So when it comes to losing or gaining weight it comes down to energy balance. Let's pretend that our body is a bank account, money goes into the bank and money goes out of the bank.
The incoming money is the food (energy) we consume and the outgoing money is the energy we expend throughout the day through several sources (More on those down below)
If you spend more money than you put into the bank you will be in debt (energy deficit), and if you save more money than you spend you will have savings (energy surplus).
Let's talk about the different ways you 'spend' energy.
BMR : Basal Metabolic Rate, this is the energy the body requires to simply function, blinking, breathing, keeping your heart pumping etc.
TEF: Thermic Effect of Food, it requires energy to breakdown and process food that we consume.
NEAT: Non Exercise Activity Thermogenesis, to keep this simple its activity that you perform on a day to day basis, walking, carrying the shopping, taking the dog out for a walk. Activity that you wouldn't consider as exercise
Exercise: Pretty straight forward this one, going to the gym, swimming, dancing, trampolining etc. Anything you do as recreational activity
These when added added together will give you your TDEE
TDEE : Total Daily Energy Expenditure, this is your 'spending' when it comes to the bank analogy.
You will notice that a large chunk of our energy is 'spent' through our BMR and a relatively small amount generally less than 25% is through physical activity.
Let's talk more about your BMR.
Here are ten factors that contribute BMR :
1. Age. As you age, your metabolic rate generally slows. This is because of a loss of muscle tissue and changes to hormonal and neurological processes. During development children go through periods of growth with extreme rates of metabolism.
2. Body size. Those with bigger bodies have a larger BMR because they have larger organs and fluid volume to maintain. Think a larger building requires more energy than a smaller building.
3. Gender. Men generally have faster metabolisms than women.
4. Genetics. Some families have faster BMR than others with some genetic disorders also affecting metabolism.
5. Muscle mass. The amount of muscle tissue on your body. Muscle requires more energy to function than fat. So the more muscle tissue you carry, the more energy your body needs just to exist. (Resistance or strength training is most effective for building and maintaining mass.)
6. Physical activity. Exercise increases muscle mass and powers up your metabolic engines burning kilojoules at a faster rate, even when at rest.
7. Hormonal factors. Hormonal imbalances such as hypo & hyperthyroidism can affect your metabolism.
8. Environmental factors. Environmental changes such as increased heat or cold forces the body to work harder to maintain its normal temperature and increases BMR.
9. Drugs. Caffeine and nicotine can increase your BMR whilst medications such as antidepressants and steroids increase weight gain regardless of what you eat.
10. Diet. Food changes your metabolism. What and how you eat has a big influence on your BMR.