It’s the one time of the year where you can eat as much as you want and no one will judge you! After you eat your meal you might become tired. Yes, while turkey contains tryptophan, but not in quantities high enough to make you really sleepy. So what really makes you tired? According to The Healthy, it's all the sides which contains fats and carbs, and not to mention the alcohol.
The average festive meal contains 229 grams of fat and 3,000 calories, reported MSNBC; that’s more than most men and women eat in an entire day! Digesting fat requires a lot of energy, so the body sends more blood to your digestive system to manage the load. Reduced blood flow throughout your body means reduced energy.