Prevalence of Attempting Weight Loss and Strategies for Controlling Weight

Context Overweight and obesity are increasing in the United States. Changes in diet and physical activity are important for weight control.

Objectives To examine the prevalence of attempting to lose or to maintain weight and to describe weight control strategies among US adults.

Design The Behavioral Risk Factor Surveillance System, a random-digit telephone survey conducted in 1996 by state health departments.

Setting The 49 states (and the District of Columbia) that participated in the survey.

Participants Adults aged 18 years and older (N=107,804).

Main Outcome Measures Reported current weights and goal weights, prevalence of weight loss or maintenance attempts, and strategies used to control weight (eating fewer calories, eating less fat, or using physical activity) by population subgroup.

Results The prevalence of attempting to lose and maintain weight was 28.8% and 35.1% among men and 43.6% and 34.4% among women, respectively. Among those attempting to lose weight, a common strategy was to consume less fat but not fewer calories (34.9% of men and 40.0% of women); only 21.5% of men and 19.4% of women reported using the recommended combination of eating fewer calories and engaging in at least 150 minutes of leisure-time physical activity per week. Among men trying to lose weight, the median weight was 90.4 kg with a goal weight of 81.4 kg. Among women, the median weight was 70.3 kg with a goal weight of 59.0 kg.

Conclusions Weight loss and weight maintenance are common concerns for US men and women. Most persons trying to lose weight are not using the recommended combination of reducing calorie intake and engaging in leisure-time physical activity 150 minutes or more per week.

Weight loss is an important concern for the US population. Consumers spend $33 billion annually for weight loss products and services.¹ Despite these expenditures, overweight and obesity have been increasing in the United States.^2,3 Although long-term weight loss is difficult to achieve, research suggests that changes in both diet and physical activity are important to long-term success.^4-6 For losing weight, both the US Department of Agriculture's Dietary Guidelines and the National Heart, Lung, and Blood Institute's Clinical Guidelines recommend decreasing calorie intake and increasing physical activity.^6,7 Both guidelines recommend at least 30 minutes or more of moderate physical activity on all or most days of the week for all Americans.

We used data from the 1996 state-based Behavioral Risk Factor Surveillance System (BRFSS) to examine the following: (1) the prevalence of trying to lose or maintain weight and factors associated with those attempts, (2) what weight control strategies persons report using in regard to diet and physical activity, and (3) what persons who are trying to control their weight report they weigh and what they would like to weigh.

The BRFSS is a random-digit telephone survey conducted by state health departments. Each state selects an independent probability sample of residents (≥18 years of age) based on random-digit dialing methods. Representative samples from 49 states and the District of Columbia are then pooled.⁸ A detailed description of survey methods is available elsewhere.⁹

Respondents were asked, "Are you now trying to lose weight?" Those who said "no" were asked, "Are you now trying to maintain your weight, that is, to keep from gaining weight?" Only those respondents who answered "yes" to either question were asked the following questions: (1) "Are you trying to eat fewer calories or less fat to lose weight (or keep from gaining weight)?" and (2) "Are you using physical activity or exercise to lose weight (or keep from gaining weight)?" At the end of the interview respondents were asked to report both their height and weight without shoes. Immediately after the question on self-reported weight, respondents were asked about their goal weight: "How much would you like to weigh?" We calculated actual and goal body mass index (BMI) as weight (in kilograms) divided by height (in meters squared) and grouped respondents into the following 3 categories: normal weight, BMI of less than 25.0; overweight, BMI of 25.0 to less than 30.0; and obese, BMI of 30.0 or more.⁶

Participants were asked about the type, duration, and frequency of the 2 leisure-time physical activities they had participated in most frequently during the preceding month. The categories (<150 minutes per week and ≥150 minutes per week) were based on national guidelines of at least 30 minutes or more of physical activity on most or all days of the week.^6,7 Because we did not have information on total minutes of physical activity per day, we defined our categories based on the average weekly physical activity in the last month.

In 1996, 49 states and the District of Columbia participated in the BRFSS and asked all weight control questions (n=118,265). We excluded the following persons from all analyses: women who were pregnant or thought they might be pregnant (n=1756); and persons who did not report sociodemographic or smoking information (n=1585), whether they were trying to lose or maintain weight (n=1644), or their weight, height, or goal weight (n=5476). In our analyses of specific weight control practices, we excluded persons who did not report such practices (n=1334) or leisure-time physical activity (n=1767). The median state cooperation rate (the number of completed interviews divided by the number of completed, refused, and terminated interviews) was 77.9% (range, 54.1%-94.4%).

To identify variables associated with trying to lose or maintain weight, we used separate multiple logistic regressions to estimate the prevalence odds ratios for trying to lose weight vs doing nothing (ie, neither trying to lose nor maintain weight) and for trying to maintain weight vs doing nothing. The independent variables in the model were age, education, race or ethnicity, smoking, and BMI. To account for the complex sampling design and to report weighted findings, SUDAAN was used.¹⁰

About half the respondents were men (49.6%). The majority were white (79.9%); 10.1% were African American and 6.9% were Hispanic. Slightly more than half (53.2%) had at least some college education and about one fifth (23.7%) were 60 years of age and older.

The reported prevalence of trying to lose weight was 28.8% for men and 43.6% for women. Women had a higher prevalence of trying to lose weight than did men within every sociodemographic and weight category (Table 1). Among both sexes, trying to lose weight varied by sociodemographic categories, but was most strongly associated with BMI (Table 2). However, among women, 28.7% of those with normal BMI reported trying to lose weight. Among men, the adjusted odds of trying to lose weight vs doing nothing were similar across most age groups; however, the odds were about 20% higher for those aged 40 to 49 years and 30% lower for those aged 70 years and older compared with those aged 18 to 29 years. Among women, the odds of trying to lose weight decreased with age. Among both sexes, the odds of trying to lose vs doing nothing about weight increased with education and were about 40% lower among current smokers and 30% higher among former smokers than never smokers. The odds of trying to lose weight were lower among blacks than among whites.

Trying to maintain weight was reported by 35.1% of men and 34.4% of women. In contrast to trying to lose weight, the prevalence of trying to maintain weight was inversely associated with BMI category (Table 1). However, among men, the adjusted odds of trying to maintain vs doing nothing about weight were 60% to 70% higher among the overweight and obese subjects than among those with normal weight (Table 2). Among both sexes, the odds of trying to maintain vs doing nothing about weight increased with education and were 30% to 40% lower among current smokers than among never smokers. Among men, the odds of trying to maintain weight vs doing nothing about weight were 20% to 25% higher among those aged 30 to 69 years compared with those aged 18 to 29 years. Among women, the odds of trying to maintain weight decreased after the age of 50 years. The odds of trying to maintain weight were about 20% lower among black women, 10% higher among black men, and 20% higher among Hispanic men than among whites.

Among both sexes trying to lose weight, about 90% reported modifying their diet, a common strategy among all subgroups examined (Table 3). Among both sexes, about half reported consuming fewer calories (with or without less fat); 34.9% of men and 40.0% of women reported consuming less fat only (data not shown). Although two thirds reported using physical activity, only 42.3% of men and 36.8% of women reported engaging in 150 minutes or more of leisure-time physical activity per week (data not shown). Using physical activity as a strategy to lose weight decreased with age and BMI and increased with education level. The combination of any diet modification and exercising 150 minutes or more per week were reported by 36.7% of men and 34.2% of women (data not shown). The combination of eating fewer calories (with or without less fat) and exercising 150 minutes or more per week was reported by 21.5% of men and 19.4% of women.

Among persons trying to maintain weight, about 60% of men and 70% of women reported modifying their diet (Table 3). Among both sexes, slightly more than one fourth reported eating fewer calories (with or without less fat); 31.7% of men and 42.6% of women reported consuming less fat only (data not shown). About half reported using physical activity as a strategy; 46.0% of men and 35.6% of women reported exercising 150 minutes or more per week (data not shown). Using physical activity as a strategy decreased with age and BMI and increased with education. Any diet modification and engaging in 150 minutes or more of leisure-time physical activity per week were reported by 28.6% of men and 26.6% of women (data not shown). Eating fewer calories and exercising 150 minutes or more per week were reported by 13.0% of men and 10.0% of women.

Among men trying to lose, the median reported weight was 90.4 kg and the goal weight was 81.4 kg with a median difference of 8.6 kg (9% of current body weight) (Table 4). Among women, the median current weight was 70.3 kg and the goal weight was 59.0 kg, with a median difference of 8.9 kg (13% of current body weight).

Among persons trying to lose weight, both the median current BMI and goal BMI were higher for men than for women. More than half of men trying to lose were currently overweight, and one third were obese. Among women trying to lose, slightly more than one third were currently normal weight, slightly more than one third were overweight, and about one fourth were obese. Among men, 37% had a goal BMI in the normal weight range compared with 82% among women. Among persons trying to maintain weight, the median current weight was 80.6 kg for men and 61.0 kg for women. The median difference between current weight and goal weight was 0 kg for men and 1.8 kg for women (3% of current body weight). Among those trying to maintain weight, both the median current BMI and goal BMI were higher for men than women. Among men, 52% had a goal weight in the normal weight category, whereas 87% of women did so.

Our survey showed that more than two thirds of US adults are trying to lose or maintain weight. Only a fifth of those trying to lose weight reported using a combination of eating fewer calories and engaging in 150 minutes or more of leisure-time physical activity each week. Thus, although most Americans reported using diet, physical activity, or both for weight loss, only a minority were using the recommended combination.^6,7 Whether this disparity reflects a lack of knowledge about weight control methods or an inability to implement these methods effectively, or both, cannot be answered with the BRFSS study.

The prevalence of attempted weight loss in the 1996 BRFSS—29% among men and 44% among women—is somewhat higher than that previously reported. Both the 1989 BRFSS and 1990 National Health Interview Survey found that 23% of men and 40% of women reported trying to lose weight.^11,12 This increase may reflect the secular increase in obesity in the population.^2,3 The National Health Interview Survey found that among those trying to lose weight, 76% of men and 82% of women reported they were "eating less," and about 60% of both sexes reported increasing physical activity. In the Weight Loss Practices Survey, a nationally representative survey of persons trying to lose weight, 81% of men and 87% of women reported "eating differently," and 78% of men and 83% of women reported using exercise.¹³ Thus, these national surveys generally support our findings that most persons try to lose weight by eating less and exercising more.

We found strong sex differences in the prevalence of trying to lose weight; however, we did not find differences in weight loss strategies. Women report trying to lose weight at a lower BMI than men; in fact, about 30% of normal weight women reported trying to lose weight. The distribution of trying to lose weight seemed to move up a level in women with 60% of overweight women trying to lose, whereas this level was reached only in obese men. Among those trying to lose weight, women were about 2 times more likely than men to report a goal weight in the normal range. We speculate that this greater concern among women may reflect increased societal pressure toward thinness. Despite these sex differences, men and women were equally likely to report eating fewer calories and exercising 150 or more minutes per week. Because women, especially overweight women, are more likely than men to underreport their weight, at least some of the differences in sex-specific patterns of attempted weight loss by BMI may be explained by differential misclassification of BMI.¹⁴

Among persons trying to lose weight, eating less fat was a common strategy; however, reduction of fat intake is not an effective strategy unless calories are also reduced.⁶ It is unclear whether reducing fat without intentional reduction in calories will, in most cases, ultimately lead to reduced caloric intake. Allred¹⁵ has hypothesized that an overemphasis on consumption of low-fat foods may have contributed to an increase in total energy intake in the United States. Weight-conscious persons may restrict calories from high-fat foods only to eat as many or more calories from lower-fat foods.^16,17

Regular physical activity is a key factor in successful weight loss and long-term weight maintenance.^4,18,19 In our study, two thirds of persons reported using physical activity as a means of weight loss; however, only 40% reported exercising 150 minutes or more per week, the minimal level of physical activity recommended in national guidelines for all Americans.^6,7 Of particular concern was the finding that using physical activity as a method to lose weight was least common among the obese, the least educated, and the oldest. This suggests a need for better communication by health care professionals to facilitate the adoption of physical activity for weight control, especially among these groups. A study of overweight women shows that prescribing multiple short bouts of exercise may improve adherence better than 1 continuous bout.²⁰

This study has several limitations. Although the data include representative samples from 49 states and the District of Columbia, nonetheless, the BRFSS was designed to provide state level estimates. Because respondents tend to underreport weight,¹⁴ the prevalence of overweight is likely underestimated. Estimates of physical activity are also likely to be underestimated because respondents were allowed to report only 2 structured leisure-time activities. However, BRFSS estimates of structured leisure-time physical activity are comparable to those in a national survey based on 20 reported activities.²¹ Unstructured activities, such as housework or on-the-job activities, were not assessed. Because the survey did not include an in-depth dietary assessment, calorie and fat reduction could not be quantified. The overall median state nonresponse of 22.1% and item nonresponse of 7.7% for the questions on current and goal weight are of concern because the heaviest persons may be more likely to refuse.

Even though weight control is a commonly reported behavior, obesity is increasing in the United States.^2,3 This increase is most likely due to a secular increase in energy intake combined with a decline in physical activity brought about by environmental and societal changes (such as through the use of automobiles, labor-saving devices, and television/video entertainment) and through the food supply (such as the ready availability of "fast foods").^3,22 Thus, reversing the trend in obesity will require change at the societal and environmental as well as at the individual level. At the individual level, there is a need for health care professionals to develop expertise in counseling patients to prevent weight gain or to lose weight through lower total caloric consumption and increased physical activity.