthy Individuals