Whether you’re trying to lose or gain weight, calories are key to the whole equation. Calories are, in essence, a measure of the energy found in food. When you eat fewer calories than you need, your body starts to burn up some of the fat it has stashed away for fuel – and weight loss is accomplished. Taking in more calories than you need, however, means that it will get stored for emergencies. Depending on the type of food you’re eating and your workout routine, this could mean more fat or more muscle – or, more like, a little of both.
So, regardless of what your goals are, understanding how many calories you actually need – and how many calories you’re eating – is vitally important.
Factors and Formulas Involved
One of the major problems that comes up in trying to sort out caloric needs is just how many factors influence how your body uses that energy. Your height, weight, gender, age, activity level, workout style, fitness level, diet, sleep schedule, hormonal balance and general health all play a role in determining how many calories your body burns throughout the day – and, by extension, how many calories you need to eat.
To get a general estimate, though, you need to start with your Resting Metabolic Rate (RMR) – the amount of calories your body uses to just be alive. There are several different formulas used to find RMR and calculators litter the internet. So that you have a rough idea of what’s going on, here is the basic Mifflin-St Jeor Equation – generally considered fairly accurate.
For men: BMR = 9.99 x weight (kg) + 6.25 x height (cm) – 4.92 x age (years) + 5
For women: BMR = 9.99 x weight (kg) + 6.25 x height (cm) – 4.92 x age (years) – 161
As mention, though, your fitness level can greatly impact the amount of calories that your body burns even at rest. Primarily, this is because muscle burns large amounts of calories. A very lean person, then, will generally need more calories to support biological activities than someone with a higher body fat percentage. For those with a more athletic build, the Cunningham formula will be more accurate. (Note: This formula requires you to know your lean body mass (LBM). To find this, multiply your total body weight by your body fat percentage.)
500 + (22 x LBM)
Now, here’s the thing, you aren’t just sitting around doing nothing all day. Or, at least, we hope not. You’re running around, being awesome. And all that greatness burns calories, so you need to do just a bit more math to compensate. Namely, you need to figure your total energy expenditure (TEE) – how many calories you burn on a normal day.
To do that, you’ll need to consult the following chart and (honestly) identify how active you are.
Your TEE, then, will look like this:
TEE = RMR x activity factor
Consider Your Goals
Your TEE, though, isn’t necessarily how many calories you need to eat every day. Instead, that number represents how many calories your body uses to maintain it’s current weight. You may not be interested in maintenance. If you’re looking to gain weight, you’ll need to eat above your TEE. Exactly how much you add is up to you and how much poundage you’re looking to add.
Logically, then, the opposite is true for weight loss. On average, more experts recommend cutting no more than 500 calories off your daily caloric intake. Depending on your situation, this will typically result in about one pound gone each week.
So, there you have it: All the math involved in figuring out how many calories you should be eating. Or, you could skip it and just use a calculator with all that nonsense already built in.