I hear a lot of dieters saying you should never eat late at night.
Carbs in particular are often highlighted, as if they somehow take on a magically different structure once the clock strikes a certain time.
I often find myself wondering where these ideas come from in the first place.
I mean, it’s important to question if there’s any science to back up the notions we have about dieting, or if they are merely anecdotes.
I’m not against anecdotal evidence completely, but things get a bit rocky if that’s all you’re relying on.
I suppose there are many things in the diet-world that have become accepted as fact, when in reality they are nothing more than theories, that have been repeated loudly enough so people eventually start believing them to be true.
And, there are a lot of theories about carbs floating around these days. As I discussed recently, it can get super confusing at times.
So, is there any truth to the idea that eating carbs at night makes you fat, fast?
Carbs At Night
So, when you eat high carb foods later on, there’s a greater chance they will be stored as fat, compared to eating carbs earlier in the day, where there is more chance they would have been burned off.
Sounds reasonable — you lie down, you move little, you burn fewer calories, right?
But, while that appears to make some sense…
The research shows it’s more complicated than that;
- Energy expenditure decreased during the first half of sleep by around 35 percent. But, during the latter half of sleep, it significantly increased, associated with REM sleep.
- This seems to be inline with resting metabolic rate (RMR), which also rises and falls throughout the day.
- However, in another study, obese individuals had sleeping metabolic rates lower than their resting metabolic rates, whereas lean subjects had sleeping metabolic rates significantly higher than their resting metabolic rate.
- From all of this, we can gather that metabolism actually increases while you sleep, unless you are obese.
In fact, there’s an interesting school of thought that eating most of our carbs at night, could help us get, and stay, lean.
This idea isn’t new.
In the powerlifting and strength training arena they call it carb back-loading, originally coined by John Kiefer.
In essence, the protocol relies on taking in very low quantities of carbohydrate in the morning, then higher amounts of carbohydrate after resistance training, towards the end of the day.
Again, it’s good to question the theory, and interestingly, I found a recent study relating to this idea of carb timing.
In the study, participants were put on a calorie restricted diet for six months;
- Either a control group (carbs throughout the day).
- Or, the experimental group, who ate their carbs mostly at dinner (approx 80% at night).
- The groups ate the same amount of calories, protein, carbohydrates, and fat (1,300–1,500 kcal, 20% protein, 45–50% carbohydrates, 30–35% fat).
- The only difference was how they distributed their carbohydrate intake.
- They all had BMIs greater than 30 to begin with.
What did the researchers find?
Well, the group eating their carbs at night, lost more weight (11.6 vs 9.06 kg) and body fat, compared to the control group.
On top of that, they also experienced better satiety levels, which I think it highly significant;
Greater weight loss, abdominal circumference, and body fat mass reductions were observed in the experimental diet in comparison to controls. Hunger scores were lower and greater improvements in fasting glucose… A simple dietary manipulation of carbohydrate distribution appears to have additional benefits when compared to a conventional weight loss diet in individuals suffering from obesity. It might also be beneficial for individuals suffering from insulin resistance and the metabolic syndrome.
It all sounds pretty promising.
So, why is it that eating most of your carbs in the evening could be beneficial to body composition, and satiety levels?
First of all we need to understand a little about cortisol, since it plays a key part in all of this.
Cortisol has received a lot of flak in recent years, but it is actually a vitally important hormone.
It naturally peaks when you wake up, this is known as the cortisol awakening response (CAR). Also, exercise and acute stress significantly raise cortisol levels.
How Cortisol Works
Cortisol (and its partner epinephrine) is best known for its involvement in the “fight or flight” response. Which works as follows;
- You are faced with something stressful.
- The adrenals secrete cortisol.
- Cortisol prepares the body for a fight or flight response, by increasing glucose in the blood to supply an immediate energy source to your muscles.
- Cortisol inhibits insulin production, to prevent glucose from being stored, since you want to use it immediately.
- You address or resolve the situation.
- Your hormone levels begin to return to normal.
Obviously, this works perfectly well under normal circumstances.
The problem is that many of us are overly stressed these days, meaning our bodies are in a constant state of elevated cortisol levels, and this is where it gets problematic in terms of ill health.
Why Elevated Cortisol Is Bad News
There are lots of reasons why raised cortisol is not good news for your health, but I want to stay focused by discussing those relating to weight gain in this article.
1. Blood Sugars and Diabetes
When you are under stress, cortisol provides the body with glucose (by using gluconeogenesis in the liver) to tap into your protein stores.
As we’ve already seen, this energy is there to help in a fight or flight situation.
The problem is when you have elevated cortisol levels your blood sugars remain high, because cortisol inhibits insulin’s effect, making your insulin resistant. This is bad, because the high sugars in your blood aren’t being dealt with, yet the body continues to pump out insulin, which you are now resistant to.
It could be represented very simplistically like this;
Eventually the pancreas will struggle to meet this high demand for insulin, glucose levels in the blood will remain high, and so this unhealthy cycle continues.
Theoretically speaking, this can increase your chance of becoming type 2 diabetic.
2. Weight Gain and Obesity
If your cortisol levels are repeatedly elevated, studies show this can lead to weight gain;
Central fat distribution is related to greater psychological vulnerability to stress and cortisol reactivity… stress-induced cortisol secretion may contribute to central fat and demonstrate a link between psychological stress and risk for disease.
How? Well, cortisol can take triglycerides from storage and relocate them to visceral fat cells (deep in the abdomen).
This is bad, because visceral fat cells have more cortisol receptors than subcutaneous fat, so greater amounts of cortisol is produced as a result. This further adds insult to injury.
A second way in which cortisol may be involved in weight gain, is related to insulin.
If you have high blood glucose levels and insulin suppression (due to high cortisol), your cells are being starved of the glucose they need. So, hunger signals are sent to the brain, causing you to eat more, perpetuating the situation.
Of course, unused glucose, which can’t make it’s way into the cells, is eventually stored as body fat.
On top of all of this, cortisol is thought to have an effect on appetite and cravings for high-calorie foods, particularly in women;
These results suggest that psychophysiological response to stress may influence subsequent eating behavior. Over time, these alterations could impact both weight and health.
How Cortisol Can Help Burn Fat
So, bringing this fullcircle, what has the all got to do with our study on “carb back-loading.”
Well, as I’ve mentioned, cortisol gradually builds up overnight, peaking in the morning when you wake up.
This is a natural process, and quite normal.
In fact, it is something you can use to your own advantage.
This is because when cortisol levels are high — without elevated insulin levels or chronic stress — like first thing in the morning, it triggers the breakdown of triglycerides into free fatty acids (FFAs) for metabolization (lipolysis).
That means in the morning, cortisol could actually help you burn fat.
But, your diet must be right, for this to happen.
Don’t Eat Carbs At Breakfast
It appears that eating a high carb breakfast is the worst thing you could do for fat loss, providing all of the necessary ingredients to switch your body from being a natural fat burner, to a sugar burning, fat accumulator.
However, by avoiding the typical breakfast, high in carbs, such as cereal or toast, you can boost your fat burning potential. In essence what this does, is allow cortisol levels to naturally reduce (about 2 hours after waking).
On the other hand, if you eat those morning carbs, you keep your cortisol levels elevated, which is not good for the body.
According to Kiefer, a much better time to eat high carb foods is after a good weight training session. And, this is the premise behind the carb back-loading plan.
Diet and Exercise Plan
In addition to the above, to prevent your cortisol levels getting out of control, and constantly being elevated, there are a number of steps you can take;
- Follow a low glycemic load diet.
- Eliminate trans fats and other unhealthy omega 6 fat sources.
- Eliminate or reduce your caffeine intake (2-3 cups of coffee per day can elevate cortisol levels).
- Drink alcohol in moderation, if at all.
- Eat lots of whole plant foods, such as vegetables, fruits, legumes, nuts, and seeds.
- Get enough omega 3 fats into your diet from oily fish or fish oil supplements.
- Take regular exercise, but do not overtrain.
- Add probiotics to aid gut health.
Also remember that stress reduction, and getting adequate sleep, are extremely important for keeping cortisol levels at bay.
I’d love to hear your thoughts on this idea of eating carbs at night. Please share your thought in the comments below…