The thermic effect of food (TEF) refers to the increase in metabolic rate that occurs after consuming food. When we eat, our bodies expend energy to digest, absorb, and store the nutrients from the food. This energy expenditure contributes to the overall calories burned by the body.
Understanding the TEF is beneficial for weight management and optimizing our metabolism. By consuming certain foods that have a higher thermic effect, we can enhance our body's calorie-burning potential. In this comprehensive guide, we will explore the science behind the thermic effect of food, the role of macronutrients, and how we can utilize this knowledge to achieve our health and fitness goals.
What is the Thermic Effect of Food?
The thermic effect of food is the energy expenditure required for the digestion, absorption, and metabolism of the food we consume. It accounts for approximately 10-15% of our total energy expenditure or TEE. [1]
The thermogenic effect of food, or diet induced thermogenic, is generally considered to be the smallest percentage of total energy expenditure. Following basal metabolic rate at 60% and physical activity at 25-30%, which is broken down into NEAT (none exercise related thermogenesis AKA normal movement) and actual deliberate exercise.
The exact value of TEF varies from person to person and is influenced by factors such as age, gender, and body composition. When we eat, our bodies go through a series of processes to break down the food into its basic components. [2] This involves mechanical digestion in the mouth, chemical digestion in the stomach and intestines, and absorption of nutrients into the bloodstream. Each step requires energy, which contributes to the overall TEF.
The Role of Macronutrients in the Thermic Effect of Food
The macronutrients in our diet - protein, carbohydrates, and fats - have different effects on the thermic effect of food. Research has shown that protein has the highest thermic effect, followed by carbohydrates, and then fats. [3]
Protein and the Thermic Effect of Food
Protein has the highest thermic effect among the macronutrients. It requires more energy to digest, absorb, and metabolize compared to carbohydrates and fats. Studies have shown that protein has a thermic effect of around 20-30%. This means that if you consume 100 calories of protein, approximately 20-30 calories will be burned during digestion and metabolism. [4]
In addition to its high thermic effect, protein is also known to increase satiety and reduce appetite. This can be beneficial for weight management, as it helps to control calorie intake and prevent overeating. Including adequate protein in your diet can also help preserve lean muscle mass during weight loss.
Carbohydrates and the Thermic Effect of Food
Carbohydrates have a moderate thermic effect compared to protein. The thermic effect of carbohydrates ranges from 5-15%. This means that if you consume 100 calories of carbohydrates, approximately 5-15 calories will be burned during digestion and metabolism. [6]
The thermic effect of carbohydrates can vary depending on the type and complexity of the carbohydrates consumed.
The Thermic Effect Of Fiber
A lot of people don't actually count fiber as a macro, but for the purposes of this article it makes sense that we include it. Foods high in fiber, such as whole grains, fruits, and vegetables, tend to have a higher thermic effect compared to refined carbohydrates. This is because the body needs to work harder to break down and absorb the fiber-rich foods. We don’t get many or any calories from fibers depending on whether it’s soluble or not, so in many cases it’s realistically just filling you up. [6]
Currently the FDA estimates you get something around 1-2 calories per gram of fiber, but other countries have this number as lower.
Fats and the Thermic Effect of Food
Fats have the lowest thermic effect among the macronutrients. The thermic effect of fats ranges from 0-5%. This means that if you consume 100 calories of fats, approximately 0-5 calories will be burned during digestion and metabolism. [7]
Although fats have a lower thermic effect, and higher calorie per gram ratio, they still play an important role in our diet. Fats provide essential fatty acids, help absorb fat-soluble vitamins, and contribute to the taste and texture of foods. Choosing "healthy fats", such as those found in avocados, nuts, and olive oil, can provide additional health benefits while keeping the overall calorie intake in check. We can also seperate fats down into further subcatogies, and the thermic effect does vary.
The Thermic Effect Of Alcohol
Yes, that’s right alcohol has it’s own thermic effect, it’s actually very similar to protein at 22.5%, but before you rejoice and think that technically your drink has less calories, there’s something you should know. Because Alcohol is a toxin, your body always choses to process that first. [8]
Meaning that it will convert any calories that you have from say protein, that you wanted to use to retain muscle into the body’s fat stores. So, whilst Alcohol may have a high thermic effect it will completely derail any plans you had around a balanced diet.
What Are The Thermic Effects Of Each Macro?
- Fiber – Fiber is somewhere between 1-2 calories per gram. It’s thermic effect is also up for debate with some studies showing it to be around .9 calories per gram, and others showing it to be negligible.
- Alcohol – It has around 7-8 calories per gram of pure alcohol with a thermic effect of 22.5%
- Fat – Fat provides a whopping 9 calories per gram with the lowest thermic effect of 0-5%
- Carbohydrate – Carbs provide 4 calories per gram with a middle range thermic effect of 5-15%
- Protein – Protein provides 4 calories per gram with a thermic effect of 20-30% making it second only to fiber.
Factors Influencing the Thermic Effect of Food
Several factors can influence the thermic effect of food, apart from macronutrient composition. Let's take a closer look at these factors:
Meal Size Effects Thermogenesis
The size of your meal can affect the thermic effect of food. Research suggests that larger meals tend to have a higher thermic effect compared to smaller meals. This may be due to the increased workload on the digestive system when processing a larger amount of food. [9] This applied to large meals as well as simply larger low calorie foods. [10]
However, it's important to note that portion control is still crucial for weight management. While larger meals may have a higher thermic effect, consuming excessive calories can still lead to weight gain. [11] It's essential to find a balance between meal size and overall calorie intake. Which is why we generally recommend high volume low calorie foods as a the best option for bulking out your meal size as a way to eat more volume without having the downside of too many calories.
This means that in and of themselves foods that are low in calories actually have a doubling effect of assisting a diet, in that they help you feel full, whilst actually requiring more calories to process, think foods like cauliflower and spinach. [12]
With 1lb of spinach being around 100 calories, and cauliflower being similar.
It is also ideal for muscle retention and growth to eat 4 or 5 times a day consuming protein, so using large low calorie foods to fill out meals is the most effective method to retain the benefits of both frequent meals and thermogenis from meal size.
Meal Composition
In addition to macronutrients, other components of a meal can influence the thermic effect of food. For example, spices such as chili peppers and caffeine have been found to slightly increase metabolism and enhance the thermic effect. However, the effects of these substances are generally minor and short-lasting, but have shown some results in trials for weight loss. [13.14]
Choosing whole, unprocessed foods that are high in fiber can also increase the thermic effect of food. Fiber requires more energy to digest and helps promote feelings of fullness. Including fruits, vegetables, whole grains, and legumes in your diet can enhance the thermic effect and support weight management.
Age and Metabolism
Age can impact the thermic effect of food and overall metabolism. As we get older, our metabolic rate tends to decrease, including the thermic effect of food. This reduction in metabolism is partly due to a decline in muscle mass and hormonal changes. [15]
However, regular physical activity can help offset the age-related decline in metabolism. Exercise, particularly strength training, can help build and maintain muscle mass, which can increase the thermic effect of food and overall calorie burn.
Insulin Resistance and Obesity
Insulin resistance, a condition where cells become less responsive to insulin, can affect the thermic effect of food. People with insulin resistance, often associated with obesity and type 2 diabetes, may have a reduced thermic effect compared to those without insulin resistance. Whilst this is a widely accepted theory there are some recent conflicting studies [16, 17]
Managing insulin resistance through a balanced diet, regular exercise, and weight loss, if necessary, can help improve the thermic effect of food and overall metabolic health.
Exercise Increases The Thermic Effect Of Food
It's important to note that this effect is separate to your metabolism going up as a result of training. Your body actually burns carbohydrates specifically faster after exercise. In trying to utilize the energy faster it converts it faster, thus using more calories to burn the calories you've consumed faster. [18] In terms of making the most of the calories this is technically "inefficient" which is why the body doesn't do it by default. However, in terms of weight loss this is an extra benefit.
Not All Macros Are Created Equal The Thermic Effect Of Different Protein Sources
This is where things are probably going to get a bit too nitty gritty for most people looking to use the thermic effect of foods, but it's interesting none the less. Generally speaking, it's considered that plant proteins are harder for the body to break down, which would suggest a higher thermic effect. [19,20]
And the trade off was considered to be that they were less anabolic in general [21] meaning that they were less effective for building muscle, due to lacking specific amino acids which assist in the muscle building process.
But, even among this conventional set wisdom, there's a whole heap of variables, for example, a recent study showed that whey protein actually had a higher thermic effect than soy protein. [22] In reality, this means it's probably not worth getting too caught up in the exact protein, but it is worth noting that there is variance even within macro nutrients.
Harnessing the Thermic Effect of Food for Weight Loss
Understanding the thermic effect of food can be a valuable tool for weight loss and maintaining a healthy metabolism. Here are some practical tips to harness the thermic effect of food:
Prioritize Protein
Including adequate protein in your diet is essential for maximizing the thermic effect of food. Aim to include lean sources of protein such as chicken, fish, tofu, and legumes in your meals. Protein not only has a high thermic effect but also helps increase satiety and preserve lean muscle mass.
Choose Fiber-Rich Foods
Fiber-rich foods, such as fruits, vegetables, whole grains, and legumes, can enhance the thermic effect of food. These foods require more energy to digest and can help you feel fuller for longer. Incorporate a variety of fiber-rich foods into your meals and snacks to support weight management.
Be Mindful of Portion Sizes
While the thermic effect of food can help increase calorie burn, portion control is still essential for weight loss. So go for large, but low-calorie foods. Pay attention to your portion sizes and listen to your body's hunger and fullness cues. Avoid overeating, even if the food has a high thermic effect, as excess calories can still lead to weight gain, meaning you should aim to be in a calorie deficit first, and think of diet induced thermogenesis as a bonus.
Stay Active
Regular physical activity is crucial for maintaining a healthy metabolism and maximizing the thermic effect of food. Aim for a combination of cardiovascular exercise and strength training to boost calorie burn and preserve muscle mass. Find activities that you enjoy and make them a part of your daily routine.
Seek Professional Guidance
If you're struggling with weight loss or want to optimize your metabolism, consider seeking guidance from a healthcare professional or registered dietitian. They can provide personalized recommendations based on your individual needs and goals.
What Is The Thermic Effect Of Food Conclusion
The thermic effect of food plays a significant role in our metabolism and weight management. By understanding the impact of macronutrients, meal composition, and other factors, we can harness the thermic effect of food to support our health and fitness goals. Prioritizing protein, choosing fiber-rich foods, controlling portion sizes, staying active, and seeking professional guidance can all contribute to maximizing the thermic effect and achieving a healthier, more balanced lifestyle. Remember, every small step counts on the journey to optimal health and well-being.
References
1 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6058072/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC524030/
3 - https://pubmed.ncbi.nlm.nih.gov/15466943/
4 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7539343/
5 - https://pubmed.ncbi.nlm.nih.gov/12507635/
6 - https://pubmed.ncbi.nlm.nih.gov/3032832/
7 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3735822/
8 - https://pubmed.ncbi.nlm.nih.gov/2121268/
9 - https://pubmed.ncbi.nlm.nih.gov/1951147/
10 - https://pubmed.ncbi.nlm.nih.gov/31021710/
11 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105579/
12 - https://www.ncbi.nlm.nih.gov/books/NBK221839/
13 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5426284/
14 - https://pubmed.ncbi.nlm.nih.gov/30335479/
15 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4366678/
16 - https://pubmed.ncbi.nlm.nih.gov/16538009/
17 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4115362/
18 - https://pubmed.ncbi.nlm.nih.gov/14669938/
19 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10222455
20 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760812/
21 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6723444/
22 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3500733/
