ENERGY NEEDS OF THE BODY

What are our energy needs? How many calories should we consume (or burn) to achieve a healthy weight?  Although there are rough estimates for college-aged men (2500 to 3300 calories daily) and women (approximately 2500 calories daily), we all vary in our specific energy needs.  These needs are based on three factors: (1) basal metabolic rate (also referred to as resting energy expenditure, or FREE), (2) activity requirements, and (3) the thermic effect of food.

Basal Metabolism

Of the three factors that determine energy needs, basal metabolism uses the highest proportion (50% to 70%) of the total calories required by each person.  Basal Metabolic Rate (BMR) is a measure of resting energy expenditure that is taken upon awakening, 10-12 hours after eating, or 12-18 hours after significant physical activity.  A closely related construct, resting metabolic rate (RMR), is often used interchangeably with BMR.  In comparison with the BMR, the RMR is measured at rest, without the stringent control on physical activity required as with measuring BMR.  RMR measures the calories needed for functioning such as blood circulation, respiration, brain activity, muscle function, body temperature, and heartbeat.

Basal metabolism changes as people age.  For both males and females, the BMR is relatively high at birth and continues to increase until the age of 2.  Except for a slight rise at puberty, the BMR will then gradually decline throughout life.  If people fail to recognize that their BMR decreases as they grow older (2% per decade), they might also fail to adjust their food intake and activity level accordingly.  Thus they may gradually put on unwanted pounds as they grow older.

Activity Requirements

Each person’s caloric activity requirements vary directly according to the amount of their daily physical activity.  For example, sedentary office workers require a smaller daily caloric intake than construction workers, lumberjacks, or farm workers do.

Physical activity that occurs outside the workplace also increases caloric needs.  Sedentary office workers may be quite active in their recreational pursuits.  Active employees may spend their off hours lounging in front of the TV.  It’s important to closely examine the total amount of work or activity an individual engages in to accurately estimate that person’s caloric requirements.  Physical activity uses 20% to 40% of caloric intake.

Thermic Effect of Food

Thermic effect of food (TEF) refers to the amount of energy our bodies require for the digestion, absorption, and transportation of food.  This energy breaks down the bonds that hold complex food molecules together, resulting in smaller nutritional units that can be distributed throughout the body.  The amount of TEF burned varies for different types of food, with some food such as fat requiring less energy to convert to energy stores and others such as protein and carbohydrates requiring more.  The TEF peaks in about 1 hour after eating and accounts for approximately 10% of total energy expenditure.

Lifetime Weight Control

Obesity and frequent fluctuation in weight are thought to be associated with higher levels of morbidity and mortality.  So it is highly desirable to maintain your weight and body composition at or near optimum levels.  Although this may be a difficult goal to achieve, it is not unrealistic when practiced on a consistent basis.  The following are some keys to success:

·         Exercise: caloric expenditure through regular exercise, including cardiovascular exercise and strength training, is a key to maintain a healthy weight and body composition.

·         Dietary modification: plan meals around foods that have moderate levels of fat and are low in total fat and saturated fat and high in complex carbohydrates.  Many nutritionists are concerned about the safety of high-fat diets and ultra-low-fat diets for long-term weight management.

·         Lifestyle support: in addition to committing yourself to a lifestyle that features regular physical activity and careful food choices, build a support system that will nurture your efforts.  Inform your family, friends, classmates, and coworkers that you intend to rely on them for support and encouragement.

·         Problem solving: reevaluate your current approaches to dealing with stressors.  Replace any reliance on food as a coping mechanism with nonfood options, such as exercise or talking with friends or family members.

·         Redefinition of health: think about health and wellness in a manner that reinforces the importance of prevention and self-care, rather than waiting to become sick incapacitated before paying attention to your diet and activity level.

These suggested lifestyle choices will make a significant contribution to preventing a weight problem later.