When managing nutrition for weight loss or weight gain goals it can be helpful to know how many calories your body uses day to day. For example, who want to lose weight will need to create a calorie deficit (consuming fewer calories than their body uses) over an extended period of time (1.). Anyone wanting to to build muscle will benefit from a moderate calorie surplus in combination with appropriate resistance training. Managing either of those is easier when you have an understanding of both output and input.
There are four main elements to TDEE: metabolic rate, thermic effect of food, non-exercise activity and exercise.
Basal Metabolic Rate
This is the baseline number of calories or that the body requires to stay alive, the energy to support breathing, organs functioning at a resting state. The BMR number makes up around 70% of the bodies daily energy needs. Even if you were asleep for whole day your body would still need a fair amount of energy to keep going. A rough calculation for this number is 20 x body weight in kilos. For example, 70 kg x 20 = 1,400 calories. The heavier a person is the greater their minimum energy requirements will be (which is affected by overall weight including height and muscle mass).
Even when seeking a calorie deficit for weight loss, in order to help maintain general health and fitness, I would suggest it's sensible to have this number (your personal BMR) as a minimum. Very low calorie diets are very difficult to maintain for any length of time and when people come off them any weight loss that occurred is likely to be short lived. That's if the diet is adhered to. A more likely scenario is that low energy, brain fog, and grumpiness that can occur when restricting food triggers a binge of lots of tasty calorie dense foods which disrupts the weight loss attempt.
Thermic Effect of Food
The process of consuming and digesting food increases the bodies energy demands by about 5%. Considering that this something we do every day it doesn't really count as 'extra' calories burned and is a very low number anyway (around 140 calories working from the same example as above).
Those myths you may have heard about chillies or celery juice helping to boost this effect are just myths. Even if there is something to it, it would a very small boost to a very small number so not worth getting excited about.
Non-Exercise Activity Thermogenesis
Also known as 'NEAT'. Now this one is worth getting excited about. In fact at least one Insta-famous PT has made it part of his brand. Non-exercise activity is basically any activity you do that isn't exercise and 'thermogenesis' means heat production. It covers a LOT, like stretching when you wake up in the morning, brushing your teeth, making a cup of tea, going around the supermarket, walking from the car to the gym, even just fidgeting around while watching TV. Most of these will only burn a few calories each but over the course of an entire day, depending on how much you do, it can add up. This is estimated to account for around 15-20% of your daily energy expenditure, again using the example above that would be around 400 calories although it does vary. An office worker sat behind a desk most of the day would have lower energy requirements than someone who stacks shelves. Body composition can also make a difference. Those with a higher muscle mass use more energy; it is estimated that one pound of muscle uses six calories per hour and one pound of fat uses two calories per hour.
Keeping the body active and moving throughout the day has health benefits beyond simply burning energy. It helps keep the heart healthy and the joints mobile. So, for all of these reasons a good coach or PT will recommend that you aim to keep your 'NEAT' activity levels up for at least 5-6 days per week (resting is important too). Aiming for 10,000 steps a day is one of the ways to do this.
Exercise Activity Thermogenesis
That brings us to intentional exercise. Any maths wiz may have worked out already that this number makes up the remaining 5-10% of our bodies energy demands (2). Although it is a small number in the overall picture of the calorie demands on our bodies it is important to make this a priority for a number of different reasons. The benefits to physical health, strength, mental well being, a way to make social connections, and on make it absolutely worth the effort.
However, what this does mean is that, for a weight loss goal, adding one or two workouts a week is not going to shift the needle very far in the direction of a calorie deficit (this is what is being referred to when people say things like 'abs are found in the kitchen'). One way to help make the most of the exercise you do is to include resistance / strength training in your routine as, mentioned above, maintaining or increasing muscle helps increase overall energy expenditure.
Calculating Your TDEE
The easiest way to do this is using a free calculator like the one here. This asks for basic information (age, weight, height, activity level) and provides estimates of how many calories would be needed for weight maintenance, weight loss or gain as well suggestions for macronutrient splits (carbohydrates, protein, and fat) for anyone who is tracking those.
For help making sense of these numbers and how to apply that information in relation to your goals please contact me via the form below.
1. It is absolutely possible to achieve weight loss without knowing about or tracking calories but the process underlying that will still be the body using more energy than is taken in.
2. There will be some exceptions to this, someone training for an ultra-endurance type event like a long distance triathlon will have a higher average exercise percentage but typically those training periods build over a period of 4-6 months then revert back to more normal levels.