Understanding the thermic effect of food

Did you know, you can burn more calories just by eating certain foods? In the same way that a high intensity workout (HIIT) burns more calories after exercise compared to steady-state cardio, some food types can have an increased afterburn too, because of the energy it takes for your body to break it down.

This is called the thermic effect of food, with certain food types increasing metabolic rate after ingestion. In this blog, we explain how eating more metabolism-boosting foods with a higher thermic effect can help fast-track your health and fitness goals.

What is the thermic effect of food?

The thermic effect of food (TEF) is the amount of energy it takes for your body to digest, absorb, and metabolise the food you eat.

TEF makes up a part of your daily calorie expenditure (calories out), and usually represents about 10% of the caloric intake of healthy adults eating a mixed and balanced diet. So for example, if you expend 2000 calories in a day, around 200 of those will be burned just from eating food.

Certain food types such as protein and complex carbs have a higher thermic effect than fats or simple carbs because your body has to work harder to break it down, thus spending more energy and burning more calories.

Varying factors affect TEF, primarily the portion size of your meal and its macronutrient composition – protein, carbohydrates and fats – along with your age.

Understanding the thermic effect of food and how it impacts your metabolism is just the first step towards achieving your health and fitness goals. At Revolution, we go above and beyond industry standard Personal Training. We provide comprehensive nutritional guidance tailored to your unique needs and goals. Curious about how your diet can fuel your body more effectively? Why not take the first step towards a healthier, fitter you? Sign up for a free taster session today. You'll get a taste of our high-intensity workouts and receive personalized nutritional advice that will help you maximize the thermic effect of your diet. Remember, the right nutrition is just as important as the right exercise. Let us guide you on your journey to optimal health and fitness.

How do macronutrients alter the thermic effect of food?

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

So that means protein tops the charts as the most thermic macronutrient, with approximately 25-30% of the calories you consume from protein being used for digestion and metabolism.

This is why a high protein diet has a metabolic advantage over normal or low protein diets with the same amount of total calories and has been proven to keep you fuller for longer.

Top tip: If you find yourself hungry soon after breakfast try swapping your cereal for protein-rich eggs and oily fish to fire up your metabolism and keep your blood sugar on a level to avoid the mid-morning crash.

Carbohydrates are the next most thermic macronutrient, with a TEF of 5-15% depending on the carb source. There’s a reason we recommend complex carbs on our nutrition plans to give you sustained energy for your personal training sessions and throughout the day.

High fibre carbs digest more slowly and have a higher thermic response, packing in more nutrients and vitamins along the way.

Choosing wholegrain rice, pasta and bread over refined white variations where the vitamin-rich bran and germ are removed will keep you fuller for longer by reducing blood sugar spikes (and the hunger pang / energy crash that follows them) after meals.  

A 2017 study found participants increased their metabolism by more than 92 calories per day just by substituting refined grains for whole grains. Just sayin’!

Top tip: Swap your baked white potato with beans and cheese for a sweet one topped with tuna for an energising lunch that doesn’t bring the 3pm slump.

Dietary fats have the lowest thermic effect at approximately 5-10% and are the simplest to digest. That doesn’t mean you shouldn’t include fats in your diet – it’s just a case of choosing the right ones.

Fats play a vital role in maintaining healthy skin, hair and nails, protecting vital organs against shock and helping maintain body temperature. They can also be used as an energy source, and slow down the body’s insulin response to high sugar foods.

Good sources of fat to include in your diet are avocado, salmon, nuts, egg yolks and pumpkin seeds.

Top tip: Swap vegetable cooking oil with olive or coconut oil for a healthier fat alternative.

Read more about the different macronutrients and why they’re important on our blog, and see 5 easy everyday swaps you can do today.

Why is the thermic effect of food so important?

If you’re looking to lose body fat or build muscle it’s important to understand the thermic effects of protein and other food groups and how they work to fuel your body.

When we overeat we’re least likely to store excess calories from protein due to the higher thermic effect, followed by carbohydrates, and lastly dietary fats. This is another reason why protein is incredibly important in weight regulation. Try to hit at least 1.8g of protein per kg of body weight, as part of a balanced diet with plenty of whole foods and vegetables to help you reach your goals.

Don’t fall into the quick fix trap!

Trying low carb or low fat diets for weight loss may be tempting, but cutting or restricting food groups in this way just isn’t sustainable and won’t work in the long term.

Your body compensates for the calorie deficit by slowing down your metabolism and clinging on to each and every calorie you put into it, storing as fat.  

So the trick is to put yourself in a *healthy* and balanced calorie deficit for longterm sustainable results. Including more protein-rich foods (at the right time) with a higher thermic effect (i.e. lean meat, fish, eggs and legumes) will keep your body working hard so you can bask in the afterburn long into your day.

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