Introduction

Obesity, defined as BMI 30 kg/m², is a major public health threat among many American adults today. According to the Chartbook on Trends in the Health of Americans (1), 65% of adults were reported to be overweight, and 31% were reported to be obese in 1999 to 2000. Obesity may be prevented and treated, and weight loss can be maintained with various dietary modifications. Specifically, weight maintenance by means of qualitative dietary changes (reducing total dietary fat and saturated fat; increasing dietary fiber, fruits, and vegetables) may be more successful, once learned, compared with maintenance with only reduced calorie intake (2). Despite potentially successful strategies for long-term weight loss maintenance, there are limited long-term evaluations of weight loss programs in academic or commercial settings, and weight is often regained after initial weight loss. One review found that only 13% to 22% of persons who initially lost 5 kg or more maintained 100% of their weight loss 5 years post-treatment (3).

An academic health center-based weight control program that has reported long-term weight loss results is the University of Alabama at Birmingham (UAB)¹ EatRight Weight Management Program. Long-term weight maintenance (maintaining all weight lost), after an average of 25 months, was achieved in 53% of these patients, and only 23% regained all of their lost weight (4). The physician-directed EatRight Weight Management Program is a 12-week program taught by registered dietitians that encourages weight loss/maintenance through qualitative dietary changes. The EatRight program is based on the concept of time-calorie displacement, which encourages a substantial intake of foods that have a low energy density (fruits, vegetables, whole grains) and limited consumption of high-energy density foods (meats, cheeses, sugars, and fats). The EatRight dietary pattern prolongs eating time, displaces intake of more energy-dense foods, and induces satiety at one-half the energy consumption when compared with a high-energy density diet (5, 6). The EatRight program also incorporates behavioral intervention, including a focus on social and cognitive factors that reduce or remove barriers to lifestyle change and achievement of goals.

Before 1996, the dietary principles of EatRight were delivered primarily in an individual setting over the course of an average of 15 weeks, or more if indicated. The contemporary program uses a group-based model in the 12-week format, with a standardized curriculum led by a registered dietitian. Given substantial changes in the food environment, increasing prevalence of obesity, and dietary intake trends, we wanted to determine whether the dietary pattern provided in the EatRight program was associated with long-term weight maintenance in a contemporary cohort. Our observational study was primarily designed to determine weight outcomes for a sample of participants at least 1 year after completing UAB's EatRight Weight Management Program. The secondary aim was to determine dietary intake patterns that are associated with various patterns of weight change after participation.

Research Methods and Procedures

Participants

Study participants were recruited from the UAB EatRight Weight Management Program database. Participants were defined as those who attended three or more classes. They were contacted by a phone call, e-mail, or letter mailed to their home address if they had participated in years 2001 to 2003 and had not participated in the program again since that time. Our goal was to make contact with 50% of former EatRight participants who could be eligible for participation. We attempted to contact 194 of the 425 participants who met the participation criteria. Of the 194 persons we attempted to contact, 23 persons could not be reached, due to an incorrect phone number or address. The only exclusion criterion was the self-report of any ongoing condition/illness that may have contributed to or caused significant weight gain/loss (e.g., pregnancy, cancer). Of the 171 persons contacted, 5 were excluded as a result of this criterion. Potential participants were told that the EatRight program was conducting follow-up measurements of former participants to complete a program evaluation. All potential participants were offered a $25 travel reimbursement and a choice of an additional incentive valued at $25 (discounts to local businesses or a cookbook). There were 74 persons who agreed to participate in the follow-up study (45% participation rate). In the previous report of long-term weight outcomes for EatRight participants, the participation rate was 40% . Participants came for a follow-up visit between June 2004 and January 2005. This study was approved by the UAB Institutional Review Board, and written informed consent was obtained from each participant.

Assessment of Body Weight

Body weight was measured in light clothing without shoes by a Tanita digital scale (Model BWB500A; Tanita, Tokyo, Japan). Height was measured using a wall-mounted stadiometer. BMI was calculated as weight (kilograms)/height (meters)².

Assessment of Dietary Intake

Dietary intake was estimated from a 4-day food record that included 2 weekdays and 2 weekend days. The participants completed the food records before coming in for their follow-up visit. Seventy-one of the 74 participants returned their food records, and the dietary analysis is limited to this subset. Food records were analyzed using the University of Minnesota Nutrition Data System for Research (version 5.0). The percentage of recommended Food and Drug Administration (FDA) serving size consumed by former EatRight participants was determined by the following calculation: amount of food (g)/FDA serving size (g). The recommended FDA serving size was calculated for the following food groups: meat/dairy, fats and nuts, fruits, vegetables, grains, and caloric beverages excluding milk. Energy density was determined using the methodology proposed by Ledikwe et al. (7) which entails calculating energy density from food only as energy (kcal)/weight of food (g). Beverages, including milk, alcohol, other caloric drinks, and non-caloric drinks, were removed from the dataset using the following food group identification numbers to identify them in the Nutrition Data System for Research: 24, 31, 35, 62, 116, 117, 118, 119, 120, 121, and 122.

Statistical Analysis

Descriptive statistics were calculated for all study participants using the SPSS/PC statistical program (version 13.0 for Windows; SPSS, Inc., Chicago, IL). Weight maintenance (maintainers) was defined as gaining <5% of body weight since completion of the EatRight program and staying below the initial weight at the time of entry into the program. Those who gained 5% or more of their body weight since completion were classified as gainers. Using these definitions to categorize follow-up participants, we compared dietary intake patterns, including unadjusted means for calories, fiber, and percentage of calories from fat, carbohydrate, protein, and saturated fat between maintainers and gainers using Student's t tests. Correlations between weight status and dietary intakes were obtained using Spearman correlations. Adjusted means were compared using general linear modeling with covariates of age, gender, weight at completion of EatRight, and length of follow-up.

Results

The majority of participants (81% ; n = 74) were white, and the average age was 50 years. Participants started the EatRight Weight Management Program with an average BMI of 33.7 kg/m². During EatRight, participants lost an average of 4.0 kg, making the mean BMI after participation 32.3 kg/m². The former EatRight participants who were contacted but declined to participate in the follow-up assessment or were ineligible (n = 97) had the same mean age and a slightly higher, but not significantly different, BMI of 35.7 kg/m² compared with those who agreed to participate. Non-participants also had similar weight loss during EatRight as those who participated. Those who declined to participate usually cited inconvenience as a primary factor. After a mean follow-up time of 2.2 years, the average weight change was an increase of 0.59 kg (mean BMI, 32.5 kg/m²). The distribution of change in weight over time did not show a trend toward significant weight regain for the population. The mean daily dietary intake of the 71 participants with complete food records was 1695 calories, with 36% calories from fat, 48% from carbohydrate, and 16% from protein.

Of the 74 participants, 78.4% (n = 59) were maintainers, and 21.6% (n = 15) were gainers at follow-up. The characteristics of the maintainers and gainers are shown in Table 1. In general, those who maintained weight loss weighed less at the start of the EatRight program and were slightly older at the time of follow-up. Weight loss during the program was 1.14 kg greater for gainers than maintainers. The mean follow-up time was 6 months greater for the gainers, and during the 2.5 years since completing the program, weight change in this group averaged an increase of more than 7.9 kg. However, during the 2-year follow-up period for the maintainers, weight change averaged a decrease of 1.3 kg. In the maintainers group, 34 participants (45.9% of the total cohort) lost additional weight after completing the EatRight program.

Table 1. - Characteristics of subjects (n = 74).

Full table

Characteristics and correlations of the daily dietary intakes of maintainers and gainers are shown in Table 2. On average, the entire group of former EatRight participants had a moderate- to high-fat diet, with 11% of calories from saturated fat sources. Fiber intake was below the recommended daily intake of 14 g/1000 kcal (8), and the ratio of polyunsaturated-to-saturated fat (P-to-S ratio) was at the lower limit of ratios that have been shown to have a beneficial effect on cardiovascular risk factors (9, 10, 11). Compared with those who gained weight, maintainers' unadjusted intakes were significantly lower in total calories, energy density, and percentage of calories from fat and saturated fat. After adjustment for age, gender, body weight at the completion of the EatRight program, and length of follow-up time, only energy density remained significantly lower in maintainers, while total calories, saturated fat calories, and P-to-S ratio showed a trend toward a significant difference. A lower intake of total calories, energy density, and calories from fat and saturated fat was significantly correlated with maintaining weight loss, as was a higher intake of calories from carbohydrates and a higher P-to-S ratio. Mean food weight was similar for those who gained weight and those who maintained body weight.

Table 2. - Characteristics of the dietary patterns of maintainers and gainers.

Full table

The maintainers group included 34 participants who lost weight during the follow-up time period. When compared with others in the maintainer group (n = 25), those who lost weight during follow-up had similar dietary intake patterns as maintainers. There were no statistical differences in total energy, percentage of calories from any macronutrients, fiber, energy density, or mean food weight.

Percentages of recommended FDA serving sizes consumed by maintainers and gainers are shown in Table 3. On average, those who gained 5% or more of their body weight during follow-up had larger portions of food items from several food groups including meat/dairy, fats/nuts, fruits, and beverages. Maintainers had slightly greater serving sizes of vegetables and slightly smaller serving sizes of grains than gainers, but these differences were not significant.

Table 3. - Mean percentage of recommended FDA serving size consumed by former EatRight participants^*.

Full table

Discussion

In our observational study of a volunteer sample, we found that during a follow-up period of 2 years, 78% of participants gained <5% of their weight after participation in the EatRight Weight Management Program, and 46% gained no weight or lost additional weight. These results represent a best-case scenario because a substantial proportion of the people contacted to participate declined. If we assume that all declining participants gained 5% of their body weight, it would mean that ultimately 31.2% of the study sample maintained their body weight. Results from this contemporary analysis are consistent with results reported in 1991 by Fitzwater et al. (4) when the EatRight principles were delivered primarily in an individual setting. More importantly, our findings add significant information about dietary patterns associated with weight maintenance after participation in EatRight. Participants who were maintainers, including those who lost additional weight, showed a trend toward eating fewer calories, consumed similar volumes of food, and had a significantly lower energy-density intake compared with those who gained weight; maintainers also limited portion sizes of key food groups that can be high in energy density.

The overall mean weight change of all volunteers in this study was a gain of 0.59 kg. Few behavioral, non-meal replacement weight loss programs, if any, have reported successful long-term weight maintenance to this degree. The major challenge Americans face is not how to lose weight, but how to keep it off. Results from the National Weight Control Registry of successful weight losers suggest that weight loss methods vary widely, but maintaining body weight after weight loss requires a fairly common set of behaviors such as consuming a low-fat diet, high levels of physical activity, eating breakfast everyday, and using self-monitoring (12). We believe that the EatRight principles shown to be associated with successful weight maintenance in this cohort could be beneficial for the general population.

Maintainers in our population had dietary patterns that were consistent with the EatRight principles, consuming a low-energy-density dietary pattern. There were few statistically significant differences in macronutrient intake after adjustment for several key covariates; however, it is likely that the combination of key factors that affect dietary energy density played an important role in the observed difference in energy density between the groups. Key factors such as slightly lower total calories, calories from fat and saturated fat, and slightly higher fiber and carbohydrate intake each contribute to energy density, resulting in a modest but significant positive correlation with body weight maintenance and continued weight loss. This observational study demonstrates that dramatic differences in macronutrient intake or large volumes of food are unlikely to be the key factors differentiating those who gain significant amounts of weight over time compared with those who maintain body weight. Small energy differences, which may be less than the 244 kcal we observed, for the same volume of food could easily account for differential weight gain over time.

Some researchers have shown that a lower carbohydrate intake results in greater weight loss than a low-fat, high-carbohydrate diet (13, 14). However, a low-carbohydrate intake has not been shown to produce greater weight maintenance at 1 year of follow-up (14). In our population, maintainers consumed a diet that was 50% carbohydrate. According to Ma et al. (15), a higher dietary glycemic index was associated with a higher BMI, but the percentage of calories from carbohydrate and total carbohydrate intake was not associated with BMI. These results and our own may indicate that the type of carbohydrate, and not the amount alone, may be more related to body weight and weight maintenance. Indeed, in our study, carbohydrate intake was inversely associated with potential for weight gain during follow-up. Given the lower energy-density pattern of maintainers, one could speculate that this inverse relationship is driven partially by carbohydrate food sources that are high in fiber and water content, increasing food volume without significantly increasing calorie content.

In a previous review to find the characteristics of successful weight maintainers (16), it was found that weight maintenance was associated with lower energy intake, less dietary fat, and reduced portion sizes. Servings sizes have increased inside and outside the home (17), which may be hindering the weight maintenance efforts of the U.S. population. We found that the serving sizes of meats/dairy, fats, fruits, and beverages were significantly higher for gainers than maintainers. Results from controlled studies have shown that portion sizes significantly influence energy intake. Rolls et al. (18) found that subjects consumed 30% more energy when offered larger vs. smaller portions of the same foods. Further evaluation is needed to determine the role that portion sizes play in the maintenance of body weight.

Our observational study was limited by the fact that participation was voluntary; some participants who gained weight may have been lost to follow-up or unwilling to return for follow-up measurements. Future assessments of EatRight long-term weight loss maintenance will need to include higher levels of data collection from all participants. Also, self-report of dietary intake may have missed some food items or inaccurately estimated amounts consumed. However, specific instructions on completion of the food records were provided to all participants; in addition, the methods used by participants to collect the food records were similar to those used during the EatRight program for self-monitoring, making the procedures generally familiar to everyone. Our definitions of gainers and maintainers were limited to some degree, such that a person classified as a gainer may have, indeed, been below his/her starting weight. Likewise, maintainers included those who continued to lose weight after participation. However, our definitions did allow for a basic categorization of the participants' weight trajectories since completion of the program. Finally, our limited sample size reduced our ability to detect statistically significant differences in several nutrient categories after adjustment for key covariates.

These data suggest that this cohort has achieved long-term weight maintenance because they have adopted some of the EatRight principles into their everyday lifestyles. They consume low-energy density, lower fat foods and choose smaller portion sizes of energy-dense foods. This study provides new and important details about the dietary patterns associated with body weight maintenance. Low-energy density food consumption, particularly unlimited intake of fruits and vegetables, is a cornerstone of the EatRight program. It appears that this approach may be a valuable method for promoting long-term success with weight control. Further analyses are needed to understand the impact of other lifestyle factors such as physical activity on long-term weight maintenance when combined with this type of dietary pattern.

Notes

¹ Nonstandard abbreviations: UAB, University of Alabama at Birmingham; FDA, Food and Drug Administration; P-to-S ratio, ratio of polyunsaturated-to-saturated fat.

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Acknowledgments

This study was supported, in part, by UAB's Clinical Nutrition Research Center, and from the National Institute of Diabetes and Digestive and Kidney Diseases Grant 5 P30 DK56336.