A common misconception around weight loss is that the less we eat, the smaller we’ll get. While it’s true that we lose weight when our energy intake is less than our energy expenditure, it’s possible to eat too little. When we eat too little, our body actually slows down our metabolism so that it can save the energy for our biological functions, like keeping our heart beating and our lungs breathing. This makes it harder for us to lose weight. Eating the right amount of calories can help you maximize your metabolism and get the most out of your workout.
Health Canada[1] has provided some helpful charts on estimated energy requirements based on age, sex, activity level, and the median heights and weights of Canadians in those categories. Take a peek – are you eating like someone your own size, or are you eating like a little kid?
Males (Calories per day)
| Age | Sedentary Level | Low Active Level | Active Level |
| 2-3 y | 1100 | 1350 | 1500 |
| 4-5 y | 1250 | 1450 | 1650 |
| 6-7 y | 1400 | 1600 | 1800 |
| 8-9 y | 1500 | 1750 | 2000 |
| 10-11 y | 1700 | 2000 | 2300 |
| 12-13 y | 1900 | 2250 | 2600 |
| 14-16 y | 2300 | 2700 | 3100 |
| 17-18 y | 2450 | 2900 | 3300 |
| 19-30 y | 2500 | 2700 | 3000 |
| 31-50 y | 2350 | 2600 | 2900 |
| 51-70 y | 2150 | 2350 | 2650 |
| 71 y + | 2000 | 2200 | 2500 |
Females (Calories per day)
| Age | Sedentary Level | Low Active Level | Active Level |
| 2-3 y | 1100 | 1250 | 1400 |
| 4-5 y | 1200 | 1350 | 1500 |
| 6-7 y | 1300 | 1500 | 1700 |
| 8-9 y | 1400 | 1600 | 1850 |
| 10-11 y | 1500 | 1800 | 2050 |
| 12-13 y | 1700 | 2000 | 2250 |
| 14-16 y | 1750 | 2100 | 2350 |
| 17-18 y | 1750 | 2100 | 2400 |
| 19-30 y | 1900 | 2100 | 2350 |
| 31-50 y | 1800 | 2000 | 2250 |
| 51-70 y | 1650 | 1850 | 2100 |
| 71 y + | 1550 | 1750 | 2000 |
Note: Sedentary level = Typical daily living activities (i.e. household tasks, walking to the bus)
Low active level = Typical daily living activities PLUS 30-60 min of moderate activity (i.e. walking at 5-7 km/h)
Active level = Typical daily living activities PLUS at least 60 min of moderate activity
Estimating your individual energy needs
There are lots of equations out there that can help you estimate your energy needs. Most of them calculate your resting metabolic rate (RMR), the amount of calories your body would use in 24 hours if you laid still; it’s the amount of energy your body needs to keep you alive. To get an idea of what your actual needs are, you will need to multiply your RMR by an activity factor based on your level of activity.
Cunningham Equation
This equation requires you to calculate your lean body mass (LBM). You can do this with your starting fat percentage for the Lean & Mean Challenge:
Weight (lb) _____ × Fat percentage (20% = 0.20) ___ = Fat mass _____ lb
Weight (lb) – Fat mass = LBM lb
Now you can plug it into the equation:
21.6 × (LBM ÷ 2.2) + 370 = Calories
Harris-Benedict Equation
If you don’t know your LBM or fat percentage, you can use the Harris-Benedict equation to estimate your BMR using just your weight, height, and age.
Males:
66.47 + (13.75 × Weight (kg) _____) + (5.0 × Height (cm) _____) – (6.76 × Age_____)
= Calories
Females:
655.10 + (9.56 × Weight (kg) _____) + (1.85 × Height (cm) _____) – (4.68 × Age_____)
= Calories
Activity Factors
Now, multiply your results from the equations above by the appropriate activity factor. This will give you the approximate amount of calories you will need to maintain your weight. For weight loss, remember that a pound of fat is about 3,500 calories. Creating a deficit of 500 calories everyday by decreasing intake and increasing activity will help you lose about a pound a week (500 Calories × 7 days = 3,500 Calories).
| Activity Factor | Category | Definition |
| 1.2 | Sedentary | Little or no exercise |
| 1.375 | Lightly Active | Light exercise or sports 1-3 days/week |
| 1.55 | Moderately Active | Moderate exercise or sports 3-5 days/week |
| 1.725 | Very Active | Hard exercise or sports 6-7 days/week |
| 1.9 | Extremely Active | Hard daily exercise or sports, or physical job |
[1] Estimated energy requirements – How much food you need every day – Canada’s Food Guide. http://www.hc-sc.gc.ca/fn-an/food-guide-aliment/basics-base/1_1_1-eng.php
