Maintaining a healthy body weight and body fat percentage is one of the best practices to ensure optimal health, fitness, and physical performance.
The best way to maintain a healthy body weight and body fat percentage is to follow sound dietary practices and to engage in physical activity. These practices will also promote muscle endurance and strength, improve cardiorespiratory conditioning, and provide a solid foundation for optimal physical performance. In addition, people who maintain a healthy body weight have a lower risk of developing psychological problems related to low self-esteem and low self-image. All of these issues are relevant in maintaining military readiness, force health protection, and in promoting optimal health of military personnel. This chapter introduces you to the basic concepts of energy balance and body composition.
The difference between energy intake, how many kilocalories (kcal) we eat, and energy expenditure, how many kcal we burn, is termed energy balance. Eating the same number of kcal as you burn leads to a net energy balance of zero, and your current weight is maintained. Eating more or less kcal than you burn leads to positive (weight gain) or negative (weight loss) energy balances, respectively.
Sensitivity of Energy Balance
This energy balance equation can be unbalanced by changing energy intake, energy expenditure, or both, as shown in the following examples. (1 pound (lbs.) of fat equals 3,500 kcal.)
If you maintain your kcal intake and run an extra mile per day, 5 days per week, you would expend an extra 100 kcal/mile x 5 miles/week x 52 weeks = 26,000 kcals per year. This would result in a net weight loss of 7.4 lbs. per year (26,000 ÷ 3,500).
The energy balance equation is very sensitive!
Components of Energy
Energy requirements are based on daily energy expenditures. The three major contributors to energy expenditure are:
- Basal metabolic rate (BMR).
- Energy for digesting foods.
- Physical activity.
Basal Metabolic Rate
Basal metabolic rate (BMR) is the amount of energy required to maintain life such as breathing, beating of the heart, and maintaining body temperature. This accounts for the majority (~70%) of the total daily kcals expended. BMR can be estimated by using the equations down. Find the equation that is appropriate for you and calculate your BMR.
Equations to Calculate BMR (kcal/day)
6.95 x body weight (lbs.) + 679
5.27 x body weight (lbs.) + 879
6.68 x body weight (lbs.) + 496
3.95 x body weight (lbs.) + 829
The body must work to digest food. However, the energy needed for digestion is only a small amount and has been accounted for in the BMR equations.
Estimate Your Activity Factor
|Level of Activity||Activity Factor|
|Very Light||Seated and standing activities, driving, playing
cards, computer work.
|Light||Walking, sailing, bowling, light stretching, golf,
woodworking, playing pool.
|Moderate||Jogging, aerobic dance, light swimming, biking,
calisthenics, carrying a load.
|Strenuous||Stairmaster, ski machine, racquet sports,
running, soccer, basketball, obstacle course,
digging, carrying a load uphill, rowing.
|Exceptional||Running or swimming races, cycling uphill, hard
rowing, carrying heavy loads.
Calculate Your Estimated Energy Requirement (EER)
Energy Needs = ----------- X -----------------------
*BMR * Activity Factor
Your Estimated Energy Requirement (EER) = _______kcal/day.
This EER is the amount of kcals you need to eat daily to have an energy balance of “zero” and maintain your current body weight. If you restrict the number of kcals you eat per day, your BMR will decrease because your body will sense that it is being “starved”. If your goal is to lose weight, you should lower your caloric intake only slightly and engage in a well rounded exercise program. Your goal should be to lose 1/2 - 1 lbs. per week. If you are losing more weight than this, you are losing water and lean tissue (muscle). If you want to gain weight, your goal should be to gain 1/2 - 1 lbs. per week. The objective is to gain lean mass, not fat. Exercise routinely, including strength training, and increase your caloric intake by using the Food Guide Pyramid guidelines. Also, eat healthy snacks between meals.
The Body Mass Index (BMI) is commonly calculated for assessing body composition. It is a ratio of body weight in lbs. to body height in inches.
Calculate Your BMI
Your BMI = -------------------------- x 705 ÷ (------------------------- )2 = .
Body Weight (lbs) Height (inches)
Classifications for BMI Ratios
|20 - 25||Normal|
|25 - 30||Overweight|
Reference standards have been developed to identify individuals at risk for being either over- or underweight. However, BMI can misclassify some large frame or muscular people as overweight. It is strictly a ratio and does not necessarily reflect percent body fat accurately. If you feel your BMI incorrectly categorizes you, have your percent body fat measured by a trained professional. Body fat can be determined from a variety of techniques including hydrostatic (underwater) weighing, or from skinfolds and circumference measures.
In addition to BMI, it is helpful to know your waist-to-hip ratio (WHR). This ratio determines your pattern of fat distribution, i.e., where you store body fat. The formula for calculating waist-to-hip ratio is:
Calculate Your Waist-to-Hip Ratio
Your WHR =----------------------------------------- ÷ ---------------------------------------- = ---------------
waist circumference (inches) hip circumference (inches)
Standards for Waist-to-Hip Ratios
< 0.95 < 0.80
The appropriate ratios for men and women are listed in Table. Ratios greater than these indicate a tendency toward central (torso) obesity. People who store excess fat centrally, as opposed to in their extremities, are at increased risk for cardiovascular (heart and blood vessel) diseases and diabetes. This chapter serves as an anchor around which the remaining chapters have been developed. In the following chapters you will learn sound nutritional practices and ways to enhance your physical performance. Importantly, you will see how good nutrition and a balanced exercise program together influence your physical fitness, military readiness, and ultimately your overall health.
Disclaimer: This website is for information purposes only. By providing the information contained herein we are not diagnosing, treating, curing, mitigating, or preventing any type of disease or medical condition. Before beginning any type of natural, integrative or conventional treatment regime, it is advisible to seek the advice of a licensed healthcare professional.