Metabolism is the process of breaking down food into fuel. An individual's metabolic rate is a quantitative measure of how fast the body digests food and burns calories through activity and muscular work. Because the muscles use 90 percent of the calories a person consumes, the more muscular tissue individuals have and the more active they are, the higher their metabolism. The greater the level of metabolism, the greater the caloric needs. As a consequence, highly active individuals can eat more food than sedentary individuals because they require more calories to fuel their muscles. Because athletes, for example, have a higher metabolism level, they tend to burn calories faster than inactive people.

How do calories and metabolism apply to weight loss? When individuals eat and burn the same number of calories daily, their energy level is balanced and an existing level of weight is maintained. By contrast, individuals gain weight when they eat more calories than they expend -- a situation many individuals find themselves in due to overindulgence and inactivity. If calorie consumption exceeds the amount of calories burned, individuals will gain fat. One approach to losing weight is to eat less, the other is to increase caloric expenditure through exercise. When individuals consume fewer calories than they use, their bodies will rely on stored fat and/or muscle to produce energy. Once they start using body fat or muscle for energy, they will begin to lose weight. For example, an energy deficit of 3,500 Calories will result in the loss of one pound.

The importance of maintaining blood sugar

If weight loss is this simple, why do so many individuals fail in their efforts to "win the losing game"? Unfortunately, many individuals try to lose weight by limiting their intake of fluids so they don't retain water weight. Water weight loss, however, won't cause a lasting change in body composition (the ratio of muscle to fat) and any weight lost will be regained almost immediately when fluids are ingested again.

Many dieters also reduce their caloric intake by either skipping meals or cutting back on their intake of carbohydrates, both of which cause their blood sugar levels to plummet. When blood sugar levels drop severely, the human body thinks it is starving. To protect itself from starvation, the body actually conserves fat. The longer the blood sugar level is low, the more efficient the body becomes at storing food as fat and holding onto existing fat.

If individuals severely restrict their intake of calories, their bodies will eventually burn muscle tissue to help supply energy. Because lean body mass (LBM) affects metabolic rate, using muscle for energy (and thereby losing it) causes an individual's metabolism level to fall, thereby actually slowing the rate of caloric expenditure. With a decreased metabolism rate, caloric needs decline proportionately. As a consequence, the process of losing weight and keeping it off becomes much more difficult. In addition, cutting calories without incorporating exercise into a weight-control program further depresses the metabolism level. Without the "boost" that exercise provides to the metabolic rate, individuals continue to burn calories more and more slowly, eventually resulting in plateaus.

After dieting for a while, what happens when individuals step on a scale? Often, they are lighter due, in large part, to the fact that they have lost water and muscle weight. They have, however, lost very little fat weight. It is important to remember that weight loss is not necessarily fat loss. Although individuals may appear to be lighter, they actually may be proportionally fatter.

This area of misplaced optimism is the point where many dieters go wrong. In their excitement about achieving a lower number on the scale, they immediately and incorrectly assume that they have lost fat. Instead, they may have set themselves up for failure (not being able to keep the weight off) by metabolizing LBM instead of fat. In the process, they have also lowered their resting metabolic rate. To lose weight and keep it off, the focus must be on losing fat -- not muscle.

Losing the right "weight"

Because restrictive diets don't produce long-lasting results, they should be shunned forever. No matter how appealing, almost all diets are doomed to eventually fail. How can a person lose weight without following a strict diet? Successful weight control begins with a lifetime commitment to nutritionally sound, balanced eating habits and a physically active lifestyle.

Before trying to lose weight, individuals should abandon the idea that their weight-control efforts will involve temporary measures. To lose weight and keep it off, permanent changes in eating and physical activity habits must be made. Although this approach may sound intimidating, the benefits of such a lifestyle change (improved health, more energy, better self-esteem, a lower risk of developing a wide variety of medical conditions, an enhanced quality of life, etc.) far outweigh the costs.

Making a long-term commitment to weight control often involves behavioral changes. While many theories exist about how to properly change personal behavior, the process essentially involves substituting unhealthy behaviors with healthy, well-established habits. Such a process takes time. The best way to approach the task is to identify the elements of eating and exercise habits that need to be changed, and then institute programs to affect that change -- taking small steps at a time.

To develop habit awareness, most experts recommend keeping a diary to determine what specific behavior(s) contributed to the present weight problem. Individuals should keep a journal for a week to record all food and beverages consumed, every physical activity performed (e.g., walked up four flights of stairs, washed and folded three loads of laundry, stood on their feet seven hours at work, exercised for 20 minutes), and the times of day they ate and were physically active. Such information may be helpful in identifying how to expand the total amount of time spent on exercise or how to eliminate extracurricular eating (snacking).

After a week, individuals should carefully review the information in their diaries or take them to qualified professionals for help. A registered dietitian, for example, can help analyze nutrient and caloric intake, identify triggers that may stimulate eating (e.g., coffee breaks, television and restaurants) and evaluate overall levels of energy expenditure. If the diary shows that they are eating a lot of high-fat foods such as doughnuts, french fries and chocolate, the necessary adjustments can be made in eating habits. By the same token, if their diary points out that they tend to nibble endlessly while watching television, they can either change their environment (make food less accessible and find something else to do while watching TV) or change their leisure habits to reduce the amount of time spent watching television. Finally, diaries may show that they're far too inactive to achieve their weight-control goals. For example, if they sit at a desk all day and then spend evenings on the couch, they'll never be able to lose the desired pounds of fat weight and keep them off.

Developing a plan and putting it into action

If an individual's goal is to take off and keep off unwanted fat weight, that person must eat sensibly and exercise regularly. Knowing what constitutes a sensible diet and a sound exercise program is critical to achieving maximum results.

Eat Sensibly. A sound diet for weight reduction will be relatively low in calories and still provide all of the nutrients essential to normal body functioning. It will contain foods that appeal to individual taste and can be easily incorporated into an individual's lifestyle. According to the American Dietetic Association, a diet should never fall below a level of approximately 10 to 12 Calories per pound of body weight. A sensible diet must foster new, healthier eating habits (e.g., limiting fat consumption, avoiding fried foods, reducing salt intake) that can be maintained over the long haul.

One of the first steps in deciding what to eat is to determine how much food (calorie-wise) should be consumed to cause fat loss. The simplest way to calculate daily caloric intake needs is to multiply an individual's present weight (in pounds) by 15 Calories (12 Calories to meet the minimum basal needs, plus three Calories to account for the energy needed to support a physically active lifestyle). For example, a 150-pound individual needs 2,250 Calories daily to sustain current body weight. The next step is to reduce the daily maintenance total by 250 Calories -- the amount necessary to achieve a one-pound weight loss per week when it's combined with an exercise program that burns an additional 250 Calories a day (fielding a net negative caloric balance of 500 Calories daily). Because one pound of body fat has 3,500 Calories, the individual will lose one pound a week (7 times 500 = 3,500) -- a moderate rate of loss that is more likely to be sustained than a "quick-fix" approach.

Accordingly, if a person maintains a calorie intake of 2,000 Calories daily, that individual will lose one pound each week. Although decreasing caloric intake by only 250 Calories (the equivalent of eliminating one slice of pizza from a person's diet daily) may not seem like much, research suggests that more drastic reductions may have negative, long-term consequences. For example, if caloric intake is reduced too dramatically, there would not be sufficient energy to support an active lifestyle, and the chances of sticking to a stringent eating regimen are typically very low. Over time, extremely large cuts in caloric intake may cause the body to metabolize muscle tissue instead of fat. As a guideline, the American Dietetic Association recommends that daily caloric intake should never fall below 1,000 to 1,200 Calories for normal, healthy adults.

Once it has been established how much individuals should eat to achieve their weight-control goals, the next step is to identify what to eat. The ideal "weight-control" diet should be high in complex carbohydrates and low in fat. The following are helpful, practical steps individuals can take to positively restructure their eating habits:

* Limit servings to one portion. Have all meals served on a plate in the kitchen, not family-style at the table. After taking one portion, wrap up and store leftovers immediately to discourage nibbling. Have all meals served on small plates so it doesn't look as if food consumption is being restricted.

* Eat slowly. Take small bites, chew food longer and put down utensils between bites. It takes at least 20 minutes for the satiety center in the brain to trigger a feeling of fullness. By that time, most people have finished the first helping and are beginning seconds.

* Forget about being a committed member of the "clean-plate club" -- stop eating when full. Try to focus only on eating during a meal. Break any habits that may encourage overeating (e.g., eating while reading or watching television).

* Keep high-fat foods out of the house. If other people in the house insist on having high-fat items, at least try to keep them out of sight to reduce temptation. Likewise, don't keep dishes of candy, nuts or other treats in a convenient place.

One final factor relating to sensible eating involves frequency of meals. How often individuals eat can impact whether they compromise their commitment to eating sensibly. By eating frequently and, thereby, maintaining stable blood sugar levels, an individual can prevent (or at least minimize) the onset of those hunger pangs that often drive even the most well-intentioned individual to snack or binge. Research suggests that if individuals want to maintain balanced levels of blood sugar, they should eat at least three regular meals or five to six mini-meals daily. Skipping meals or eating almost all daily calories in one meal can hinder or minimize reductions in body fat.

Exercise Regularly. Eating sensibly is only one component of a sound weight-control program. For successful, lifelong weight control, sensible eating and regular exercise go hand-in-hand. The more an individual exercises on a regular basis, the faster that individual's body will burn calories. In addition, strength-training exercise can either help to build muscle tissue or, at a minimum, to counter the tendency for a severely calorie-restricted diet to cause a significant loss of muscle. Also, exercise can improve physical appearance, even if a significant amount of weight is not lost. Because muscle is more dense than fat, individuals can look more fit and trim without changing total-body weight. While a personally enjoyable physical activity will help to promote some degree of weight loss, an exercise program that combines aerobic conditioning and strength training represents the best approach for using exercise to control body composition.

A case study

A 40-year-old secretary, is 5 feet 3 inches and weighs 140 pounds. She has 30 percent body fat and lives a sedentary lifestyle, although she is a member of a local health/fitness club. Her diet log shows that she usually skips breakfast or grabs a doughnut and coffee with cream. She drinks coffee all morning to keep her going. Lunch and dinner are often high-fat selections from fast-food restaurants. Her assessed need for daily caloric intake is about 2,100 Calories (140 times 15 Calories).

She wants to reduce her body weight by 25 pounds to reach a weight of 115 pounds. However, a body weight of 125 pounds happens to be the lowest weight that she has been able to achieve and maintain (as an adult) for a period of six months or more.

She reduces her intake of Calories by 250 for a daily total of 1,850. She starts eating a breakfast of water or juice, a bagel, fruit and/or cereal, and limits herself to two cups of coffee each morning. To avoid going to fast-food restaurants, Overwaite brings her lunch to work and carries lean-meat sandwiches on whole grain bread, fruit, soups, pretzels, salads, and water, iced tea or juice. For dinner, she tries to prepare meals each weekend to freeze for week nights. This way, Overwaite can quickly warm pasta, chicken breasts or fish. To stay away from the vending machine, she stashes snacks at her desk, including dry cereal, fruit, cut-up vegetables and graham crackers. At home, she now has skim milk, fat-free salad dressings, low-fat cheeses and reduced-fat crackers. Occasionally, she will satisfy her sweet tooth with frozen yogurt.

She begins a daily exercise program at her health/fitness club. Three days a week, she exercises on either a stair-climbing machine or an elliptical striding machine for 20 minutes, followed by a five-minute workout on an upper-body machine. Two days a week, she works out on a recumbent cycle and completes a five-machine strength circuit (chest press, lat row, leg press, shoulder press, lat pull-down) for 30 minutes combined.

* Ten weeks into her program she has lost 15 pounds, and her current body weight is now 125 pounds. She feels energized, looks better, and is motivated to maintain her new healthy eating and exercise habits.

A winning game plan

The most appropriate approach for achieving permanent weight loss is a sensible diet combined with a program of sound exercise that includes both aerobic conditioning and strength training. While such a weight-control "game plan" may not produce as rapid a weight loss as the more popularly promoted, very low-calorie diets it will provide individuals with a medically sound and effective strategy for "winning the losing game." Almost without exception, very low-calorie diets, largely as a result of their detrimental effects on resting metabolic rates, set individuals up for weight regain and, in their eyes, failure. A sensible diet/exercise approach to weight reduction tends to produce a rate of weight loss of about 1 to 2 pounds per week (the rate recommended by most experts). Although it might take longer for individuals to reach their desired weight-control goals, any weight lost in this manner tends to be truly lost, not momentarily misplaced.

REFERENCES

American College of Sports Medicine. ACSM's Exercise Management for Persons with Chronic Diseases and Disabilities. Human Kinetics: Champaign, Ill, 1997.

American College of Sports Medicine. ACSM's Resource Manual for Guidelines for Exercise Testing and Prescription, 3rd ed. Williams & Wilkins: Baltimore, Md., 1998.

American College of Sports Medicine. Position Statement on Proper and Improper Weight Loss Programs. Medicine and Science in Sports and Exercise, 15(l):9, 1983.

Anderson, R., K.D. Brownell and W.L. Haskell. The Health & Fitness Club Leader's Guide. American Health Publishing Co.: Dallas, Texas, 1992.

Bryant, C.X. and J.A. Peterson. Weight loss: Unfolding the truth. Fitness Management, 10(6):42-44, 1994.

Clark, N. Nancy Clark's Sports Nutrition Guidebook, 2nd ed. Human Kinetics: Champaign, Ill., 1990.

Nieman, D.C. The Exercise-Health Connection. Human Kinetics: Champaign, Ill., 1998.

Nieman, D.C. Fitness and Sports Medicine: An Introduction, 2nd ed. Bull Publishing Co.: Palo Alto, Calif., 1990.

Peterson, J.A. and C.X. Bryant (eds). StairMaster Fitness Handbook, 2nd ed. Sagamore Publishing Co. Inc.: Champaign, Ill., 1995.

Porcari, J.P. Fat-burning exercise: Fit or farce. Fitness Management, 10(8):40-41, 1994.

ACKNOWLEDGEMENT
The authors wish to thank Julie E. Mullen, M.S., for her valuable contributions to this article.



James Peterson, Ph.D., FACSM, is a sports medicine consultant, fellow of the American College of Sports Medicine, a former faculty member at the United States Military Academy and a former director of sports medicine for StairMaster Sports/Medical Products Inc.
 

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