The thermic effect of food

The Thermic Effect of Food (also known as Dietary Induced Thermogenesis) is the amount of energy expenditure above the basal metabolic rate due to the cost of processing food for use and storage. This basically just means it is the amount of energy it takes for your body to digest, absorb and metabolise the food you eat.

This process makes up a part of your daily energy expenditure (calories out), and it also represents around 10% of healthy adults eating a mixed varied diet’s caloric intake. For example, if you expend 2000 calories in a given day, around 200 of those would be burned from simply eating food.

The same food groups that you’ve heard talked about as being healthier are also the ones higher in their thermic effect. Protein and complex carbs, for example, have a higher thermic effect than fats or simple carbs because your body has to work harder to break them down. This means they spend more energy and burn more calories in the process.

The energy required to digest each macronutrient (its TEF) is measured as a percentage of the energy provided by it.

• Fat provides 9 calories  per gram. Its TEF therefore is 0-5%
• Carbohydrate provides 4 calories per gram. Its TEF is then 5-15%
• Protein provides 4 calories per gram. Its TEF is 20-30%

Looking at the above data, protein tops the list with 20-30% of the calories you consume from protein being used to digest and metabolise it.

So what we have found out is that a high protein diet has a metabolic advantage over normal or low protein diets with the same amount of caloric intake. This diet has also been proven to keep you full for longer.

The next macronutrient to discuss is carbohydrates. They have the next most thermic effect with a TEF of 5-15% based on the the carbohydrate source. High fibre carbohydrates have a higher thermic response and digest more slowly, allowing you to be full for the whole day. Low fibre alternatives have less effect and are proven to keep you full for less long.

An interesting study from 2017 found that participants increased their metabolism by more than 92 calories a day by just substituting refined grains for whole grain alternatives. That’s a lot!

Dietary Fats are shown to have the lowest thermic effect at 0-5% and it is because they are the simplest to digest. This doesn’t mean you should exclude fats from your diet entirely, but it does mean you need to choose the right ones. Fats play a vital role in many bodily functions like protecting organs, helping maintain body temperature and more, so they are definitely worth keeping around. Just in a safer way.

Good sources of fats that can be included in your diet are: avocado, salmon, nuts, egg yolks or pumpkin seeds.

The “Quick Fix” Diet

You may have heard about low carb, or low fat diets for weight loss, but restricting food groups in this way isn’t sustainable and won’t work in the long term.

Your body compensates for the calorie deficit by slowing down your metabolism and holding on to every calorie you consume, storing them as fat.

So the better way forward is to aim for a healthy and balanced calorie deficit including protein rich foods, complex carbs and the right dietary fats. These food groups with a higher thermic effect will have your body working hard so you can lose weight in a healthier manner.