TDEE is composed of the following -
BMR (Basal Metabolic Rate)
This denotes the calories you burn at rest every day. Your BMR supports the daily functions your body must do simply to exist - breathing, blood circulation, body temperature, repairing cells, and brain activity for example. If you were to lay down all day, not move, eat or drink - you are still burning energy just to keep you alive. The most common way to increase your metabolism is by increasing your muscle mass. The more muscle you have, the higher your BMR is going to be. As you build muscle, you’ll notice that your appetite increases, because your body now requires more calories to maintain that muscle mass.
TEF (Thermic Effect of Food)
These are the calories we burn through digesting food and absorbing the nutrients from food. Some foods require more energy to digest which is why you’ll often see articles about ‘foods that help boost your metabolism’ - they don’t boost it, they just take a little more energy to break down. Protein is one of these food groups - your body uses more energy to break protein down. It’s one of the reasons why everyone recommends eating protein when you are attempting to lose weight.
NEAT (Non-Exercise Activity Thermogenesis)
It means the calories we burn through movement outside of planned exercise. Any movement that is unplanned is NEAT - getting out of bed, walking to the kitchen to have breakfast, running for the bus, walking to the lift at work, shifting around in your seat, walking to grab lunch, brushing your teeth and everything in between. If you are a very active person outside of the gym, your NEAT is going to be very high and you’re going to be burning more calories throughout the day.
EAT (Exercise Activity Thermogenesis)
If you choose to head out for a walk, run, cycle, swim, dance or do a weights workout, this counts as EAT. It’s simply any exercise that you have planned.