Diet Linked to Daytime Sleepiness and Alertness in Healthy Adults

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May 7, 2013 — A new study suggests that your level of sleepiness or alertness during the day may be related to the type of food that you eat.

Results show that higher fat consumption was associated with increased objective daytime sleepiness, while higher carbohydrate intake was associated with increased alertness. There was no relationship between protein consumption and sleepiness or alertness. These findings were independent of the subjects' gender, age, and body mass index as well as the total amount of sleep they were getting and their total caloric intake.

"Increased fat consumption has an acute adverse effect on alertness of otherwise healthy, non-obese adults," said principal investigator Alexandros Vgontzas, MD, professor of psychiatry at the Penn State College of Medicine in Hershey, Pa.

The research abstract was published recently in an online supplement of the journal SLEEP, and Vgontzas will present the findings Tuesday, June 4, in Baltimore, Md., at SLEEP 2013, the 27th annual meeting of the Associated Professional Sleep Societies LLC.

The study group comprised 31 healthy, non-obese normal sleepers without sleep apnea, ranging in age from 18-65 years, who spent four consecutive nights in a sleep lab. On the fourth day objective sleepiness was assessed with the Multiple Sleep Latency Test (MSLT), and meals were provided five times to assess diet.

According to the authors, previous studies had found that diet composition affects subjective sleepiness. The current study adds to this body of research by showing a similar association between diet and objective sleepiness.

"Excessive daytime sleepiness and fatigue are very prevalent in the modern world and on the rise," said Vgontzas. "It appears that a diet high in fat decreases alertness acutely, and this may have an impact on an individual's ability to function and also public safety."

Well I'm the exception to that one!!!! When I ate carbs, I always needed an afternoon nap and was always lethargic. Now I'm high fat, low carb, I'm unstoppable lol!!!!

Jo xxx

Same here. High carb made me not only "objectively" sleepier, but "actually" sleepier. If the opportunity presented itself I always wanted a nap. Really can't sleep during the day now on a low carb higher fat diet.

I also find I have more energy with LC eating, but I do sleep better at night. Probably because I do more during the day and no heartburn.

Only a 4 day study with 31 subjects and they didn't bother to specify what else they ate. It will likely make mainstream news anyways before peer review and publication because it disses FAT.

BTW: Nodding off during the days is a thing of the past now for me too, even after a poor nights sleep as long as I stay off the carbs.

I wonder if it is because they're not adapted to run off of fat like most of us are.
Here's Dr. Briffa's rebuttal:
Do low-carb diets really make people sleepy?

I'm guessing the folks in this study are equating high fat with onion rings (as shown in the accompanying photo) and desserts. They do this time after time. Try giving the subjects a tablespoon of coconut oil....bet they're not dozing off then.

What a load of bilge. One of the first, and most marked, effects of my low carb life was the lack of the Near-Coma-After-Lunch-Syndrome.

yeah...eat fries and a burger at lunch, and it's about the same as taking sleeping pills for me. Sugarcarbcrap makes me sleepy. Fat does not.

Exactly. I looked at the link but wasn't able to find the complete study to read. Wonder if they had cake, cookies, fries, etc. No wonder they were sleepy! Many low carb eaters struggle to get enough fat right after they lower carb intake because we are so used to eating butter - with bread. Or potato chips or whatever.So not unreasonable to assume they were high fat/high carb foods. Also agree that it is a very small number of subjects and if I read it right, they only tested the diet connection on day 4. Someone correct me if I misunderstood.

Anyway, this is not even a blip on the radar of nutrition IMHO.

This article is just the opposite from reality. When I ate carbs it almost put me in a coma protein had no effect at all.

It is annoying that the study cannot be found for review. To me, it sounds like basically a four or five day study. If that is true, and assuming it was a clean high fat diet like one that would move test subjects into ketosis, then I would say its more akin to "Atkins flu" type sleepiness. what a ridiculous waste of research money.

A commenter on Dr Briffa's post about it found the abstract, at least. It's in this huge 489 page PDF file (just to warn you before you click):
http://www.journalsleep.org/Resourc...tSupplement.pdf
It’s on page A335, abstract number 0977. And as Dr Briffa said, has very little merit at all, as it's epidemiological, not even a proper clinical study.

The article is utter nonsense. I've never had so much energy in my life and I'm sixty-freaking-three. And, yes, a spoonful of coconut oil is like getting a shot of adrenaline. It makes me so sad for those people who will believe this misleading report and won't realize there is a distinction between the word "fat" being used to describe onion rings and French fries as opposed to "fat" meaning butter, coconut oil, and unprocessed meat.

The carbs in the low-carb diet - but not the high-carb diet - must be wheat.