Our bodies require energy (in the form of calories found in the food we eat) to run effectively. If we sit for most of the day and aren’t physically active then we require less energy. If we are very active and engage in exercise and vigorous activity then we require more energy. The body is using up more energy stores to perform more work and burns through calories much quicker. The “gas tank” needs to be full in order to work effectively during both exercise and recovery.
To effectively determine the amount of calories you need to consume each day there are several factors to consider:
- Body composition (lean body mass, body fat)
- Physical activity and exercise
The Harris-Benedict equation is a formula that can be used to calculate the number of calories required to essentially keep our bodies running when it is at rest (basal metabolic rate or BMR). Your BMR is then used, in conjunction with your activity level, to calculate the amount of calories needed to maintain your current body weight. By understanding the number of calories we need at our current body weight we can then effectively determine a strategy to reach a goal weight in an effective manner (i.e. weight loss or weight gain).
Harris-Benedict Equation for Men
Due to gender differences the calculations for men and women are not the same. Males tend to have more lean body mass and a lower body fat percentage than women.
Step One: Determine your basal metabolic rate (BMR) using the equation below.
BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years)
Step Two: Apply the Activity Multiplier that best describes your level of activity to calculate your total daily energy expenditure (TDEE) using one of the equations below.
- Sedentary (very little or no exercise): TDEE = BMR x 1.2
- Lightly Active (light exercise or sports 1-3 days/week): TDEE = BMR x 1.375
- Moderately Active (moderate exercise or sports 3-5 days/week): TDEE = BMR x 1.55
- Very Active (hard exercise or sports 6-7 days/week): TDEE = BMR x 1.725
- Extremely Active (very hard exercise or sports 6-7 days/week): TDEE = BMR x 1.9
Once you’ve determined the calories your body requires to maintain your current body weight you can then determine the calories you need to achieve your goal weight. Let’s look an example of a man who is looking to effectively gain muscle mass.
- Weight: 160 pounds
- Height: 72 inches (6 feet)
- Age: 36 years
- Activity Multiplier: Moderately Active
- BMR = 66 + (6.23 x 160) + (12.7 x 72) – (6.8 x 36)
- BMR = 66 + 996.8 + 914.4 – 244.8
- BMR = 1732.4 kCal
- TDEE = BMR x 1.55
- TDEE = 1732.4 x 1.55
- TDEE = 2685.2 kCal
This person requires 2685 calories per day to maintain his weight at 160 pounds. In order to effectively increase his weight he must increase his daily caloric intake by an amount that doesn’t upset the body’s comfort level. If you increase the caloric intake by too much or the body’s metabolism may slow down significantly, causing weight gain rather than gradual increases in muscle mass. An increase of 15 to 20 percent is an appropriate increase for positive results.
- Daily Calories for Weight Gain = TDEE + (TDEE x 0.15)
- Daily Calories for Weight Gain = 2685.2 + (2685.2 x 0.15
- Daily Calories for Weight Gain = 2685.2 + 402.8
- Daily Calories for Weight Gain = 3088 kCal
With an increase of 402.8 calories per day, while maintaining his level of physical activity at a moderate level, this man can expect to gain muscle mass over time. Unlike weight loss, which is much easier to predict, gains in lean muscle mass requires the development of new tissues. There are several variables that dictate to speed at which this occurs. This includes duration, frequency and intensity of the workouts in addition to rest, recovery and proper nutrition for muscle development. Use these guidelines but monitor your progress and adjust your caloric intake and exercise program accordingly.