Sleepy After Eating A Big Meal? Here's Why

11/22/2012 02:45 am ET

Calories give us energy, so why do big meals make us sleepy? This counterintuitive experience is a common one, and that goes double on Thanksgiving, where the average American packs up to 3,500 calories in a single meal. And while many people blame the turkey's tryptophan for their soporific state, the truth is that other foods -- like cheese and eggs -- have just as much of the sleep inducing amino acid.

So what gives? It turns out that a few factors conspire to make the Thanksgiving meal the sleepiest yet.

First of all, if you've traveled for the holidays, shifts in your schedule, stress or even slight jet lag can take their toll regardless of what you're eating. But, add to that a few hormonal shifts that happen in the body after a chow down, and you've got a recipe for food coma.

For one, high-carb, high-fat and high-sugar foods (like, say, buttery mashed potatoes and pumpkin pie) trigger a neural response as soon as they hit the small intestine, explains Scientific American. That response, in what's called the parasympathetic nervous system, tells our body to slow down and focus on digesting rather than go out and seek more food.

More specifically, researchers found, a group of brain cells called orexin neurons that are found in the hypothalmus are very sensitive to glucose levels, which spike after a big meal. Those neurons produce a protein, orexin, which moderates wakefulness in the brain.

But orexin isn't the only sleep-related neurohormone affected by food. As the quantity of food increases, so too does the amount of insulin released as a normal part of the body's digestion. The insulin, in turn, increases the amount of seratonin and melatonin that flood the brain, two chemicals associated with drowsiness (and, for that matter, happiness).

While there's no way to avoid a sleep response to a big meal (other than reducing the overall amount you eat and lowering fat, refined carbohydrate and sugar in the first place), it isn't dangerous or a sign of a greater health problem.

It's important to note that having a big meal can affect the important rest you need later in the evening. That's particularly true for those who eat late -- as often happens during a celebratory meal like Thanksgiving.

As Dr. Loren Greene, a clinical associate professor in the Endocrinology Division of the Department of Medicine at NYU previously explained to HuffPost Healthy Living, "If you eat a late dinner, say 10 p.m. with a dessert, some times you start putting out insulin in the middle of the night which can cause your blood sugar to peak and drop," Greene says. That, in turn, can disrupt the sleep cycle, waking you in the middle of the night or preventing one of the deeper sleep cycles we require for true restfulness.

The moral of the story? Eat early, eat smart and try to get yourself back on your normal eating and sleeping schedule as soon as possible.

Here's more on myths about the Thanksgiving meal:

Thanksgiving Nutrition Myths

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