A calorie is a measurement of energy. Specifically, it’s the amount of energy required to increase the temperature of 1 gram of water by 1°C. Now think about your body. At the end of the day you get tired and feel the need to sleep. You need energy. Every action you do requires energy, and your body utilizes energy from food or previously stored food (fat, glycogen, etc.) to do so.
Depending on how much you weigh, here are some activities you can use to bring calories into perspective. Doing 50 squats burns around 40 calories. Running a mile burns around 100 calories. Brushing your teeth for 2 minutes burns about 5 calories. Everything you do has a cost associated to it, and that cost is energy in the form of calories.
When you eat, your body utilizes the carbohydrates, protein, and fat to perform daily functions or store energy for later use.
Now this is where things get interesting. Your body inherently burns a certain number of calories simply by existing. This is known as your Basal Metabolic Rate (BMR). Even when you sleep, or digest food, your metabolism increases. This is considered with what is known as Resting Energy Expenditure (REE) or Resting Metabolic Rate (RMR). Lastly, add in all the physical activity such as walking, weight lifting, writing, and anything else you do throughout the day consciously. This is referred to as Total Daily Energy Expenditure (TDEE).
You don’t really need to understand all the specifics or remember all those terms. What’s important to understand is that your TDEE when compared to how much you eat (Energy Consumption) will determine how your weight responds.
If you eat 2,300 calories and your TDEE is 2,300 calories, then your weight will typically stay the same. Now what if you want to gain or lose weight? When you eat less than you burn, this is known as a calorie deficit. When you eat more than you burn it is known as a calorie surplus. When you’re in a calorie deficit your body will lose weight, whereas with a surplus you will gain weight.
To lose a pound of fat you need to be in a calorie deficit of 3,500 calories. To build a pound of muscle you’d need to be in a surplus of 2,500 calories.
Now listen carefully. Don’t just stop eating, and don’t just put yourself in a massive deficit! This can be highly dangerous and harm you irreparably. Typically, you’ll want to aim for around 1-2 lbs. of weight loss each week according to the CDC. This would be 3,500-7,000 calories each week. In other words, this is a deficit of 500-1,000 calories each day. According to the USDA men need from 2,000-2,600 calories daily for healthy calorie balance and women need 1,800-2,000. You may be able to go lower than these ranges, but I typically don’t recommend men going lower than 1,600-1,800 and women 1,200-1,400 for more than a few days at a time. (Obviously you’ll want to check with a physician prior to changing anything about your diet or exercise).
Alright, now that we’re through the most of calorie essentials, you’ll want to adjust your calories by about 500 up or down depending on your goal and adjust exercise and activity to account for the remainder of the deficit or surplus.