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Along with the coverage in the media about the benefits and pitfalls of ‘fasted cardio’ (exercising in the morning on an empty stomach), there has been a lot of interest recently about how the timing of meals affects your weight [1].

In particular, people have been wondering whether there is any truth in the assertion that eating before bed causes weight gain.

We’ve taken a look at both sides of the argument to answer the question, “Does eating before bed cause weight gain?”

“Yes.” 

Conventional nutritional wisdom would suggest that our metabolism slows when we are asleep, meaning that any food we eat before bed is slower to be digested and used for fuel and more likely to be laid down as extra fat stores. It is also common sense that the longer we stay up, the more likely we are to eat extra calories that we don’t need.

Most people find that the evenings are their time to relax, and often this is in front of the TV, scrolling on their phone or with a book.

These kinds of sedentary activities encourage social eating, boredom snacking and comfort eating. People who stay up late are also less likely to feel refreshed throughout the day and so by the time evening comes, are looking to replenish their energy with fat and sugar instead of the sleep that their body needs.

There is another argument that eating late at night may actually make you hungrier in the 24 hours following your evening eats. Ghrelin, the hormone that controls how hungry you feel, uses the overnight fast to reset itself for the next day.

If you don’t give your body enough time to fast, there is concern that that biological process is hindered [2].

A study focusing on university students found that those with a higher BMI tended to eat most of their calories later in the day, closer to the body’s dim-light melatonin onset, when it prepares for sleep by producing certain hormones [3].

More research is needed to ascertain if the timing of food consumption is significant with regards to weight gain [4].

“No.”

There is no comprehensive study or research to conclude that the timing of food makes a significant different to weight gain.

The reason that people who eat later in the day gain weight may be due to several factors. This may be because they are eating before bed in order to compensate for having skipped breakfast, which would slow their metabolism and induce hunger later in the day, sometimes causing binge eating.

Eating before bedtime also means often eating in dim lighting or the dark, which encourages us to eat as if we are going into hibernation and focus on high fat, high sugar ‘comfort’ foods – it is not the timing of the meals, but what is in them in terms of calories that affects weight gain.

Another factor that may contribute to weight gain in people eating before bedtime is ‘secret eating’- eating when other family members are asleep or busy. This encourages the mindset of ‘invisible calories’, or the thought that food that is eaten outside of meal or snack times ‘doesn’t count’.

Although digestion is slower, the fasting state of being asleep means that all the food is distributed appropriately, and energy stores are used the next day (or laid down as fat if there are excess calories, in the same way it would be if excess calories were eaten earlier in the day).

If you are tempted to snack in the evening have some low calories snacks such as vegetable crudites pre-prepared so that you don’t reach for the high calorie foods.

Conclusion

Eating before bed can cause weight gain, but this is not down to the timing of the food. Eating late at night means that you may be consuming more calories than your body needs, especially as foods that are high in fat and sugar are particularly appealing during times of relaxation.

The best way to control your weight is to eat a healthy, balanced diet throughout the day, avoiding extreme hunger which could cause binge eating and also avoiding being too full after consuming excess calories.

Hannah Canavan
Hannah Canavan
Researcher at DietProbe
Hannah is a health and lifestyle journalist with a passion for veganism and nutrition.
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