The main finding of this study was that primary care providers, in collaboration with auxiliary healthcare professionals, successfully delivered a behavioral lifestyle intervention in a primary care setting, which resulted in significant weight loss, improved eating behaviors, and increased physical activity. Obese patients in the Brief LC and Enhanced Brief LC groups lost 2.9 and 4.6 kg, respectively, at month 24, compared to 1.7 kg in Usual Care. The addition of meal replacements or weight loss medication to lifestyle coaching significantly increased the mean weight loss in the Enhanced group by 2.9 kg, compared with Usual Care.
Participants in the Enhanced Brief LC group also reported greater improvements in dietary restraint and physical activity at month 24 than those in Usual Care. Although individuals in the Brief LC group also reported more favorable long-term improvements in these variables than Usual Care participants, these changes were not sufficient to translate into significantly greater weight loss at 24 months. None of the three groups reported substantial changes in hunger, which was surprising for the Enhanced Brief LC group, given some participants’ use of the weight loss medication sibutramine.
There were no significant differences among the three groups at months 6 or 24 in changes in fruit and vegetable intake or in the percentage of calories consumed from fat. However, the lack of change may have been attributable to our participants’ high reported baseline consumption of fruits and vegetables (~5.8 servings), relative to the average daily servings consumed by U. S. adults (~2.7 servings).22
Likewise, our participants’ reported baseline estimates of percent energy intake from fat (32.9%) were within the 20–35% of calories range recommended by the Dietary Guidelines for Americans.23
Our participants may well have overestimated their initial fruit and vegetable intake, thus, attenuating estimates of change at months 6 and 24.
The present results add to prior efforts to identify predictors or correlates of weight loss. The baseline values of selected measures, such as cognitive restraint, disinhibition and hunger, were not successful in predicting weight loss and indicate that clinicians should not use these or similar measures to screen patients for weight loss. By contrast, the change in cognitive restraint from baseline to month 6 correlated with weight loss at this time, indicating (as expected) that as participants increased efforts to restrict their food intake, they lost more weight. Change in hunger also contributed modestly to weight loss at this time, as did participants attendance of PCP visits. Greater attendance was associated with greater weight loss, although these variables were only weakly related in the stepwise, multivariable model.
When examining the two lifestyle interventions together (excluding Usual Care), participants’ completion of their food records during the first 6 months proved to be by far the strongest correlate of weight loss during this time, accounting for 33.4% of the variance. The greater the percentage of records participants completed, the more weight they lost, as demonstrated in several prior studies,24–27
and as summarized in a recent systematic review by Burke et al
Moreover, completion of food records during the first 6 months was the strongest predictor of weight change at month 24, explaining 19.3% of the variance in this variable. Milsom et al.
similarly reported that increased frequency of record keeping (7.1 versus 2.7 days per month) during the first 6 months was associated with greater weight loss maintenance at 3.5 years.29
Collectively, these findings underscore the importance of ensuring the participants record their food intake regularly during the initial months of a behavioral weight loss program. Participants who only marginally complete – or do not complete – diaries during the first 2 weeks should receive additional counseling to help them master this behavior, given its strong relationship to short- and long-term weight loss.
Early weight loss is also a known predictor of subsequent weight loss.30–32
In the current analysis, participants who achieved a 5% weight loss at 6 months had 4.7 times greater odds of maintaining a 5% weight loss at 24 months. These findings replicate prior studies which found initial weight loss was a predictor of better weight loss maintenance.33,34
Strengths of this study include the successful provision of treatment by primary care providers and auxiliary health professionals within their own practice sites (as opposed to interventions delivered by highly specialized personnel at academic-based institutions). This has significant implications for the delivery of behavioral interventions in primary care settings. Second, the study population was diverse and included patients at both urban and suburban practice sites, which further extends our findings to the general primary care population. Third, outcome measures were collected by trained and certified staff members using calibrated equipment, standardized procedures, and validated questionnaires.
The study also had several limitations. Numerous factors that influence eating and activity behaviors, as well as weight loss (e.g., treatment acceptability, motivation to change) were not examined in this study. In addition, the measurement of usual dietary intake or physical activity often relies on self-reported instruments, which may be cognitively difficult for respondents and are vulnerable to measurement error (depending on the time period considered, the ease of the instrument, and the characteristics of the respondents).
Findings from our study and others3,4
have important clinical implications, as several organizations have recently endorsed the use of lifestyle counseling in routine clinical practice. In November 2011, the Center for Medicare and Medicare services announced that it will cover intensive behavioral interventions delivered in primary care practice to obese Medicare beneficiaries.35
This includes weekly face-to-face visits with the primary care provider for the first month, followed by bi-monthly face-to-face visits for months 2–6, and then monthly visits for months 7–12 (provided the patient loses ≥ 3 kg in the first 6 months). Additionally, the U.S. Preventive Services Task Force recently published new clinical guidelines recommending that clinicians screen adults for obesity and offer or refer patients with a body mass index ≥ 30 kg/m2
to intensive, multicomponent behavioral interventions (Grade B recommendation).36
Results of our study indicate that a primary care-based lifestyle intervention delivered by primary care providers, with the assistance of auxiliary health care workers, can result in clinically meaningful weight loss in some patients, with corresponding improvements in eating restraint and energy expenditure. Moreover, treatment adherence and weight loss at month 6 were strong predictors of long-term weight loss (24 months). These findings offer PCPs new methods to assist their obese patients with weight management.