Do I really need calories?
We may not like them but we need calories to live. This minimum number is called the basal metabolic rate (BMR). Your BMR is the number of calories your whole body needs to function while you perform no activity whatsoever. So even if you lie in bed all day watching Netflix your body requires calories. In fact, on a daily basis about 70% of the calories you consume are used to keep your organs and cells operating.
Since your basal metabolic rate is based largely on involuntary functions like breathing and pumping blood, changes in your day-to-day activity don't do much to raise or lower this number. This is calculated by your Total Daily Energy Expenditure (more on this later). However, increasing muscle mass does increase BMR, because muscle is metabolically "hungry" and it takes more energy to maintain more muscle. This means that when you have a lot of muscle mass, you'll burn more calories at rest.
Why does it matter?
Once you know your BMR, you can use it to calculate the calories you actually burn in a day. From there, you can determine how many calories you need to eat to gain muscle, lose fat, or maintain your weight. Let's work it out:
Step 1
Measure your height in inches. Convert the result to centimeters by multiplying by 2.54. For example, if are you are 70 inches tall, you multiply 70 by 2.54 to get 178 cm. Or if you know the centimeters great!
Step 2
Weigh yourself on a scales in KG's.
Step 3 (For Men)
Calculate the BMR for males in units of calories per day. The following equation provides this calculation:
BMR = (height in centimeters x 6.25) + (weight in kilograms x 9.99) - (age x 4.92) + 5.
For example, if your height is 178 cm, your weight is 78.6 kg and your age is 37, you would use:
(178 x 6.25) + (78.6 x 9.99) - (37 x 4.92) + 5 = 1,721 calories per day.
Step 3 (For Women)
Calculate the BMR for females in units of calories per day. The following equation provides this calculation:
BMR = (height in centimeters x 6.25) + (weight in kilograms x 9.99) - (age x 4.92) - 161.
For example, if your height is 178 cm, your weight is 78.6 kg and your age is 33, you would use:
(178 x 6.25) + (78.6 x 9.99) - (33 x 4.92) – 161 = 1,574 calories per day.
If you're trying to lose weight, keep track of your BMR as it will change as you lose weight. Your BMR will drop along with your weight.
Total Daily Energy Expenditure
The overall number of calories your body uses on a daily basis is referred to as your "total daily energy expenditure" (TDEE). It's based on your BMR as well as your activity level throughout the day. This varies significantly based on your activity level, age, and sex. Generally, men have a higher TDEE than women because they have more muscle mass, and both TDEE and BMR tend to fall regardless of gender as you age. The older we get the slower calories are burnt up for energy so we need less. It's also why staying lean in your 20's was a piece of cake.
You can use the below TDEE calculator to find this number. Keep in mind, though, that it's impossible to know your exact TDEE, as your activity levels will change day to day, and the only way to get 100 percent accurate BMR numbers is through professional testing. But don't worry, this will be enough for you to work off.
What's the Difference between BMR and RMR?
Just to confuse you more the term BMR is sometimes used with RMR, which stands for "resting metabolic rate." The difference is that while BMR only measures basic processes of breathing, blood circulation, and temperature regulation in a completely resting state, RMR also includes energy expended by digestion and non-exercise daily movements, like getting dressed and lifting your fork to your mouth.
Since the calories you burn digesting food and doing things like brushing your teeth tend to stay around the same range on most days, either number can be used when you're just trying to get a rough estimate of how many calories you burn not including your workouts. Unless you're being tested in a lab environment, both of these numbers will only be estimates, but they can still give you targets to shoot for when you structure your meal plan and workouts.
How does this all help?
Once you use your BMR and determine your TDEE, you can make sure that the nutrition plan you follow is appropriate for your level of energy expenditure and that it isn't giving you too many or too few calories. Being armed with this knowledge, rather than guesstimating or blindly following a plan without scaling it to your individual needs, can make or break your muscle gains or fat loss. Good luck!