Here’s the four ways your body burns calories, and why trying to count your daily expenditure is an exercise is futility and frustration
If you’ve heard it once, you’ve heard it a thousand times: losing fat is all about calories in versus calories out. It’s pretty simple: eat fewer calories than you burn and you lose weight; eat more calories than you burn and you gain weight. But while calculating how many calories you need each day is relatively straightforward (here’s how to do it), estimating how many calories you’re actually burning is far more complicated. We’ll get to why, but first here’s the four main ways your body uses energy.
1 Resting metabolic rate (RMR)
RMR is the number of calories you burn each day at rest, just breathing, thinking and living. It represents around 60% of your daily energy expenditure and depends on your weight, body composition, sex, age, genetic predisposition, and the bacteria in your gut. In general a bigger body has a higher RMR, yet it can vary up to 15% from person to person. If you weigh 200lb (14st 4lb) with an RMR of 1,905 calories, someone else who weighs exactly the same as you could burn 286 more (or fewer) calories each day with no more (or less) effort!
2 Thermic effect of eating (TEE)
That’s right, it takes energy to process food. TEE is the number of calories you burn by eating, digesting and absorbing food and it represents around 5-10% of your daily energy expenditure. You’ll burn more calories digesting and absorbing protein (around 20-30% of its calories) than carbs (5-6%) or fats (3%), and you also burn more calories digesting natural whole foods than you do highly processed foods. If you’ve ever had the “meat sweats” or felt hot after a big protein-rich meal, that’s TEE in action!
3 Physical activity (PA)
PA is the calories you burn from purposeful exercise, such as walking, running, going to the gym, gardening, cycling or other physical activities. Obviously, how much energy you expend through PA is determined by how much you intentionally move around.
4 Non-exercise activity thermogenesis (NEAT)
NEAT is the calories you burn through fidgeting, staying upright and all other physical movements that don’t count as PA. NEAT output can vary tremendously between individuals. In studies where people are overfed, some individuals burn off 70% of those extra calories through NEAT alone, while others actually burn less! And in studies where people are underfed, some subjects’ NEAT output dropped dramatically (making it harder for them to lose weight), while others had minimal change in their NEAT output (making it easier for them to lose weight). Ultimately, NEAT output can vary by as many as 2,000 calories between individuals!
Ultimately, estimating your calorie expenditure is fraught with uncertainties and potential errors, so it’s almost impossible to accurately know how much energy you burn each day. Even fitness trackers, which are great at monitoring your heart rate, have been found to miscalculate wearers’ calorie expenditure by up to 30%, according to multiple studies.
As mentioned, the type of food you eat affect how many calories you burn – digesting protein burns more calories than carbs or fats, for instance – while unprocessed whole foods provide fewer dietary calories and require more energy to digest than highly processed foods.
There’s more. A single night of sleep deprivation can cause your metabolism to burn up to 20% fewer calories the following day, but your brain will seek out high-sugar and high-fat foods in response to tiredness so you eat far more calories than you need. Also, your previous weight history influences how many calories you burn at rest. So if you’ve ever been overweight or obese, your metabolic rate may be about 10% lower than someone of the same weight, age, sex and body composition who was never overweight or obese.
It is possible to get a good idea of how many calories you need to eat per day to maintain your current weight: from there you can then adjust your intake up or down depending on whether you want to gain weight or lose it. But it’s almost impossible to accurately estimate your daily calorie expenditure, so counting calories becomes an exercise in futility that takes time, effort and energy for a likely frustrating and unsuccessful outcome. That’s why we created the New Body Plan “Perfect Portion” approach to eating for fat loss, and you can discover how it works to help you lose weight and feel great here.