This is the first question you need to answer if you want to change your body composition. It can be daunting thinking of all the formulas, macro splits, BMR, RMR, caloric maintenance, deficits, surpluses… you get my point.
But it’s really not. Calories are fuel. They fuel every single cell in your body and there are a lot of cells.
So you burn a lot of calories, just at rest. This is called the BMR - Basel Metabolic Rate - or RMR – Resting Metabolic Rate. It’s a mouthful but this is how many calories you would burn if you stayed in bed all day and didn’t even eat (because digesting food takes calories, called Thermic Effect of Food)!
Basel Metabolic Rate
There many online tools to calculate your BMR. From the really simple to the really complicated.
Here are the different factors that effect your BMR:
- Height one of the two biggest factors. The taller you are, the bigger you are which means bigger systems that are burning calories.
- Weight the other big factor. The more you weigh, the more lean body mass again more calorie burn. It’s also important to note even though muscle tissue burns more calories than fat at rest, fat is still metabolically active. So adipose tissue (fat cells) also help increase your BMR.
- Age doesn’t have a massive impact but the younger you are the faster your metabolism is.
- Sex favors males because they proportionally have higher lean bodymass by weight. The effect is minor though.
Lets look at how this would apply to some examples:
John is 22, 5’10 and 200lbs. He has a sedentary lifestyle.
His BMR would be around: 2000.
Jane is 22, 5’7 and 155lbs. She also has a sedentary lifestyle.
Her BMR would be around: 1540.
Daily Caloric Maintenance Level or Expenditure
Again it’s important to note that BMR isn’t the total amount of calories you burn everyday. It’s the amount of calories you burn if were in bed all day and didn’t have to digest any food . So your actual amount you burn is Daily Calorie Expenditure or Caloric Maintenance or Total Energy Expenditure (TEE).
Caloric maintenance is how many calories you effectively burn everyday. This is the number you need to worry about, not BMR. This number is dependent mostly on your daily activities. It’s not all exercise, in fact exercise is a small part, the rest is you going through life. Standing, walking, running, going up stairs, cooking, cleaning, moving, etc.
To calculate your maintenance you can use the Harris Benedict equation:
- Sedentary (Sitting all day, no exercise): 1.2
- Light activity (Moving a bit during the day, daily walk or light exercise): 1.375
- Moderate Activity (More demanding job/regular exercise): 1.55
- High Activity (Very demanding job/regular exercise): 1.725
- Very high activity (Very demanding job and hard exercise): 1.9
So back to our example John and Jane are both sedentary so we’ll use between 1.2 and 1.375 multiplier.
John: 2000 x 1.25 = 2500
Jane: 1540 x 1.25 = 1925
So this is the number you want to work with. From here you want to create a caloric deficit; that is: eat LESS than you burn.
Lets say you are aiming to burn 1lb of fat per week:
- 1lb of fat is equivalent to 3500 calories.
- That means you need a WEEKLY deficit of 3500 calories.
- Your daily deficit would be 500 which you subtract from your maintenance level.
And voila the caloirie target for our theoretical clients are:
John: 2500 (maintenance level) – 500 (daily calorie deficit) = 2000 (daily calorie target)
Jane: 1925 – 500 = 1425
Now that you know how many calories to eat you can split it up into 3 or 4 balanced meals. The goal is to stay within your calorie goal. So if your goal is to eat 1600 calories a day that would mean 400 calories per meal for 4 meals.
Conclusion
So set a plan, break down the numbers and start working on your goals. We recommend aiming to lose 1-1.8lbs per week, not more. Having a huge deficit doesn’t really work.
Fat loss is a long term process and you are more likely to win the lottery than to succeed with a crash diet.