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Calories reflect energy or fuel available to support any physical performance. To determine how many calories are needed, generally begins with an assessment of body weight and/or body composition.
One common method of assessing body weight is body mass index or BMI. Although BMI is a rough index, it is considered better than height-weight tables. BMI has been correlated with risk for various disease such as cardiovascular complications (hypertension and stroke), certain cancers, type 2 diabetes, gall stones, osteoarthritis, and renal disease.
BMI - Body Mass Index: BMI Calculator
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CAUTION: BMI in children, elderly, and athletes is difficult to interpret because the muscle and bone weights are changing in relationship to height. For this reason, athletes and active individuals can mistakenly be classified as overweight by BMI.
To assess your BMI use the following:
| BMI | Weight Status |
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Normal |
| 25.0 – 29.9 | Overweight |
| 30.0 and Above | Obese |
Body Composition
Because of the extra muscle mass an athlete or active individual develops as a result of training and exercise, they may be misclassified as overweight by BMI. Extra muscle mass does not have the negative health implications that excess fat does.
For this reason, athletes and active individuals should have their body composition assessed rather than using BMI whenever possible. Body composition quantifies structural components of the body including muscle, bone, and fat. There are a number of ways to estimate body composition including skinfold measurements, bioelectric impedance, dual energy x-ray absorptiometry, and air displacement (BOD POD). For a more complete description of the methods to assess body composition visit the Georgia State University Exercise and Physical Fitness Page.
Contact your local health care facility (medical clinic, hospital, public health agency), college/university or a Registered Dietitian to identify methods of body composition assessment available in your community.
Estimated Calorie Needs Calculators
Calorie needs for everyone, including athletes, are based on age, sex, body weight and activity. There are a number of formulas to estimate caloric needs and it is probably best to use two or three of the following methods to estimate calorie needs and then take the average.
REMEMBER: The calorie estimate provided is based on the information provided by the user, whether it is correct or not (i.e. weight, activity level). In addition, this is only an estimate of caloric needs; for individualized recommendations, locate a Registered Dietitian in your community.
Source: Mifflin equation for Resting Energy Expenditure (formula published by Mifflin and colleagues, Am J Clin Nutr 1990)
2. Calories per pound rule of thumb
Source: Mosby's Nutritional Care Pocket Guide 2001
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Remember estimated calorie needs from any of these formulas are based on current weight and are the number of calories required to maintain the current weight with the current activity level. Average the estimated calorie needs of formulas above to maintain current weight.
If you would like to lose weight:
- Subtract 500 calories from the estimate for a 1 pound weight loss per week OR
- Increase physical activity approximately 60 minutes per day for a 1 pound weight loss per week OR
- Do both and lose 2 pounds per week
- Another way to estimate calorie needs for weight loss is to use the desired weight rather than current weight in the formulas provided above
Last update: 1.25.06
Contact: Kristin Taylor