Calories: We Do the Math With You


IIFYM (If it fits your macros) is a term tossed around the internet constantly. There are a lot of differing opinions on whether you should eat according to your macros or just "eat clean". There is importance to both,

but at the end of the day, calories are still calories, even if they came from a hamburger or from a salad. So determining the total amount of calories your body requires will go a long way in helping you achieve your goals, may it be weight gain, maintenance or loss.


What separates it from the rest?

The term "clean eating" gives the impression that it doesn't matter how much you eat, as long as it's "clean". What if you ate 4,000 calories of clean food, but your daily calories only allowed you 2,700. Would you still get fat? Of course you would if you're not using the extra 1,300 calories you're taking in.

Rather than emphasizing the need to pick foods that are "clean" (freshly grown, which you should eat anyways), it emphasizes having the ability to pick the kinds of foods you like to eat and being able to have variety in your meals. The chicken and broccoli only diet to lose weight is only good for so long.


So why are all three macronutrients important?

For starters, carbs are essential for energy in our bodies. They're the body’s preferred fuel source, as they're used for brain function, as well as the main source of energy for exercise.

Fats work as insulation to protect our internal organs, to carry fat-soluble vitamins (A, D, E and K); and as an important structural component of all of our cells’ membranes, hormones and in our nervous system.

Proteins are essential for building muscles, but also other body tissue structure. They also play a key role in forming enzymes for essential bodily functions like food digestion. Without all of these, the body is not able to perform all of its necessary functions properly.

But how do I figure out what I need? (There is some math involved, grab your calculator)

First we need to determine the amount of calories required by your body to survive, this is called your Basal Metabolic Rate (BMR), or essentially the amount of calories your body needs just to complete it’s essential functions, without adding any physical activity (including activities of daily living - sitting, standing, walking, etc.).


Women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)

Men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in year)

For example, if we have a 150lb female, who is 5’8” (68 inches) and 25 years old, we would find her BMR to be:

BMR = 655 + (4.35 x 150) + (4.7 x 68) - (4.7 x 25) = 1510 kcal/day


Then we use the Harris Benedict equation to add on an approximate amount of calories to cover the calories used in activities of daily life. To determine the approximate total amount of calories your body uses/needs in a day, we multiply our previously determined BMR by one of the following factors:


  • If you are sedentary (little or no exercise) : Calorie-Calculation = BMR x 1.2

  • If you are lightly active (light exercise/sports 1-3 days/week) : Calorie-Calculation = BMR x 1.375

  • If you are moderately active (moderate exercise/sports 3-5 days/week) : Calorie-Calculation = BMR x 1.55

  • If you are very active (hard exercise/sports 6-7 days a week) : Calorie-Calculation = BMR x 1.725

  • If you are extra active (very hard exercise/sports & physical job or 2x training) : Calorie-Calculation = BMR x 1.9 (From


For example, our female is moderately active, she works out at the gym 3 days a week and runs once a week at home (4 workouts per week):

1510kcal/day x 1.55 (moderately active) = 2340 kcal/day


This gives us an approximate amount of calories that would comfortably sustain her current body weight while meeting the energy demands of her every day life and exercise regime. However this number may change depending on goals.

If she was looking to lose weight, we could subtract an amount of calories from this total to assist the body in using some of it’s own body fat stores to create the energy deficit. Typically we would suggest a decrease of up to 500 kcal/day, so she would take in about 1840 kcal/day.

If she was looking to gain weight, we would add extra calories on, depending on their goal. Typically we would add between 300-500 kcal/day to begin and re-assess in a few weeks time to determine if further calorie addition is needed. The decision of which macronutrient goes depends on the person. Some people prefer more fats in their diet, and some prefer more cards or protein.

Now that we have determined our approximate caloric needs for our lifestyle, we can break down that total amount into needs for carbohydrates, fats and protein.

The typical Canadian consumes nearly 70% of their calories from carbs. This isn’t ideal for the body for a number of reasons. Not only in terms of the risk for diabetes and other blood sugar control issues, but the metabolism of carbohydrates is not a very energy expensive process. The digestion and metabolism of proteins requires more energy from the body to complete, so having a higher amount of protein in the diet aids boosting the metabolism.

To show how we break down these amounts to determine the amount of grams of each we need in a run of a day, using our same female example with a need for 2340 kcals per day, on a “lower carb” day:


  • Carbohydrates at 50% x 2340 = 1170 kcal / 4kcal/g = 292.5 grams

  • Protein at 30% x 2340 = 702 kcal / 4kcals/g = 175.5 grams

  • Fat at 20% x 2340 = 468 kcal / 9kcal/g = 52 grams


Filling your macronutrient needs requires a good amount of logging of the foods you eat. You should expect it to take some amount of time to learn the breakdown of foods you commonly eat. I would highly suggest using an online tracking system, My Fitness Pal (online and app available) is a very popular system.

You can find nearly every food item available in stores and popular restaurants on it. With time you will get a hang of the breakdown of many foods and become comfortable estimating your intake. This approach is a tried and true method, however it is not perfectly exact to every single body.

Using a heart rate monitor or other devices that monitor body activity 24/7 (for example, FitBit) may help you get a closer number to your exact needs, if you so choose. For other types of dieting - i.e. competition dieting, the breakdown of the nutrients may fluctuate further to decrease the amount of carbohydrates in the diet.

One important piece of advice if further increasing your protein intake is to ensure proper hydration, in the breakdown of protein in the body, we need to excrete nitrogenous waste which requires sufficient water. A female should consume approximately 2.7 L of water per day and a male should aim for 3.7 L per day, both plus extra for exercise.

In addition to this, it is important to remember to get adequate fibre in the diet to aid digestion. We should aim for a minimum of 25 g/day to upwards (or beyond) of 50 g/day. If you have a low-fibre diet, slowly increase the amount of fibre to avoid cramping, gas and loose bowels that can come with changing - Fitting your macros allows you to eat the kinds of foods you want, even allowing room for some treats.

However, the majority of the food should be whole foods that are rich in vitamins, minerals and fibre. Over-consuming packaged and manufactured foods leads the body to  nutrient-deficiencies, complete with digestive problems and poor healing after exercise or illness among other problems.

Determining the caloric needs of your body is essential for achieving or maintaining  a healthy weight, but as well for providing enough energy to gain strength, speed and stamina. The body's energy needs are a science, and taking a moment to calculate your needs will go a long way in achieving your goals, whatever they may be.



BMR Calculator

Harris Benedict Equation

Laura Johnston is a certified Holistic Nutritionist based out of Edmonton, Alberta. She consults with major brands like Sobeys and World Health Edmonton and offers her expertise to clients looking to improve their lifestyles through habit building and healthy eating.