This question has surely crossed your mind at one point or another. Likely, you’ve heard at least one time that carbs at night do indeed make you fat. But does this statement have any scientific credence to it? Is it true that the reason you can’t lose weight is because you like to eat late at night? Let’s try to analyze and answer these questions with science and bad humor.
Where does this seemingly universally accepted statement come from anyway?
I have no idea. I think most people who cling to this statement have just heard this phrase their whole life so they just stick to it. Those who defend this notion, that eating carbs at night make you fat, will usually point out that since you are about to go to sleep, your metabolism will slow down and all those carbs will be automatically converted to fat. Conversely, they’ll likely argue that if all your carbs are eaten early in the day, you will have the opportunity to magically burn those carbohydrates in your super active daytime lifestyle (that was sarcastic, most of our jobs are probably mostly sedentary, i.e. desk jobs).
So what REALLY happens to our metabolism when we sleep?
It seems logical to think that while our body’s are still, they’re metabolically inactive. At the very least, our body’s metabolism must be significantly less than it is during the day, right? Well, it’s not that simple. Research done on resting basal metabolic rate compared to sleeping metabolic rate has shown some interesting results. Here are three findings relevant to our discussion:
- Averages done on the resting metabolic rate (RMR) and sleeping metabolic rate (SMR) proved to be SIMILAR and NOT SIGNIFICANTLY DIFFERENT. [5,7]
- Sleeping metabolic rate was directly correlated with body mass index. Obese individuals had a SMR LOWER than their RMR. Non-obese individuals had a SMR HIGHER than their RMR. So if you’re not obese, you’re actually burning more calorie while sleeping than you are playing Playstation. 
- Exercise INCREASES sleeping metabolic rate significantly, which leads to greater fat oxidation (breaking down fat for energy). 
So, it doesn’t really seem like our bodies are metabolically inactive during sleep after all. In fact, we might even be burning more calories during sleep than we are at rest during the day.
What about the idea of using morning carbs for energy?
I touched on this idea in my post on intermittent fasting, but let’s take another look. Having carbohydrates in the morning for energy is more subjective than we are lead to believe. Many people, including myself, are big supporters of the idea that being in a fasted state in the morning does not equal a decrease in performance. Speaking from personal experience, I have attended class, studied, and performed my day to day activities just fine in a fasted state (note: I would consume black coffee on those days). With that said, there are certain occasions in which I did notice a decrease in performance without my morning carbohydrates for fuel: examinations and weight lifting. I wouldn’t recommend anyone about to embark on a tough examination to go in on an empty stomach. It makes sense too, during an examination we need to think more critically than usual and need mental endurance to brace ourselves to complete the examination without collapsing. Several studies have shown the benefits of having breakfast on school performance as well (granted, they’re usually performed on children and adolescents) . The ingestion of carbohydrates for athletic performance is a lot more physiologically obvious and heavily supported by evidence .
So do carbs at night make me fat or not?
The reason you may be having a hard time losing weight is REALLY unlikely due to you eating carbs at night. A randomized controlled study taken place over 6 months was done to give a good answer to this question. This study put one group of police officers in an experimental group of subjects having majority of their carbohydrates (approximately 80%) at night and the control group having majority of their carbohydrates throughout the day. Both groups consumed the same amount of calories, proteins, carbohydrates, and fat each day. After 6 months, the experimental group (who consumed their carbs at night) lost significantly more weight and body fat then the control group . So yeah, feel free to reference that study to the next person about to choke you out for grabbing a slice of toast at 10pm.
2-Chainz…I mean terrible music…I mean 2 random thoughts…
- I’m not here to say that eating carbohydrates at night is an amazing idea, it’s just not a terrible one. In fact, eating RIGHT before going to sleep is probably not a great idea and will probably leave you feeling bloated in the morning. Give your food some time to digest before hitting the sack (while typing those last three words, I just realized what an awkward phrase that is to reference going to sleep. Seriously, who thought of that?).
- Carbs at night may improve sleep. Again, not too late, but this study looked at carbohydrates consumed 4 hours before sleep and showed improvement in sleep. 
- Sorry for the late post.
- That’s 3 random thoughts, bro. You’re ability to count in sequential numerical order is as good as 2-chainz’ ability to make music.
If you will notice, my conclusions are usually pretty similar. Super restrictive rules that are spread around by society and taken as facts, are usually far from factual. In an all too familiar pattern, the big picture, which is the most important aspect to weight loss, is skipped over. Are you taking in more calories than you are consuming? Are you balancing out your macronutrients in such a fashion to optimize weight loss? The best take away you could take from this article is to go back to putting the focus on the TOTAL quantity/quality of calories consumed in a day. Don’t put the blame on your lack or weight loss on having to eating dinner later than your friends are. Instead, focus on exercising more, eating less, eating higher quality/nutrient dense foods, and indulging on the occasional slice of chocolate cake to maintain your sanity.
- Afaghi A, O’connor H, Chow CM. High-glycemic-index carbohydrate meals shorten sleep onset. Am J Clin Nutr. 2007;85(2):426-30.
- Hodgkin, G. Nutrition and Academic Achievement: Are They Related? An International Journal of Faith, Thought, and Action. http://dialogue.adventist.org/articles/20_1_hodgkin_e.htm. Accessed February 16, 2015.
- Mischler I, Vermorel M, Montaurier C, Mounier R, Pialoux V, Pequignot JM, Cottet-Emard JM, Coudert J, Fellmann N. Prolonged daytime exercise repeated over 4 days increases sleeping heart rate and metabolic rate. Can J Appl Physiol. 2003 Aug;28(4):616-29
- Norton, L. “Carbs at Night: Fat Loss Killer or Invisible Boogey Man?” Available at: http://www.bodybuilding.com/fun/carbs-at-night-fat-loss-killer-or-imaginary-boogeyman.html. Accessed February 16, 2015.
- Seale JL, Conway JM. Relationship between overnight energy expenditure and BMR measured in a room-sized calorimeter. Eur J Clin Nutr. 1999 Feb;53(2):107-11.
- Sofer S, Eliraz A, Kaplan S, Voet H, Fink G, Kima T, Madar Z. Greater weight loss and hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner. Obesity (Silver Spring). 2011 Oct;19(10):2006-14.
- Zhang K, Sun M, Werner P, Kovera AJ, Albu J, Pi-Sunyer FX, Boozer CN. Sleeping metabolic rate in relation to body mass index and body composition. Int J Obes Relat Metab Disord. 2002 Mar;26(3):376-83.
- Available at: http://www.fao.org/docrep/w8079e/w8079e0n.htm. Accessed February 16, 2015.