Energy Needs

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.

Body Mass Index (BMI)

Body Mass Index (BMI)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. Use our calculator to figure your Body Mass Index (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


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.

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 calculate your estimated calorie needscaloric needs and it is probably best to use two or three methods to estimate calorie needs and then take the average.

Our three calculators can help calculate your estimated calorie needs. 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
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