A breakdown of how your body expends energy. How can we manage calorie burn to our advantage?
On our pursuit to achieve health and fitness goals – whether it be to lose fat, increase muscle, or maintain healthy weight, control of daily calories consumed (energy intake) is critical to the process. We manage this by the quantity, type, and quality of foods we eat. Energy expenditure, or daily calories burned (total daily energy expenditure aka TDEE) is equally as important. We do have some degree of control over calorie burn, so let’s take a closer look at the four key contributing elements of TDEE and understand what we should focus on to gain the most advantage.
Basal metabolic Rate (BMR)* contributes ~70% to total daily energy burn. It represents the number of calories the body consumes at rest to perform essential functions such as breathing, circulation of blood, brain function, temperature regulation, and cell turnover. You burn this energy 24h/day, whether awake or asleep.
Day to day, you cannot influence BMR. The primary factors dictating BMR are height, weight, age, and gender. Smaller people have a lower BMR than larger people. Body composition and hormones also exert influence; leaner individuals have a higher BMR.
Over longer periods of time, BMR can change. As we lose weight our BMR decreases and as we gain weight our BMR increases. However, in the grand scheme we should not look to BMR as a significant factor to manipulate total daily energy expenditure.
Nonexercise Activity Thermogenesis (NEAT) contributes ~15% to total daily energy burn. It represents the number of calories your body consumes through general movement (excluding intentional exercise). Examples include fidgeting, walking around throughout the day, taking the stairs, and running errands.
Daily activity level has an enormous impact on the calories you burn. Studies on people who have sedentary office jobs versus people who have physically strenuous jobs have indicated a 2-3X difference in NEAT – upwards of a 1000 kcal difference per day! It is the main reason why it seems some people can eat more without gaining weight.
Focus on NEAT if you are seeking to lose weight. During a fat loss diet, the most effective and proven way to create a calorie deficit is through reduction in food intake combined with additional movement. Additional calories burned by simply walking around more can be a game changer to maintaining an appropriate calorie deficit. It’s absolutely an element to evaluate if weight loss has stalled – as we continue long enough in a calorie deficit, we are inherently inclined to move around less. NEAT is decreasing as we move through the diet phase and we probably hadn’t even realized it. Given that is it so important, I’ll have a separate post on NEAT soon.
The thermic effect of food (TEF) contributes ~10% to overall daily calorie burn. It represents the energy used (beyond BMR) to extract and process nutrients from the foods we eat – digestion, absorption, and excretion. At face value it doesn’t appear to be something that we have much influence over. However, we do have some degree of control over TEF through food selection. 10% is a general estimation and will be higher or lower depending on the relative amount of protein, carbohydrates, and fat you consume, as well a person’s fat free mass (leaner individuals generally have a higher TEF).
- Protein is the most energetically costly macronutrient for our bodies to process – 20 to 35%. For example, if I were to eat 350 kcal worth of protein, I need somewhere between require around 70-120 kcal to digest it.
- Carbohydrates require 5-15% of their energy to process. Fiber-rich carbohydrates will be on the higher energy burn end of the spectrum – think vegetables, fruits, rice, and whole grains – versus simple or highly processed sources.
- Fats require a minimal amount of energy to process – 0 to 5%. This doesn’t mean that we should avoid them to keep our TEF higher; fats serve and important role in the diet. Rather, we should focus more on unsaturated sources that can provide the most health benefits, e.g. olive oil, nuts, seeds, and omega-3 rich sources found in many types of fish.
Note: TEF is an area where the basic “calories in – calories out” equation is an oversimplification. Because we all use different amounts of energy to process the foods we eat, we cannot simply say that 100 calories worth of peanut butter is equal to 100 calories worth of chicken – once ingested they have different energy costs in our bodies so net calories will be different despite having an equivalent 100 calorie absolute energy value pre-ingestion.
Exercise Activity Thermogenesis (EAT) contributes ~5% to total daily energy burn. Although EAT usually contributes a lower percentage of your total calorie burn compared to NEAT, it is strongly influenced by exercise modality, duration, intensity, body size, and genetics. Try to get an hour of exercise 3 – 4 days a week. The health benefits extend far beyond basic weight management.
Bottom Line
As it relates to total daily calorie burn and fat loss, focus on what you can exert the most control over!
NEAT: Increase your general activity level during the day – if you have a sedentary job, dedicate specific times of day that you will stand up and walk around.
TEF: Your diet should contain adequate protein (0.8 -1 g/lb. of bodyweight) and contain carbohydrates sources that are high in fiber and minimally processed. Fats should remain in your diet from healthy sources.
EAT: Get some form of dedicated exercise 3-4 x week. Ideally, incorporate resistance training in your routine to support lean mass retention and fat loss/muscle gain, which will drive further increases across all key elements of total daily energy expenditure.
*You may also come across the acronym RMR, or Resting Metabolic Rate. BMR and RMR are slightly different, but for the purpose of this post they can be used interchangeably.
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