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It is perfectly safe -- assuming you lead a somewhat healthy lifestyle -- to embrace the gluttony of a Thanksgiving meal, which on average tops 3,000 calories, a full "G" above the daily recommended caloric intake. While that feasting can add an entire pound or two to your heft, it's nothing that a few sessions at the gym can't negate.

So, what about the post-feast crash? Is it the tryptophan that lulls you to sleep? Well, the answer is: sort of.

First, yes, there is tryptophan in turkey. But this essential amino acid, which is broken down to create the feel-good neurotransmitter serotonin, appears in nearly every protein we eat. And turkey has far less of the stuff than some veggies, cheddar cheese, and even cod. (In fact, if you really want to conk out after dinner, swap in eggs for turkey, as they have almost four times more tryptophan than a slice of Tom.)

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Second, realize that no matter what you eat, be it a turkey slice or a deconstructed salad, a lot of blood heads to the gut to tackle digestion. This makes you feel groggy and sleepy because your muscles, lungs, and brain are getting less oxygen than they are used to. This is why it's never a good idea to eat a ton before a strenuous swim.

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But what's knocking you out after you eat is the chemical combination of tryptophan and all those carbs (stuffing, potatoes, sweet potatoes, rolls, pie, wine, etc.). The deluge spikes your insulin level, which to make a very long biochemical story short, ultimately prevents the tryptophan from being broken down, allowing it to travel essentially unchecked to the brain. Put another way: You're getting the purest of pure tryptophan.

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