INTRODUCTION

PHYSICAL ACTIVITYTABLE 4-1. Benefits of Physical Activity.TABLE 4-The most important component of an effective weight-management program must be the prevention of unwanted weight gain from excess body fat. The military is in a unique position to address 

prevention from the first day of an individual's military career. Because the military population is selected from a pool of individuals who meet specific criteria for body mass index (BMI) and percent body fat, the primary goal should be to foster an environment that promotes maintenance of a healthy body weight and body composition throughout an individual's military career. There is significantsignificant evidence that losing excess body fat is difficult for most individuals and the risk of regaining lost weight is high. From the first day of initial entry training, an understanding of the fundamental causes of excess weight gain must be communicated to each individual, along with a strategy for maintaining a healthy body weight as a way of life.

The principle of weight gain is audifort  simple: energy intake exceeds energy expenditure. However, as discussed in Chapter 3, overweight and obesity are clearly the result of a complex set of interactions among genetic, behavioral, and environmental factors. While hundreds, if not thousands, of weight-loss strategies, diets, potions, and devices have been offered to the overweight public, the multi-factorial etiology of overweight challenges practitioners, researchers, and the overweight themselves to identify permanent, effective strategies for weight loss and maintenance. The percentage of individuals who lose weight and successfully maintain the loss has been estimated to be as small as 1 to 3 percent (Andersen et al., 1988; Wadden et al., 1989).

Evidence shows that genetics plays a role in the etiology of overweight and obesity. However, genetics cannot account for the increase in overweight observed in the U.S. population over the past two decades. Rather, the behavioral and environmental factors that conspire to induce individuals to engage in too little physical activity and eat too much relative to their energy expenditure must take most of the blame. It is these factors that are the target of weight-management strategies. This chapter reviews the efficacy and safety of strategies for weight loss, as well as the combinations of strategies that appear to be associated with successful loss. In addition, the elements of successful weight maintenance also will be reviewed since the difficulty in maintaining weight loss may contribute to the overweight problem. A brief discussion of public policy measures that may help prevent overweight and assist those who are trying to lose weight or maintain weight loss is also included.

Increased physical activity is an essential component of a comprehensive weight-reduction strategy for overweight adults who are otherwise healthy. One of the best predictors of success in the long-term management of overweight and obesity is the ability to develop and sustain an exercise program (Jakicic et al., 1995, 1999; Klem et al., 1997; McGuire et al., 1998, 1999; Schoeller et al., 1997). The availability of exercise facilities at military bases can reinforce exercise and fitness programs that are necessary to meet the services' physical readiness needs generally, and for weight management specifically. For a given individual, the intensity, duration, frequency, and type of physical activity will depend on existing medical conditions, degree of previous activity, physical limitations, and individual preferences. Referral for additional professional evaluation may be appropriate, especially for individuals with more than one of the above extenuating factors. The benefits of physical activity (see Table 4-1) are significant and occur even in the absence of weight loss (Blair, 1993; Kesaniemi et al., 2001). It has been shown that one of the benefits, an increase in high-density lipoproteins, can be achieved with a threshold level of aerobic exercise of 10 to 11 hours per month.

Benefits of Physical Activity.

For previously sedentary individuals, a slow progression in physical activity has been recommended so that 30 minutes of exercise daily is achieved after several weeks of gradual build-up. This may also apply to some military personnel, especially new recruits or reservists recalled to active duty who may be entering service from previously very sedentary lifestyles. The activity goal has been expressed as an increase in energy expenditure of 1,000 kcal/wk (Jakicic et al., 1999; Pate et al., 1995), although this quantity may be insufficient to prevent weight regain. For that purpose, a weekly goal of 2,000 to 3,000 kcal of added activity may be necessary (Klem et al., 1997; Schoeller et al., 1997). Thus, mental preparation for the amount of activity necessary to maintain weight loss must begin while losing weight (Brownell, 1999).

For many individuals, changing activity levels is perceived as more unpleasant than changing dietary habits. Breaking up a 30-minute daily exercise “prescription” into 10-minute bouts has been shown to increase compliance over that of longer bouts (Jakicic et al., 1995, Pate et al., 1995). However, over an 18-month period, individuals who performed short bouts of physical activity did not experience improvements in long-term weight loss, cardiorespiratory fitness, or physical activity participation in comparison with those who performed longer bouts of exercise. Some evidence suggests that home exercise equipment (e.g., a treadmill) increases the likelihood of regular exercise and is associated with greater long-term weight loss (Jakicic et al., 1999). In addition, individual preferences are paramount considerations in choices of activity.

When strength training or resistance exercise is combined with aerobic activity, long-term results may be better than those with aerobics alone (Poirier and Despres, 2001; Sothern et al., 1999). Because strength training tends to build muscle, loss of lean body mass may be minimized and the relative loss of body fat may be increased. An added benefit is the attenuation of the decrease in resting metabolic rate associated with weight loss, possibly as a consequence of preserving or enhancing lean body mass.

As valuable as exercise is, the existing research literature on overweight individuals indicates that exercise programs alone do not produce significant weight loss in the populations studied. It should be emphasized, however, that a large number of such studies have been conducted with middle-aged Caucasian women leading sedentary lifestyles. The failure of exercise alone to produce significant weight loss may be because the neurochemical mechanisms that regulate eating behavior cause individuals to compensate for the calories expended in exercise by increasing food (calorie) intake. While exercise programs can result in an average weight loss of 2 to 3 kg in the short-term (Blair, 1993; Pavlou et al., 1989a; Skender et al., 1996; Wadden and Sarwer, 1999), outcome improves significantly when physical activity is combined with dietary intervention. For example, when physical activity was combined with a reduced-calorie diet and lifestyle change, a weight loss of 7.2 kg was achieved after 6 months to 3 years of follow-up (Blair, 1993). Physical activity plus diet produces better results than either diet or physical activity alone (Blair, 1993; Dyer, 1994; Pavlou et al., 1989a, 1989b; Perri et al., 1993). In addition, weight regain is significantly less likely when physical activity is combined with any other weight-reduction regimen (Blair, 1993; Klem et al., 1997). Continued follow-up after weight loss is associated with improved outcome if the activity plan is monitored and modified as part of this follow-up (Kayman et al., 1990).

While studies have shown that military recruits were able to lose significant amounts of weight during initial entry training through exercise alone, the restricted time available to consume meals during training probably contributed to this weight loss (Lee et al., 1994).

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BEHAVIOR AND LIFESTYLE MODIFICATION
Self-Monitoring and Feedback
Other Behavioral Techniques
Eating Environments
1.

The use of behavior and lifestyle modification in weight management is based on a body of evidence that people become or remain overweight as the result of modifiable habits or behaviors (see Chapter 3), and that by changing those behaviors, weight can be lost and the loss can be maintained. The primary goals of behavioral strategies for weight control are to increase physical activity and to reduce caloric intake by altering eating habits (Brownell and Kramer, 1994; Wilson, 1995). A subcategory of behavior modification, environmental management, is discussed in the next section. Behavioral treatment, which was introduced in the 1960s, may be provided to a single individual or to groups of clients. Typically, individuals participate in 12 to 20 weekly sessions that last from 1 to 2 hours each (Brownell and Kramer, 1994), with a goal of weight loss in the range of 1 to 2 lb/wk (Brownell and Kramer, 1994). In the past, behavioral approaches were applied as stand-alone treatments to simply modify eating habits and reduce caloric intake. However, more recently, these treatments have been used in combination with low-calorie diets, medical nutrition therapy, nutrition education, exercise programs, monitoring, pharmacological agents, and social support to promote weight loss, and as a component of maintenance programs.

Self-monitoring of dietary intake and physical activity, which enables the individual to develop a sense of accountability, is one of the cornerstones of behavioral treatment. Patients are asked to keep a daily food diary in which they record what and how much they have eaten, when and where the food was consumed, and the context in which the food was consumed (e.g., what else they were doing at the time, what they were feeling, and who else was there). Additionally, patients may be asked to keep a record of their daily physical activities. Self-monitoring of food intake is often associated with a relatively immediate reduction in food intake and consequent weight loss (Blundell, 2000; Goris et al., 2000). This reduction in food intake is believed to result from increased awareness of food intake and/or concern about what the dietitian or nutrition therapist will think about the patient's eating behavior. The information obtained from the food diaries also is used to identify personal and environmental factors that contribute to overeating and to select and implement appropriate weight-loss strategies for the individual (Wilson, 1995). The same may be true of physical activity monitoring, although little research has been conducted in this area. Self-monitoring also provides a way for therapists and patients to evaluate which techniques are working and how changes in eating behavior or activity are contributing to weight loss. Recent work has suggested that regular self-monitoring of body weight is a useful adjunct to behavior modification programs (Jeffery and French, 1999).

Some additional techniques included in behavioral treatment programs include eating only regularly scheduled meals; doing nothing else while eating; consuming meals only in one place (usually the dining room) and leaving the table after eating; shopping only from a list; and shopping on a full stomach (Brownell and Kramer, 1994).

Reinforcement techniques are also an integral part of the behavioral treatment of overweight and obesity. For example, subjects may select a positively reinforcing event, such as participating in a particularly enjoyable activity or purchasing a special item when a goal is met (Brownell and Kramer, 1994).

Another important component of behavioral treatment programs may be cognitive restructuring of erroneous or dysfunctional beliefs about weight regulation (Wing, 1998). Techniques developed by cognitive behavior therapists can be used to help the individual identify specific triggers for overeating, deal with negative attitudes towards obesity in society, and realize that a minor dietary infraction does not mean failure. Nutrition education and social support, discussed later in this chapter, are also components of behavioral programs.

Behavioral treatments of obesity are frequently successful in the short-term. However, the long-term effectiveness of these treatments is more controversial, with data suggesting that many individuals return to their initial body weight within 3 to 5 years after treatment has ended (Brownell and Kramer, 1994; Klem et al., 1997). Techniques for improving the long-term benefits of behavioral treatments include: (1) developing criteria to match patients to treatments, (2) increasing initial weight loss, (3) increasing the length of treatment, (4) emphasizing the role of exercise, and (5) combining behavioral programs with other treatments such as pharmacotherapy, surgery, or stringent diets (Brownell and Kramer, 1994).

Recent studies of individuals who have achieved success at long-term weight loss may offer other insights into ways to improve behavioral treatment strategies. In their analysis of data from the National Weight Control Registry, Klem and coworkers (1997) found that weight loss achieved through exercise, sensible dieting, reduced fat consumption, and individual behavior changes could be maintained for long periods of time. However, this population was self-selected so it does not represent the experience of the average person in a civilian population. Because they have achieved and maintained a significant amount of weight loss (at least 30 lb for 2 or more years), there is reason to believe that the population enrolled in the Registry may be especially disciplined. As such, the experience of people in the Registry may provide insight into the military population, although evidence to assert this with authority is lacking. In any case, the majority of participants in the Registry report they have made significant permanent changes in their behavior, including portion control, low-fat food selection, 60 or more minutes of daily exercise, self-monitoring, and well-honed problem-solving skills.

A significant part of weight loss and management may involve restructuring the environment that promotes overeating and underactivity. The environment includes the home, the workplace, and the community (e.g., places of worship, eating places, stores, movie theaters). Environmental factors include the availability of foods such as fruits, vegetables, nonfat dairy products, and other foods of low energy density and high nutritional value. Environmental restructuring empha-sizes frequenting dining facilities that produce appealing foods of lower energy density and providing ample time for eating a wholesome meal rather than grabbing a candy bar or bag of chips and a soda from a vending machine. Busy lifestyles and hectic work schedules create eating habits that may contribute to a less than desirable eating environment, but simple changes can help to counter-act these habits.

Commanders of military bases should examine their facilities to identify and eliminate conditions that encourage one or more of the eating habits that promote overweight. Some nonmilitary employers have increased healthy eating options at worksite dining facilities and vending machines. Although multiple publications suggest that worksite weight-loss programs are not very effective in reducing body weight (Cohen et al., 1987; Forster et al., 1988; Frankle et al., 1986; Kneip et al., 1985; Loper and Barrows, 1985), this may not be the case for the military due to the greater controls the military has over its “employees” than do nonmilitary employers.


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