By Dayne Hudson
We all know the feeling.
We eat a big meal that contains a lot of carbohydrates (think a large hamburger and chips followed by a large sugary desert) and all of sudden.....we hit the wall.
It's a common question, why do carbs make me sleepy?
It's quite a complex series of events within your body but when explained in these steps, will make perfect sense.
WHY DO I GET TIRED AFTER A HIGH CARB MEAL?
STEP ONE: You consume a whole heap of carbohyrates, which triggers a large insulin release.
STEP TWO: The insulin results in the uptake of the BCAAs, but NOT tryptophan (an essential amino acid) into your muscle which pumps up the ratio of tryptophan to BCAAs in your blood.
STEP THREE: With reduced competition now between BCAAS and tryptophan for transport - the tryptophan is then pumped across the blood brain barrier into the cerebrospinal fluid (fluid in the brain and spine) (1,2).
STEP FOUR: Now that the tryptophan is in the cerebrospinal fluid, it's converted into serotonin (3,4).
STEP FIVE: The serotonin is now metabolised into melatonin courtesy of your pineal gland (5), also found in the brain. Melatonin is associated with sleep onset.
So there we have it!
A meal packed full of carbohydrates, via an indirect mechanism, triggers that post meal sleepiness you've come to experience time and again, thanks to the increase of melatonin in the brain which we know causes tiredness (6).
Not really what we want is it?
ARE CARBS BAD?
As I've told you 100 times in many articles via this website - absolutely NOT.
For a full breakdown of WHY - check out this article NOW - insulin DOES NOT cause fat gain!
WHEN IS THE BEST TIME TO EAT CARBS?
There is no BEST or WORST time - if you're training regulary or even if you've just started, research has found that you'll most likely increase your sleeping metabolic rate (7).
The above cited study was done on eleven young untrained men, who exercised at moderate intensity 5 hours a day for 4 days.
This means you'll still be burning calories at a steady rate when you're asleep.
Other research shows there's no difference between our resting metabolic rate during the day and your sleeping metabolic rate at night (8,9).
So what harm will carbs do if we eat them before bed?
Well, nothing.
We might be burning more calories when we're asleep, or THE SAME AMOUNT as when we're awake, as evident in the studies above (8,9).
CARBS AREN'T BAD BEFORE BED
It's about overall energy balance - are you expending more energy then you consume?
The myth of carbs not being "burnt off" before sleep resulting in more body fat is a good theory, but not supported by science.
So get stuck into the carbs - just not too much that you find yourself asleep!
"Stay Fit, Stay Flexed!"
REFERENCES
(1) Pardridge WM, Oldendorf WH (1975). "Kinetic analysis of blood–brain barrier transport of amino acids". Biochim. Biophys. Acta 401 (1): 128–36.
(2) Maher TJ, Glaeser BS, Wurtman RJ (1984). "Diurnal variations in plasma concentrations of basic and neutral amino acids and in red cell concentrations of aspartate and glutamate: effects of dietary protein intake". Am. J. Clin. Nutr. 39 (5): 722–9.
(3) Fernstrom JD, Wurtman RJ (1971). "Brain serotonin content: increase following ingestion of carbohydrate diet". Science 174 (4013): 1023–5.
(4) Wurtman RJ, Wurtman JJ, Regan MM, McDermott JM, Tsay RH, Breu JJ (2003). "Effects of normal meals rich in carbohydrates or proteins in plasma tryptophan and tyrosine rations. Am. J. Clin. Nutr. 77 (1): 128–32.
(5) Wurtman RJ, Anton-Tay F (1969). "The mammalian pineal as a neuroendocrine transducer." Recent Prog. Horm. Res. 25: 493–522.
(6) Afaghi A, O'Connor H, Chow CM (2007). "High-glycemic-index carbohydrate meals shorten sleep onset." Am. J. Clin. Nutr. 85 (2): 426–30.
(7) 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.
(8) 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.
(9) 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.
