Until pretty recently, food has really just been thought of as fuel (at least in the Western world) - based on its nutritional constituents like the carbs, vitamins and minerals it contains as well as the calorie content.
But what we’re discovering is that food is much more than just the nutrients it contains. The health giving and nutritional components of food actually depend on the interaction they have with the body…..
What do I mean by that?
Let me explain by talking about Chrononutrition.
Chrononutrition is the science behind how meal timings of food interact with your body clock and metabolism.
Good nutrition is so much more than just the components of a food, but also how the body is working to digest, absorb and utilise the nutrients contained within food.
You can eat the healthiest foods on the planet but if you’re not digesting or processing them effectively, then you will not experience the full benefits of them.
So what does this have to do with eating late at night?
Well, as it turns out our bodies have become adapted to most effectively deal with the digestion and metabolism of food during waking (daylight) hours.
This is all to do with our circadian rhythms (or body clocks), and their synchronisation with the rhythm of night and day.
Food is something that can help us tune our body clocks to be in line (or out of line) with the external environment. We use food as what's known as a timekeeper, to help us align our internal body clocks to the daily environmental rhythms each day.
So if you think of each meal time during the day, you are using it as a means to help your internal body clock keep time with the progression of the day. This all depends on whether meals are eaten in the typical daily fashion, usually within waking hours (when it's light).
Generally, when it’s light it's also a good time to eat because the daylight is also helping your internal body clock keep time with the stage of the day.
What Happens When Eating Late at Night?
So when the sun goes down and the light fades away, this is a cue for the body to start changing its internal state in preparation for sleep. Hormones follow a daily circadian rhythm, in a way which helps give us energy, metabolic prowess and digestive fire (capacity) in the day, and to promote sleep and restoration in the evening.
Obviously we eat evening meals when it’s already dark, in the winter months which is fine. The body has begun its winding down state, and it's not yet in full swing when it comes to shutdown mode for optimal rest and repair. This is if we eat no later than 8-9pm, roughly.
So what happens when we eat later than this?
One timekeeper (lack of light/darkness) is telling us that it’s time to wrap things up for the day, causing us to tone down our metabolic capacity, and digestive efficiency in order to devote energy towards repair and restoration.
If we are also eating at this time, then we are using another timekeeper (food) to pull us in the other direction and putting demand on our digestive and metabolic systems when they are being told to wind down. This also steers energy away from the restorative processes that occur at night.
This is why research shows that eating foods later at night, is actually met with a worse metabolic response to those foods.
Eating later at night can increase the chances of weight gain from that food. This is due to the fact that food is met with a worse metabolic response at night - it raises blood sugar more, impairs fat metabolism, and requires more insulin to get sugar into cells, as well as increases blood lipids such as cholesterol and triglycerides (*).
What you have here is basically the early developments of diabetes and obesity, as well as some developmental risk factors for heart disease.
We know that (night) shift work is associated with a significantly increased risk of diabetes (*) and obesity (2.3x more likely) (*), as well as other chronic diseases (*). So it’s safe to say that it's the interaction of food with time of day that's behind this, based on the biological responses we talked about above.
This interaction is made worse when the foods are high in carbohydrates (*), especially simple ones like crisps, bread, sweets and general snacky foods. The body is not well equipped to deal with any food during the night time, but it appears that due to the fact that cells are more insulin resistant at night, eating (simple) carbs is bad for blood sugar and also sleep quality.
It’s not just metabolic problems that can occur. Dawn Loh from the UCLA Laboratory of Circadian and Sleep Medicine says, ”taking regular meals at the wrong time of day has far-reaching effects for learning and memory”.
This was established from a study that showed that mice had a reduced activity of a key protein, CREB, (cAMP response element-binding protein), related to memory capacity when they were fed out of sync with normal eating patterns (*).
When CREB is less active, it reduces memory capacity and is even related to the onset of Alzheimer’s.
This also explains why shift work is associated with an increased risk for dementia (*). But it's not just the eating, it's also being out of sync in general that's probably the leading cause.
Does Portion Size or Food Type Matter?
If we dig a little into this, it appears that the ‘bad’ responses to food at night depend on two main factors (at least in relation to metabolism):
- The type of food it is - fat, protein or carbohydrate
- The amount of food
For example, a (small) high protein snack (30g) eaten up to 30 mins before bed may actually help metabolism and muscle quality (*). The study looked at cottage cheese, but other high protein foods like a protein shake or peanut butter could also work.
Small snacks have actually been shown to be ok closer to bedtime. A study found that nighttime consumption of small (~150 kcals) single nutrients or mixed-meals does not appear to be harmful and may be beneficial for muscle protein synthesis and cardiometabolic health (*).
A small mixed meal may be a very small bowl of yogurt with berries, or an apple with peanut butter for example.
It really seems as though the real interruption to sleep quality as well as metabolism is often when a large, carbohydrate rich meal is consumed closer to bedtime or later at night.
Favoring protein and fat for night meals has shown to be beneficial for post meal blood sugar, which may prevent interruptions to sleep (*). But again, keep them light.
Why do you eat late at night?
It’s all very well knowing that eating late at night may not be the best option, but what if it's become a habit?
Well as we’ve discussed above, if eating late at night make it a low calorie, high protein low carb snack (not a meal).
A few examples of these snacks would be:
- Peanut Butter with Yogurt and Protein powder, with a few berries
- Cottage cheese with some nuts
- An Apple with A Nut Butter
- Protein Shake
If you’d like to ditch it all together though, consider why you may feel the urge to eat late at night. What is the underlying desire to do so - is it because of stress, boredom maybe?
Once you explore this, you can perhaps adopt a stress management technique instead of using food as a crutch, or if boredom perhaps explore a new hobby around this time at night.
If it’s your work or routine that makes it hard to not eat late at night, then perhaps you could fix something to eat at the office, before you leave for home? Or maybe even just skip the evening meal on some days as an intermittent fast has been shown to be pretty good for metabolic and immune health.
Maybe you could even prepare a meal at home to eat earlier in the evening before commuting?
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Take a look at our marketplace of meal preppers, and find a flavor that's right for your goals, and your schedule.
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The takeaway or TL:DR from today was basically that our bodies are not well equipped to deal with food or eating when its during the night, when we are usually sleeping and our bodies are meant to be resting, repairing and regenerating.
Living out of alignment with the cycles of night and day can lead to some health issues long term.
There are ways to get good quality nutrition on board close to bedtime, but it needs to be a small snack (~150 calories) that is mostly protein and fat, and low in carbohydrates.
Changing your evening routine and habits (where possible) may lead to better sleep and health longer term.