Weight loss maintenance in successful weight losers: surgical versus non-surgical methods

Introduction

For the approximately 1 in 20 individuals who are severely obese (BMI ≥ 40 kg/m² or > 100 pounds overweight)¹, bariatric surgery is considered the most effective method for producing long-term weight loss.^2,3 On average, individuals who have bariatric surgery lose about 25% of their initial body weight within the first 12 months postoperatively.^4,5 Comparatively, individuals in behavioral weight loss treatments typically lose 10% of their body weight.^6,7 However, in two recent studies using more intensive behavioral treatments in severely obese individuals, weight losses averaged 25% among treatment completers and 18% of participants lost 100 pounds or more.^8,9

While surgical procedures more reliably produce large initial weight losses, it is not clear whether surgical patients are more successful at maintaining their weight losses than individuals who have lost comparable amounts of weight through non-surgical means. In the Swedish Obese Subjects (SOS) intervention study, a large prospective study of the effects of weight loss in severely obese patients, surgically-treated subjects regained nearly a third of the weight that they lost by 6-year follow-up.⁵ In the two behavioral studies cited above, patients who achieved large initial weight losses of ≥ 100 lbs went on to regain between 35% and 38% of the weight they initially lost over the next 2 years and nearly 50% of this amount by 5 years.^8,9 To date, there has not been a direct comparison of weight loss maintenance in individuals who have achieved significant weight loss through bariatric surgery or non-surgical approaches.

The National Weight Control Registry (NWCR), an ongoing longitudinal study of successful weight loss maintainers, provides a unique resource for comparing individuals who have lost large amounts of weight through surgical or non-surgical means. Previously, NWCR members who lost weight through bariatric surgery were compared with members who lost comparable amounts of weight through non-surgical methods, although these groups were not compared prospectively on weight loss maintenance.¹⁰

The primary objective of the current study was to evaluate whether NWCR participants who had lost and maintained comparable large amounts of weight through either bariatric surgery or non-surgical methods differed in weight regain over time. In addition, we compared the groups on weight maintenance behaviors and psychological characteristics at registry entry and 1 year. Finally, we evaluated whether the contribution of behaviors and psychological characteristics to 1 year weight regain was a function of weight loss method.

Materials and Methods

Statement of Ethics

We certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research. This study was approved by The Miriam Hospital Institutional Review Board, Providence, RI.

Results

Discussion

Although achievement of large initial weight losses occurs more frequently and rapidly through bariatric surgery than through non-surgical or behavioral approaches, it is not known whether those who do succeed through behavioral approaches are more or less successful at long-term maintenance of their weight loss. The NWCR provides a unique opportunity to make this comparison. Using the NWCR, we were able to identify matched groups of surgical and non-surgical patients who had on average lost 56 kg or over forty percent (41%) of their maximum body weight, had changed from severely obese (BMI = 47.4 kg/m²) to overweight (BMI = 27.9 kg/m²), and had maintained the large weight losses for an average of 5.5 years at entry into the study.

There were no significant differences in the amount of weight regain between surgical and non-surgical participants. For both groups, weight regain averaged about 2 kg per year. Moreover, the majority of surgical and non-surgical participants remained within ± 4.9 kg of their baseline weight at years 1 and 2. These findings suggest that individuals who have lost and maintained large amounts of weight through non-surgical approaches may be equally successful at maintaining their weight losses as individuals who have lost comparable amounts of weight through surgical approaches.

Similar to our previous work,¹⁰ surgical and non-surgical participants were clearly differentiated by the behaviors they used to maintain their weight loss at entry into the study, and the current study showed that these differences persisted over time. These behavioral differences suggest that the participants who achieved large weight losses through non-surgical methods had to work harder to maintain their weight losses than the surgical participants. Findings indicated that while both groups reported a similar caloric intake, non-surgical participants reported more conscious control over their eating and a lower percentage of calories from fat at both time points. Surgical participants reported consuming a high-fat diet (≥ 35% of kcal from fat), whereas non-surgical participants consumed a low-fat diet (< 28% of kcal from fat).²⁷ Similarly, surgical participants reported more frequent consumption of fast food meals. The surgical group's higher-fat diet may have been a function of time since surgery. With increasing duration of the postoperative period and stretching of the gastric pouch and stoma, not only could higher fat foods be better digested but also greater amounts could be consumed, thereby promoting greater fat intake.²⁸ Surgical participants also derived a lesser percentage of calories from carbohydrates, possibly owing to learned dumping-related aversions to high sugar foods, modified taste perceptions and/or macronutrient balance such that as fat calories increased, carbohydrates calories decreased.^29-31

Whether the non-surgical participants' lower fat/higher carbohydrate diet is healthier or provides additional weight control benefits compared to the surgical participants' higher fat/lower carbohydrate diet is uncertain. In a recent randomized controlled trial involving obese patients, Shai et al.,³² showed that a low-fat, restricted calorie diet produced significantly less weight loss and lesser reduction in total cholesterol to HDL ratio over 2 yrs compared with a low-carbohydrate, non-restricted calorie diet. By contrast, other research has shown no significant differences in long-term weight control in participants consuming a low fat vs. low carbohydrate diet).^31,33 The effects of different diets on long-term weight loss and disease risk profiles in individuals who have lost large amounts of weight through surgical and non-surgical approaches requires further investigation.

Consistent with previous studies of successful weight maintainers, both groups reported engaging in high levels of physical activity.^17,34 Non-surgical participants, similar to our previous study¹⁰, reported expending significantly more calories through physical activity than surgical participants. In addition, only one-third of the surgical group reported engaging in a level of physical activity consistent with recommendations for prevention of weight regain compared with 60% of the non-surgical group.²⁶ Although surgical participants achieved similar weight maintenance with less physical activity, the long-term consequences of these lower and declining levels of physical activity over time are unknown. Longitudinal research demonstrates that rate of recovery from comorbidities after bariatric surgery decelerates along with weight regain.⁴ Given the role of physical activity in non-surgical weight maintenance and health-related outcomes independent of body weight, the role of physical activity in promoting weight loss maintenance in bariatric surgery patients merits investigation in treatment-controlled trials.^35,36

Interestingly, despite both groups reporting high levels of activity-related energy expenditure and low calorie intake, weight regain still occurred. One explanation for this finding may be measurement error associated with use of self-report instruments; participants may have overestimated their physical activity and underestimated their caloric intake.^37,38 The occurrence of weight regain may also be attributed to homeostatic processes that oppose long-term weight loss in post-obese individuals.^39-42

Examination of psychological characteristics in the surgery and non-surgical participants revealed that both groups reported an increase in depressive symptoms from study entry to 1 year follow-up. However, whether these increased levels of depressive symptoms still remain significantly below pre-weight loss levels cannot be determined since depressive symptoms were only assessed after weight loss. Previous studies involving assessment of depression before and after successful surgical and non-surgical weight loss treatments indicate improvements, not worsening, in depression^{7, 43-46}

Interestingly, surgery participants were found to report higher levels of depression than non-surgical participants at both study entry and follow-up. This finding should be interpreted with caution because participants were not randomized to surgery and non-surgical groups and, as noted above, pre-weight loss levels of depressive symptoms are unknown. Nonetheless, it is still concerning that 44% of surgical participants reported depressive symptoms that surpassed the minimal threshold for clinical significance, particularly in light of recent findings indicating a higher risk of suicide death in bariatric surgery patients.^47,48 Given the estimated 25% to 30% of patients who report symptoms indicative of clinical depression at the time of evaluation for bariatric surgery⁴⁹, further study and monitoring of the course of depressive symptoms and related factors including stress across longer postoperative periods is needed.

We also evaluated the importance of behaviors and psychological characteristics at study entry and across 1 year in relation to weight regain within both groups. Interestingly, our findings showed that initial method of weight loss did not moderate associations between behaviors or psychological characteristics and weight regain. Higher levels of disinhibition at study entry and increases in disinhibition over 1 year emerged as the only significant predictors of weight regain in surgical and non-surgical participants. These findings are consistent with other studies showing that increased susceptibility to cues that trigger impulsive eating undermines weight loss and long-term weight loss maintenance.^17,50 Recent research also shows that grazing and loss of control over eating in bariatric surgery patients is related to poorer weight loss outcomes.⁵¹ Our findings that disinhibition is associated with weight regain beyond the active weight loss period suggests that modifying disinhibited eating patterns might improve weight loss maintenance following bariatric surgery.

This study has several limitations. Participants in this study were derived from the NWCR, a self-selected sample of successful weight loss maintainers who may be more determined in their weight loss efforts than the general population of successful weight loss maintainers, and are certainly different from the general population of obese persons. The gender and ethnic composition of participants in this study, while being less diverse than that of the general population of overweight individuals, resembles national trends in individuals who undergo bariatric surgery.^52,53 Further, the surgical group may have achieved the significant weight losses more easily and at a faster rate than those who achieved these weight losses non-surgically. Although not representative of the population at large, these NWCR participants provided an opportunity to compare those who were successful at maintaining large weight losses via bariatric surgery or non-surgical methods and to see if they differed in long-term maintenance and associated behaviors and psychological characteristics over time.

Another limitation is the use of self-report data. In a previous NWCR study, participants' self-reported weights were shown to strongly correlate with those from physician records.¹⁷ Nevertheless, self-reporting of weight and weight-related behaviors is still subject to issues of underreporting/overreporting and social desirability.^37,38 Our sample size may also have limited the ability to detect small effects. Finally, although we controlled for group differences in educational at study entry, education does not necessarily encompass all SES-related factors such as type of employment, location of residence/neighborhood and income level that could affect both performance of various weight control behaviors and access to related literature and information. Strengths of this study include the prospective design and the matching of surgical and non-surgical participants on demographic and multiple weight characteristics and assessment of a wide range of behaviors and psychological characteristics.

In summary, this study suggests that weight loss and maintenance comparable to that observed after bariatric surgery can be accomplished through behavioral methods alone, although this may involve more intensive efforts over a longer duration. Future research should focus on ways to increase and maintain physical activity and better monitor psychological parameters in bariatric surgery patients to facilitate optimal long-term weight control. In addition, designing methods to increases resistance to cues that trigger overeating among individuals who have achieved large weight losses through bariatric or non-surgical methods may assist in preventing weight regain.