The Calorie is Not a Calorie – Thermic Effect of Food aka Postprandial Thermogenesis

The Calorie is Not a Calorie – Thermic Effect of Food aka Postprandial Thermogenesis


The box says that 1 cup is 150 Calories. But is it really? Well, not after you eat it!

But Rex, what do you mean?

I’m talking about the thermic effect of food, also known as postprandial thermogenesis, of course!

What the heck is that?

Well, you probably heard that when you eat celery that you’re eating “negative calories.” This is the marketing of people who discovered the thermic effect of food. It’s when your body must use energy to break down, process, digest, absorb, store, and dispose of what you eat and its leftovers. Your body is essentially metabolizing what you ate and burning calories. For example, let’s say you ate a meal of 500 calories. Well, your body requires 50 calories to metabolize that meal and thus the meal is equal to 450 calories.

Does that mean I should eat more?

Unfortunately, no. The formulas in which your total daily energy expenditure somewhat take into account for the thermic effect of food.

Influences and Implications of the Thermic Effect of Food

The reason why I suggest eating a diverse amount of food for each meal is because our digestive system is kicked into overdrive when there is a combination of food that enters our stomach. What are the these factors?

1. The size of the meal

Typically, the larger the meal, the longer the time and more amount of energy your body requires to metabolize the meal. This is why I advocate intermittent fasting. Because your feeding window is shortened, you’re required to eat larger meals to consume the amount of calories that you need.

Kinabo JL, Durnin JV. Thermic effect of food in man: effect of meal composition, and energy content. Br J Nutr. 1990 Jul;64(1):37-44.

Frijoles con Calabaza
2. The composition of the meal

The body expends more energy breaking down protein than it does any other macronutrient. This is why people tend to stay more satiated or fuller when they eat a ton of protein, as opposed to fats and carbohydrates. Also, the variation and complexity of the meal has an effect on the meal. Scientists have also discovered that fat slow the digestion process. This is why you should mix fibers and fats into your meals (make sure you meet your macronutrients, though).

3. The frequency of meals

Experiments have also shown less meal frequency burns more calories. In a study, they gave the same calorie meal on various days, but split up the frequency at which they were eating, and concluded that the body required more energy to burn a single meal than to burn 6 meals displaced across various times.

Tai MM, Castillo P, Pi-Sunyer FX. Meal size and frequency: effect on the thermic effect of food. Am J Clin Nutr. 1991 Nov;54(5):783-7.

4. The pattern at which you eat your meals

Your body adapts to how you eat so by changing up your meal pattern (frequency and timing of meals), the body has a more difficult time burning the calories.

Farshchi HR, Taylor MA, Macdonald IA. Decreased thermic effect of food after an irregular compared with a regular meal pattern in healthy lean women. Int J Obes Relat Metab Disord. 2004 May;28(5):653-60.

5. Your body composition

Naturally, the amount of body fat you have will influence the thermic effect of food. The leaner you are and the more muscle mass you have, the higher the thermic effect of food.

Segal KR, Gutin B, Albu J, Pi-Sunyer FX. Thermic effects of food and exercise in lean and obese men of similar lean body mass. Am J Physiol. 1987 Jan;252(1 Pt 1):E110-7.

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