If you think that it's just the turkey making you sleepy after your Thanksgiving dinner, think again. You probably just ate too much.

It has long been acceptable to blame our sleepy ‘food coma' state after Thanksgiving dinner on tryptophan, an essential amino-acid needed by the body and found in turkey, the centerpiece of the Thanksgiving dinner. However Kim Sasso, a registered and licensed dietitian at Loyola University Health System, in Illinois, USA, is breaking down the myth by suggesting that it is probably one's overindulgence in turkey, not to mention potatoes, stuffing, and pumpkin pie, that is the real cause of a food coma, not just the tryptophan.

Tryptophan is found in turkey, but it is also found in other meats, as well as yogurt, eggs, fish, and cheese, and in fact higher levels of tryptophan are found in soybeans compared to Thanksgiving turkey, Sasso notes. "Because of transport and breakdown, not enough tryptophan will reach the brain to cause sleepiness after a holiday meal," says Sasso, addressing the popular myth.

However Sasso does ease our guilt at overindulging a little, by revealing that other factors, and not just second helpings, also play a role in contributing to that food coma feeling: "Likely, the stressful hustle and bustle of the holiday, travel schedules, alcohol indulgence and cooking tasks will contribute more to fatigue than a few slices of turkey," she points out.

To help us try and avoid the food coma, and curb the calories, Sasso has revealed her top tips for a healthier Thanksgiving:

- Don't skip your usual meals that day. "Eat breakfast and lunch so you avoid overeating during the traditional Thanksgiving dinner," says Sasso. "If you save your appetite for the big meal, you will likely eat more and experience the 'food coma' many complain about."

- Choose your indulgences carefully. "Focus on eating your favorite once-a-year holiday foods and pass on other everyday dishes," says Sasso, who outlines that overeating appetizers isn't worth it if the main course is the star event for you.

- Focus on quality, not quantity. "Three slices of dessert will not taste as good or be as appreciated as three small sampling portions," she says. Sasso also advises that extras like ice cream or whip cream can be cut out to reduce the overall calorie intake somewhat.

- Fill your plate with vegetables and fruit. "Produce is loaded with vitamins and minerals, and you will benefit from the fiber," says Sasso. "Eating vegetables doused in cream sauce and butter is better than not eating any at all."

The New York Times and Business Insider Australia both estimate that Americans will consume around 2,500 calories during their Thanksgiving dinner if they indulge in all their favorite traditional foods. The US Department of Agriculture recommends adults over the age of 18 consume between 1,800 and 3,200 calories a day depending on age, gender, and activity level.