Since weight loss is subjective, factors such as age, weight, height, gender, and activity level need to be considered to reach a goal weight. A few simple calculations can create a rough idea of the caloric deficit needed for weight loss, as well as the amount of physical activity required.
The first calculation that needs to be done is the is the Harris Benedict Equation and the Basal Metabolic Rate formula. A BMR is the amount of calories needed to maintain body weight if a person slept all day, while the Harris Benedict Equation factors in energy usage based on activity level. In addition, this number is required in order to determine the caloric deficit needed for weight loss.
The BMR equation differs based on gender.
For females: 655 + (4.35 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years)
For males: 66 + (6.23 x weight in pounds) + (12.7 x height in inches) - (6.8 x age in years)
Next, activity level must be calculated. For sedentary activity, multiply BMR by 1.2. For activity done 1-3 times a week, multiply BMR by 1.375. For 3-5 times, multiply by 1.55. For 6-7 times, multiply by 1.725. For activity done 8+ times a week, multiply BMR by 1.9.
One pound is roughly 3500 calories. To lose one pound a week, a deficit of 500 calories needs to be created every day of the week. This can be done by burning 500 calories during cardio, or more realistically, subtracting 250 calories of food and burning 250 calories during cardio.
Calories burned are dependent on a person's stature as well as the speed, incline, and time of the workout. The heavier the person, the more calories burned. For example, a 140 pound adult running for 20 minutes at 7 miles per hour on a treadmill will burn 260 calories while a 170 pound adult would burn 317 calories.