THE CHALLENGE OF WEIGHT LOSS MAINTENANCE
Poor weight maintenance has been described as the "Achilles heel" of behavioral weight loss treatment programs. Typically, patients in these programs lose about 7% to 10% of their initial body weight after receiving 6 to 12 months of treatment, but subsequently experience gradual weight regain until stabilizing 12 to 18 months later at about 5% below their starting weight (6). A 5% weight loss is associated with reduced risk of type 2 diabetes and improvement in multiple cardiometabolic risk factors (5).
Efforts to maintain a reduced body weight may be opposed by certain physiological adaptations (e.g., decreases in resting metabolic rate, changes in hormones that affect appetite). Psychological, behavioral, and socioenvironmental factors also may serve as barriers to successful weight loss maintenance. For example, certain individuals may have more difficulty adhering to a regular physical activity regimen or a restricted diet given greater susceptibility to competing rewards associated with sedentary behaviors and palatable foods. In addition, initial benefits (e.g., weight loss, health benefits, improved appearance) obtained from initiating changes in diet and activity patterns may be eventually outweighed by the costs (e.g., effort, time) required to sustain such changes. Finally, effective regulation of body weight is particularly challenging within the context of an obesogenic environment characterized by maximum convenience, high accessibility to energy-dense foods, and city/neighborhood structures that limit opportunities for physical activity (3).
Despite the numerous obstacles to losing weight and keeping it off, it is estimated that one fifth of overweight and obese individuals in the United States have successfully lost weight and maintained their weight loss (13). Consequently, studying this group of "successful losers" serves as one way to learn how to better maintain weight loss in most individuals for whom this goal remains elusive.
THE NATIONAL WEIGHT CONTROL REGISTRY
The National Weight Control Registry (NWCR) was founded in 1994 by Rena Wing, Ph.D., director of the Weight Control and Diabetes Research Center of the Warren Alpert Medical School of Brown University, and James O. Hill, Ph.D., director of the Center for Human Nutrition of the University of Colorado, to answer two important questions about weight control: 1) Are there individuals who are successfully maintaining a substantial weight loss? 2) What are the characteristics and strategies that have helped these individuals to experience success?
In the last 15 years, the NWCR has made significant progress toward answering these questions by assessing weight, eating behavior, physical activity, and other health-related psychosocial and behavioral factors in more than 6,000 successful weight losers. To be eligible for the study, participants must be 18 years or older and have lost and maintained a minimum of 30 lbs (representing a minimum 10% weight loss for most overweight and obese individuals) for at least 1 year.
CHARACTERISTICS OF SUCCESSFUL WEIGHT LOSS MAINTAINERS
NWCR members tend to be female (77%), white (95%), middle-aged (mean, 47.0 years old; SD, 12.2), married (64%), and college educated (82%) (4). The average duration of weight loss maintenance at enrollment is 5.5 years. Recent entrants to the NWCR (i.e., between 2001 and 2004) reflect an increased proportion of men (28.7%) and older individuals, but the representation of ethnic minorities has not changed (11). Because the NWCR is a relatively homogeneous group of individuals who volunteered to share information about their weight and behaviors, caution should be used when attempting to generalize the findings to other populations, especially because of evidence suggesting that some minority groups may exhibit different behaviors and weight maintenance outcomes. For this reason, efforts to diversify the NWCR by recruiting more ethnic minorities are ongoing.
Over time, NWCR enrollees are reporting higher maximum lifetime weights, but also larger weight losses (11). Averaging across all years of the study, participants' average body mass index (BMI) before weight loss was 36.7 kg m−2 (SD, 8.5), and most (81.3%) participants were obese (i.e., BMI, ≥30). Upon entry into the NWCR, participants report an average weight loss of 33.6 kg (SD, 17.7), which had been maintained for 5.2 years (SD, 6.8), placing most participants in the normal weight (57.9%) or overweight range (29.9%), with only a small proportion of participants remaining obese (12.2%). Nearly 20% of NWCR members have lost 100 lbs (45.4 kg) or more.
MOTIVATIONS FOR WEIGHT LOSS
Efforts have been made nationwide to educate the public about obesity and its associated health consequences. Despite this outpouring of knowledge and education, only a minority of obese individuals will undertake and achieve a substantial weight loss (6). The NWCR has been used to investigate factors that led to the successful weight loss attempt of registry members in the hopes that these factors may be used to motivate weight loss in other obese individuals. Most (77%) members of the NWCR are able to identify a triggering event for their successful weight loss, including most commonly medical triggers (e.g., the onset of a weight-related health condition such as diabetes, sleep apnea, fatigue, and joint pain) and emotional triggers (e.g., being teased about being overweight) (4).
Notably, most (91%) NWCR members report a history of previous weight loss attempts. Among those with a previous weight loss history, the mean lifetime loss is 269.6 ± 217.3 lbs (4), which is accrued across multiple attempts, followed by periods of regain. Compared with previous (presumably unsuccessful) attempts, participants report having greater social, health reasons, or both for losing weight during their successful attempt. A greater commitment to making behavioral changes and use of more intensive approaches also is common during the successful attempt. These findings suggest that NWCR members make multiple weight loss attempts and frequently experience regain before achieving long-term maintenance of a substantial weight loss. This may be of some comfort to individuals who struggle with weight maintenance, as a history of previous attempts does not appear to preclude success in the long-term. Furthermore, the likelihood of success may be increased by enhancing commitment and adherence to behavioral strategies.
WEIGHT LOSS METHODS IN THE NWCR
Almost all members of the NWCR (89%) use some combination of diet and physical activity to achieve their weight loss (4). Only 10% use dietary strategies alone, and only 1% rely solely on exercise. Most participants use only one or two types of exercise during their weight loss attempt. The most common types of physical activity include walking, aerobic dancing, strength training, competitive sports, and swimming. Exercising at home is very common during the successful weight loss attempt (92%), as is exercising with a friend (40%) or in a group (31%).
Participation in a formal weight loss program is common, especially among women, whereas men are more likely to lose the weight on their own. The most frequently practiced dietary strategies for weight loss include restricting intake of certain types of foods such as those high in fat and sugar (87.6%), limiting the amount of food consumed (44.2%), and counting calories (43.7%) (4). The use of liquid formula (20%) and weight loss medication (6.2%) is less common, and surgery (2.4%) is rare.
WEIGHT MAINTENANCE METHODS IN THE NWCR
The NWCR has been used to identify common behavioral characteristics of successful weight losers (1,4). Of these, the high level of physical activity reported by NWCR members is perhaps the most striking. Participants report expending 2,571 ± 2,080 kcal week−1 in physical activity (the equivalent of walking 41 km week−1) on questionnaires completed at entry to the NWCR. These subjective measures suggest that men more often participate in high-intensity activities (e.g., running) and also expend about 370 kcal week−1 more than women. In addition to gender, participation in more intensive exercise is associated with lower age, a larger initial weight loss, lower body weight, and being unmarried or never married.
A total of 75% of participants report expending more than 1,000 kcal week−1 in physical activity. About one half (54%) of participants expend more than 2,000 kcal week−1, meeting the 2009 American College of Sports Medicine (ACSM) physical activity recommendation for long-term maintenance of weight loss. However, only 34% of registry members report meeting the 2005 Dietary Guidelines for Americans recommendation that weight-reduced adults engage in the equivalent of 3,000 kcal week−1 of activity.
Walking is one of the most popular forms of exercise, with 52.2% of registry members using this form of physical activity at least weekly. Other common activities include stationary and/or road cycling, aerobics, walking or running on a treadmill, weightlifting, running or jogging, stair stepper use, and step aerobics. Over time, the use of strength training has increased, which is now practiced by approximately 29% of NWCR members.
The high levels of self-reported physical activity among NWCR members are further supposed by a recent study that used an objective measure to examine physical activity levels in a similar cohort of successful weight loss maintainers (WLMs) (9). Using the RT3 triaxial accelerometer, Phelan and colleagues compared daily physical activity amount and intensity in 135 WLM who successfully reduced their weight from obese to normal and 102 always normal weight (NW) individuals. WLMs engaged in more vigorous intensity physical activity per day than NWs (24.4 ± 22.5 minutes day−1 vs. 16.9 ± 16.4 minutes day−1; P = 0.02), which contributed to the WLMs expending significantly more calories per week in physical activity compared with the NW group (2,657 ± 1,403 minutes day−1 vs. 2,249 ± 1,125 minutes day−1; P = 0.04). Thus, data using an objective accelerometer measure indicate that WLMs engage in levels of physical activity that are higher than NW individuals and consistent with ACSM recommendations for optimal weight management.
We often are asked how successful WLMs find the time to engage in such high levels of physical activity. Perhaps they limit their "screen time," as one recent report suggests that most NWCR members watch fewer than 10 hours per week of television (in contrast to the average American, who watches approximately 28 hours per week of television) (12). This finding suggests that reducing time spent in sedentary activities may be an important part of successful weight loss maintenance (Table).
In addition to high average levels of physical activity, NWCR members use a variety of dietary strategies to control their weight. Consumption of a low-calorie diet with a relatively low proportion of calories from fat has always been an important characteristic of NWCR members. Participants report consuming about 1,380 ± 573 kcal day−1, with 29.4% ± 11% of calories from fat (11). Men report consuming about 428 kcal day−1 more than women (4). To maintain a diet that is low in calories and fat, NWCR members use food products that have been modified to contain low levels of sugar and fat (9). In fact, WLM use these products more often than individuals who have always been NW. For example, WLMs consume a significantly greater percentage of dairy that is modified (60% vs. 49%) and dressings and sauces that are modified (55% vs. 44%) compared with NWs. Also, WLMs report consuming three times more servings of artificially sweetened soft drinks per day than NWs. Likewise, WLMs consume fewer sweetened beverages than NWs. The use of modified foods may help WLMs consume a satisfying volume of food while not exceeding their calorie and fat goals.
NWCR members tend to eat regularly, with an average of nearly five eating episodes per day. Compared with the average American who may eat as many as 2 to 3 meals per week in fast-food establishments, NWCR members prepare most meals at home, with less than 1 meal per week coming from fast food, on average. The most common dietary strategies for weight maintenance were limiting the intake of certain types of foods such as those high in fat and sugar (92.0%), followed by limiting the quantity of foods eaten (49.2%), limiting the percentage of daily energy from fat (38.1%), counting calories (35.5%), and counting fat grams (30%). In addition, 78% of NWCR members report eating breakfast every day. Last, NWCR members are known for their dietary consistency (2). Participants report eating a diet with relatively little variety and follow the same pattern of eating, with little change for weekends, holidays, or other special occasions (10).
A final behavioral strategy that is often highlighted by the NWCR is self-monitoring (4). As previously mentioned, most NWCR members keep track of calories and/or fat grams. In addition, participants tend to weigh themselves regularly, with 38% weighing daily and 75% weighing at least weekly.
PREDICTORS OF WEIGHT MAINTENANCE
During a 1-year follow-up period, 59% of NWCR members maintain their weight (i.e., regain <5 lbs), 6% lose additional weight, and 35% gain 5 lbs or more (7). A robust pattern of predictors has emerged from several reports that examine weight change prospectively in the NWCR (e.g., 2, 7, 10-12). One of the most important predictors of continued weight maintenance is sustained high levels of physical activity. Notably, participants who experience a simultaneous decline in physical activity and increase in television use appear to be at particularly high risk for weight gain.
Other factors that are reliably associated with weight maintenance include lower caloric intake, a lower percentage of calories from fat and protein, higher levels of dietary restraint (i.e., attention to and control of eating), higher frequency of breakfast eating, a lower frequency of fast-food consumption, and higher levels of dietary consistency. Less depressive symptoms and lower levels of disinhibited eating (less eating in response to internal and external cues such as emotions and the availability of food) also are associated with weight loss maintenance. Thus, successful weight loss maintenance appears to depend on sustaining the healthy lifestyle behaviors for which NWCR members are most known.
CONDENSED VERSION AND BOTTOM LINE
The National Weight Control Registry consists of more than 6,000 individuals who have maintained a weight loss of at least 30 lbs for an average of more than 5 years. These individuals have several behaviors in common, including engaging in high levels of physical activity, consuming a diet low in calories and fat, and self-monitoring of weight and dietary intake. These strategies may be helpful for most Americans who struggle to lose weight and maintain their weight loss.
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