Total Daily Energy Expenditure (TDEE)

A fundamental principle of nutrition is that body weight change is associated with an imbalance between energy intake and output. On one side, we introduce energy from the food we eat. On the other, we spend energy to maintain life and perform physical work.

With this article, we are going to focus on how the body burns the calories we introduce. This is known as total daily energy expenditure.

What is Total Daily Energy Expenditure?

Every day we consume energy and we burn energy. We consume energy by eating food. We burn energy by maintaining life and performing physical work.

Total daily energy expenditure (TDEE) is the total number of calories we burn in a given day. TDEE is made up of four components:

• Basal metabolic rate
• Thermic effect of feeding
• Exercise activity thermogenesis
• Non-Exercise activity thermogenesis

Basal Metabolic Rate

Basal metabolic rate (BMR) is the energy we need every day to perform basic vital functions. These include breathing, pumping the heart, regulating body temperature, allowing the organs to function, etc.

BMR is the calories we would burn to keep the body alive, at rest, assuming we were laying in bed all day without moving or eating. BMR accounts for about 70% of TDEE making it the main contributor to our daily expenditure.

Interestingly, it's the organs, not the muscles, that use up most of this energy. New muscle mass does increase BMR, but not significantly. This means there isn’t really much we can do to affect BMR. It’s mostly set by genetics.

Thermic Effect of Feeding

Thermic effect of feeding (TEF) is the energy we use in the process of eating, digesting, metabolizing, and storing food. Essentially, we use part of the energy contained in food just to break it down and digest it.

This might sound strange as we eat food to gain energy and not lose it. But metabolically, extracting energy from food comes at a cost. Assuming a balanced diet, TEF accounts for about 10% of TDEE.

TEF is lower during weight loss dieting because, if you eat less food, you won't burn as many calories processing it. In contrast, during weight gain dieting, TEF increases because of higher food intakes.

Exercise Activity Thermogenesis

Exercise activity thermogenesis (EAT) is the energy we use during structured, intentional exercise. It covers all forms of training, including weight training and cardio.

What's intersting about EAT is that we directly control it. We decide how much weight training and cardio to do, so we can influence it substantially. EAT accounts for about 5% of TDEE, but really depends on how much you exercise.

During weight loss dieting EAT descreases. As you lose weight, your mass in reduced and so you naturally need less energy to move your body around. Also the body becomes more efficient and burns less calories to produce the same amount of physical work. The opposite is true during weight gain dieting.

Non-Exercise Activity Thermogenesis

Non-exercise activity thermogenesis (NEAT) is the energy we use for any movement that isn’t purposeful exercise. This includes anything from walking around to doing the chores, maintaining posture, and even fidgeting.

NEAT is incredibly variable. Two individuals of similar body size can have a daily difference of as much as 2000 calories when it comes to NEAT. It generally accounts for about 15% of TDEE, but strongly depends on your activity level.

NEAT is also the biggest contributor to the metabolic adaptations that come with dieting. During weight loss, we tend to feel lethargic and move less causing NEAT to drop. Conversely, during weight gain dieting, the extra calories make us more energic and active.

Contribution to TDEE

The approximate contribution of basal metabolic rate (BMR), thermic effect of feeding (TEF), exercise activity thermogenesis (EAT) and non-exercise activity thermogenesis (NEAT) to total daily energy expenditure (TDEE) in the general population.

Conclusions

Every day, we have some magnitude of resting energy expenditure (BMR) just to stay alive. On top of that, we also do activities of daily living (NEAT), consume food (TEF), and we might also do some structured exercise (EAT).