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Weight loss response to sleeve gastrectomy varies, but predicting its effectiveness remains elusive. A small prospective study in examined the attributes associated with control of eating (CoE) in the early postoperative period to predict a good versus poor response 1 year later.

Administering the 21-item Control of Eating Questionnaire before and at 3-, 6-, and 12-months after the surgery, Eduardo Grunvald, MD, of the University of California San Diego, and colleagues studied 41 patients (85% of whom were women) with a median baseline body mass index of 43.6. The questionnaire is a multidimensional measure of appetite, satiety, cravings, and mood regulation.

The primary outcomes were changes in CoE attributes and percentage of total weight loss (%TWL) 12 months post-surgery. Participants were categorized based on %TWL as good responders (≥25%) or poor responders (<25%). At 3 months, question 19 – "Generally, how difficult has it been to control your eating?" corresponding to the "Difficulty to control eating" CoE attribute – seemed to best predict weight loss at 1 year and distinguish between good and poor responders, the researchers said.

A "difficulty to control eating score" of ≤7 at 3 months was a strong and independent predictor of reaching a successful weight loss target of at least 25% TWL at 1 year.

Grunvald, medical director of the Weight Management Program, elaborated on the results in the following interview.

What was the contextual background for this study?

Grunvald: Contrary to previous mechanistic considerations that see surgical weight loss driven by making the stomach smaller or by calorie malabsorption, metabolic bariatric surgery (MBS) is thought to be highly effective owing to neurohormonal changes and other physiologic modifications that alter central nervous system signaling for regulating weight. The exact mechanisms are not well understood.

There's a great deal of individual variability regarding response to bariatric procedures. Anecdotally, patients express changes in satiety, satiation, and hedonic ingestive behaviors after MBS. We wanted to correlate these responses to post-surgical weight loss outcomes 1 year after MBS -- specifically sleeve gastrectomy. We chose the CoEQ because the specific questions in this visual analogue scale closely reflect questions we ask patients in the clinic.

To our knowledge, this study is the first to use this survey in bariatric surgery patients to examine this question.

Did you start with a working hypothesis and was it borne out?

Grunvald: Yes, our hypothesis was that stronger weight loss outcomes would correlate with sustained changes in CoE attributes. We were really excited to see that this study, with a relatively small number of participants, was able to demonstrate that by utilizing the CoEQ early after the surgery we may predict how successful our patients are in losing weight 1 year after the surgical intervention.

Do your results align with any other research in this field?

Grunvald: Yes, there are multiple studies that examine post-surgical weight loss and various questionnaires addressing hunger and cravings, as well as changes in eating behaviors. Most are small studies of short duration, since these studies are challenging to execute.

Does surgical weight loss differ substantially from nonsurgical weight loss through medication, diet, and exercise?

Grunvald: The similarity between bariatric surgery and pharmacologic weight loss is centered on the concept that both are biological therapies for a biological disease, not a lifestyle problem. Diet and exercise alone have very limited effectiveness in the long term, in part because biological forces work to defend against sustained weight loss. Both anti-obesity pharmacotherapies and MBS modulate the pathophysiology of obesity to suppress the natural adiposity set point.

Will clinicians be able to apply these results in practice?

Grunvald: It is premature to use this tool widely in the clinic for the purpose of predicting weight loss outcomes after bariatric surgery. However, I would recommend that clinicians routinely ask patients about satiety, satiation, and cravings, or hedonic eating, throughout their weight loss journey after MBS. I think that a patient's subjective report of their control of eating is a very good surrogate for understanding how their physiology changes over time.

In my practice, if a patient has suboptimal weight loss or has significant recurrent weight gain, I routinely discuss these "symptoms" and act expeditiously to consider treating the underlying biology, usually with anti-obesity medications, but along with lifestyle support, of course.

If our findings are supported by larger studies with longer follow-up and if this and similar tools perform well in predicting successful weight loss, further opportunities may open up for physicians and, what is most important, for our patients.

Those short but comprehensive questionnaires could help a physician do an assessment that could potentially change the clinical approach and apply modifications to the patient's pharmacological and behavioral intervention even remotely without the need of an in-person encounter.

The instrument could also be potentially linked to a set of recommendations aimed at improving food choices and eating habits. It would help our patients monitor their progress, correlate it with their lifestyle choices, apply modifications, and feel in control over their health -- as well as realize that their healthcare provider is supporting them in their weight loss journey.

What's the next step in your research?

Grunvald: Our results with the CoEQ need to be replicated and prospectively validated with larger samples, different populations at multiple sites, and perhaps for longer periods of time. It would also be attractive to correlate these CoE attributes with other biological measures -- for example, hormone levels, gastrointestinal motility, and functional brain scans. Similar studies should be performed after other procedures, such as Roux-en-Y gastric bypass as well.

Moreover, we now test select patients with severe obesity for specific genetic mutations that may be associated with propensity for weight gain, even after bariatric surgery. Correlating our results with these genetic results would also be useful.

Predicting weight loss outcomes after bariatric surgery remains challenging, and currently there are no good predictive tools. Many healthcare professionals and patients place a great emphasis on lifestyle control for success after surgical therapies, as they should since that is the foundation for all weight loss therapies.

But genetics and physiology play a very important role, and these should be further investigated.

Read the study here and expert commentary about it here.