According to the ACSM, the optimal approach to weight loss combines mild caloric restriction with regular physical activity. Together these two strategies should provide a caloric deficit not to exceed 500 to 1000 calories per day. The physical activity component should manipulate exercise intensity and duration to burn from 300 to 500 calories per session and 1000 to 2000 calories per week.

Use of Calories

One of the obvious benefits of physical activity is that it burns calories. Calories are consumed according to body weight, so heavier people burn more calories per minute than lighter people for the same activity. To use it, multiply your body weight by the coefficient in the calories/min/lb column and then multiply this value by the number of minutes spent participating in the activity. For example, to determine the calories expended by a 170-pound person who walks at 4.5 mph for 30 minutes, do the following:

Body fat contains about 3500 calories per pound. Fat storage, however, which includes some lean support tissue muscle, connective tissues, blood supply, and other body components-represents approximately 2700 calories per pound. If this person performs this exercise daily, 1 pound will be lost in approximately 11 days or 33 pounds in 1 year, provided caloric intake is unchanged.

Aerobic exercises, such as walking and cycling, contribute significantly to weight loss. Minimal guidelines for maintaining fitness and losing weight require 300 calories per exercise session performed at least three times per week or 200 calories per session performed at least four times per week. Added weight loss can be accomplished by increasing the length of each exercise session and/or the number of sessions per week. High-intensity activities burn extra calories, but low-intensity exercises are recommended to prevent injury. Complete to determine the number of minutes that you should participate in your favorite activities to burn a minimum of 300 calories.

Deconditioned people should start slowly and gradually progress to using 300 to 500 calories per exercise session. For many people, low-intensity, long-duration physical activity, such as walking, is optimal. For weight loss, all calories do not have to be expended in one exercise session. Three 15 ­ minute walks in a day result in a substantial expenditure of energy. Any physical activity above the amount normally done in a day is a bonus for weight control. The cumulative effect of activities such as walking upstairs, mowing the lawn, and mopping floors can be combined with a structured exercise program to produce steady, safe weight loss.

Exercise Stimulates Metabolism

Basal metabolic rate (BMR) is the energy required to sustain life when the body is in a rested and fasted state. BMR is measured in calories and represents the energy needed to keep the heart, lungs, liver, kidneys, and all other organs functioning. More calories are used to maintain BMR than to perform any other function. Approximately 70% of the energy liberated from food is expended to support BMR.

Metabolism is affected by age, gender, nervous system activity, secretions from endocrine glands, nutritional status, sleep, fever, climate, body surface area, and amount of muscle tissue. Because men have more muscle tissue than women, their BMRs average 5% to 10% higher.

BMR declines with age, primarily because of the physical inactivity and muscle loss that often accompany aging. The annual decrease in BMR beginning at 25 or 30 years of age, though imperceptible, has serious ramifications for weight management and accounts for a significant amount of the weight gained with age. Authorities estimate that the loss of muscle tissue is equal to 3 % to 5 % every decade after age 25 to 30 years. The subsequent decline in BMR produces changes in body composition . Exercise and physical activities are the keys to weight management because they increase and/or sustain muscle tissue, thus accelerating metabolism and using calories.

The Key to Weight Control

Although scientifically controlled studies have not yet proven that physical activity is instrumental in losing weight, they provide compelling evidence as to its importance in weight control and weight loss maintenance. People who lose weight and keep it off almost always exercise daily. Studies that attempt to identify predictors of successful weight maintenance point to physical activity as one of the best markers for long-term success. Researchers at the University of California at Davis found that 90% of the women who had lost 20 pounds and kept it off for at least 2 years were avid exercisers; of the women who had regained the weight, only 35% were physically active. At the Baylor College of medicine in Houston, another group of researchers put 160 obese adults on one of three year-long weight loss programs: diet only, exercise only, or exercise and diet. Everyone lost weight. (The exercise and diet group lost the most). But 2 years later, the exercise-only participants were the only ones to keep the weight off. Other large-scale studies that follow men and women in weight-loss programs for 10 years consistently show that major weight gain is much more likely to occur in people who are sedentary than those who are physically active. Thus although physical activity as a singular strategy has modest effects on weight loss, it is the key strategy for lifelong weight control. More importantly, moderate exercise improves health and reduces risk factors associated with morbidity and mortality for the obese just as it does for normal-weight people.

Combining Dietary Modification and Exercise

Because caloric consumption and expenditure are involved in weight management, both should be manipulated to be effective. Combining sensible exercise and sensible changes in eating habits that can be maintained for life is the most effective approach to permanent weight management. Dieting alone can promote significant weight loss, but a substantial component of the weight loss may be lean tissue. Physical activity alone results in modest fat loss and an increase in lean body mass. Combination strategies involving both food restriction and physical activity meet the goals of weight management most effectively: it improves body composition by promoting weight loss, fat loss, and lean-tissue gain.

BeHavioral Effects

Some evidence suggests that obese people are more likely than normal-weight people to eat in response to external cues. A clock that says it is suppertime; media messages advertising food and beverages; and the sight, sound, and aroma of food are more apt to elicit eating behavior in the obese. This is the basis of the “externality” hypothesis: if people can learn to eat in response to external cues, they can also learn to recognize cues that stimulate eating behavior, substitute other behaviors for eating, and use techniques that decrease the amount of food eaten. As a result of this training the response to external cues should be reduced and replaced by attention to internal hunger signals. Many techniques have been developed over the past 20 years that may assist people in resisting the tendency to eat indiscriminately or to overeat. Generally these techniques employ one or more of the following approaches:

1. Self-monitoring: a journal or daily log is kept, recording food consumption, physical activities, and circumstances related to eating.
2. Control of precursors to eating: the events and circumstances that elicit eating and overeating are identified.
3. Control of eating: behavioral modification techniques are used to control, change, or modify specific eating behaviors.
4. Reinforcement through the use of rewards: rewards tied to the achievement of behavioral goals are identified and used.

These techniques may be useful to some people especially if they are combined with sensible food choices and exercise.

Diets very low in calories (800 calories per day or fewer), including those that have been promoted as having a “protein-sparing effect” (conserving lean tissue), have often been associated with serious medical complications, including cardiac dysrhythmias (irregular heart rate that is sometimes intractable) and sudden death. Diets very low in calories Produce distinctive and abnormal electrocardiographic (ECG) rhythm patterns that are most likely a used by protein loss from the myocardium (heart muscle) or cell-membrane instability from rapid Weight loss.Stringent dieting is also considered a major trigger for binge eating. A 6-month experiment of healthy men who were put on a diet that provided about one half of their usual daily caloric intake resulted in massive eating binges in which the men ate up to five meals and 5000 calories a day until they had returned to their normal weight.

Another problem with very-law-calorie diets is that they cause an adaptive response that decreases energy expenditure and increases fat storage. Repeated dieting may lower BMR on a long-term basis.

Low-Calorie Diets

Low-calorie diets (800 to 1000 calories per day) result in atrophy of the heart muscle. When low­calorie diets are accompanied by regular exercise, the muscle loss is minimized, but it still occurs. However, regular exercise combined with a moderate-calorie diet results in loss of body weight and gain of cardiac muscle. Exercise-induced cardiac hypertrophy results in a stronger, more efficient heart.

Low-Fat Diets

Low-fat diets are potentially effective techniques for losing weight. With its high-caloric yield, low thermic effect, and almost unlimited capacity for storage, fat is a major threat to weight maintenance. Consequently the current fixation is on “fat-free” or “low-fat” foods. The assumption is that if a food is low in fat, it is also low in calories. Only 7% of Americans are concerned about calories, compared with 60% who cite fat as public enemy number 1.27 As a result, although Americans are consuming less fat calories percentage-wise, they are consuming more total calories from all sources and are getting heavier. (Actual fat intake remains the same as it was during the past 10 years. Percentage-wise, it dropped from 36% to 34% because of an increase in total calories consumed. )

Low-fat diets have not been effective for many dieters because the dieters have become volume eaters. Researchers at Pennsylvania State University demonstrated this point when on separate days they gave women one of three types of yogurt: low fat, low calorie; low fat, high calorie; and high fat, high calorie. The low-fat, high-calorie and high-fat, high­calorie yogurts contained the same number of total calories. Half of these yogurts were labeled either low fat or high fat; the other half were unmarked. Thirty minutes after consuming the yogurt, the women ate lunch. The women who ate the yogurt labeled low fat compensated by taking in more calories during lunch even if they ate the low-fat, high­calorie version. The women who ate the unlabeled yogurt, on the other hand, ate fewer calories at lunch after eating the high-calorie version. The researchers concluded that when the women ate yogurt labeled low fat, they rationalized that they could indulge more at lunch. But when they were given unlabeled yogurt, they were more tuned in to their bodies’ physical cues and naturally adjusted the amount they ate.

The attitude that people can eat what they want, in unlimited quantities, as long as it’s fat free is wrong. Calories do count. Fat-free foods can help people lose weight if they are used properly, if they don’t result in over compensatory consumption of food, and if total calories are kept in line.

Popular Diets

Many diets on the market are nutritionally sound, and many are not. Some are potentially hazardous, and many are based on faulty nutritional and physiological concepts. Some require that food be eaten in a certain order and severely restrict allowable foods. Diets such as Jenny Craig come in pre measured servings. Some require medical supervision. Others impose unrealistic demands on caloric restrictions, and still others make promises based more on fantasy than facts. The Food and Drug Administration (FDA) does not investigate every new fad diet, and many diet plans are published without the FDA’s endorsement. If a diet is published, it is usually because a publisher sees potential profits from its sales. Publishers know that the advice to “eat less fat and increase physical activity” will not sell books but fad diets with secret ingredients or magic formulas will.

Because fad diets are unlikely to disappear, identifying some of the characteristics and marketing strategies used by diet promoters to appeal to unwitting consumers is helpful:

• They promote quick results.
• They stress eating one type of food to the exclusion of others.
• They emphasize gimmick approaches, such as eating food in a particular order.
• They cite anecdotes and testimonials, usually involving well-known people.
• They claim to be a panacea for everyone. They often promote a secret ingredient.
• They often recommend expensive supplements.
• They rarely emphasize permanent changes in eating habits.
• They usually show little concern for accepted principles of good nutrition . They are usually cynical of the evidence that comes from the scientific community.

In general, dieting is an ineffective weight­management method. The expectation that temporary changes in eating habits will lead to permanent weight loss is unrealistic. Sensible and permanent dietary changes that depend on wise food choices are an excellent way to cut calories and a healthy way to eat.

To maintain weight, caloric intake must be balanced by caloric expenditure. To lose weight an individual has to achieve a caloric deficit in which the number of calories burned exceeds the number of calories consumed. This is the basic principle of weight management. As such, it is simple, straight forward, and includes three obvious strategies -(1) Restricting caloric intake by dieting

(2) Increasing caloric expenditure through physical activity

(3) A combination of dieting and physical activity. What is not so easy to explain is how two people can respond so differently to dieting and exercise weight loss strategies. Complex forces, many of which are still not clearly understood, influence the success of weight-management/weight-loss efforts.

Dieting

Statistics show that dieting is the method of choice for most Americans trying to lose weight. Although dieting usually works only temporarily, most people who have failed to maintain weight loss are willing to try again. Many people seek the miraculous diet that will transform them from fat to thin, preferably with minimal effort and in the shortest time possible.

The success rate of diet only strategies is dismal. In its review of organized weight-loss programs, the NIB found that within 1 year dieters gained back between one third and two thirds of the lost weight; within 5 years they regained nearly all of it. 23 Only 5% of all dieters are successful in reducing to a target weight and maintaining that weight for more than 5 years. Maintaining post diet weight is one of the major failures of weight loss through dieting because dieters do not learn the habits and behaviors needed to remain at the new weight. As a result they lose and regain weight many times in their lives. This pattern of repeated weight loss and gain, known as weight cycling, yo-yo dieting, and seesaw approaches to weight loss, is potentially harmful and counterproductive.

In a review of the literature throughout 1991 on weight cycling, Wing 29 concluded that contrary to popular opinion there did not appear to be any negative effects of cycle dieting on total body fat, the distribution of fat, or metabolism. Subsequent efforts to lose weight also appeared to be unaffected. However, evidence suggests that weight cycling increases the risk of death, especially from cardiovascular conditions.

Researchers at Harvard University 30 studied data on 11,703 subjects over 30 years to see whether weight cycling had any effect on longevity. As expected, those whose weight remained stable had a lower mortality rate. However, those who lost weight were more likely to die than those who gained weight. Men who gained more than 11 pounds were 36% more likely to die than those whose weight remained stable. The men who lost more than 11 pounds, however, had a 57% higher chance of dying. The explanation proposed was that those who had lost 11 pounds over the decade had actually gained and lost an average of 100 pounds over their lifetimes. The stress of yo-yo dieting contributed to the higher death rates. However, with the high recidivism rate of dieters, the researchers concluded that it is probably better to remain slightly overweight than to weight cycle. Exceptions are people whose excessive body weight increases their risk for diabetes, high blood pressure, and high cholesterol levels. In a 1994 report of 43 studies on the effects of weight cycling, researchers concluded that the health gains from a weight loss of as little as 5 to 10 pounds, even if it is temporary, out­weighs the hazards of weight cycling for people with a history of these chronic conditions. Still, experts agree that it is better to lose weight and keep it off.