After undergoing weight-loss surgery, adults with obesity were less susceptible to food marketing tactics than they were pre-surgery, new research from France found, suggesting that responsiveness to food marketing is not a predisposed personality trait and providing evidence of a new psychological effect of the procedure.

In a study of adult women in France, published Jan. 23 in the Journal of Consumer Psychology, researchers investigated the effectiveness of food marketing claims on women who were either obese or of average weight.

Marketing tactics tend to frame food and portions as being healthier than they actually are, and these ploys are often accused of increasing obesity in the population, the authors of the paper said. It’s suggested that if food marketing contributes to obesity, people who are more easily influenced by marketing tactics would be more at risk of becoming obese. The study found that obese people were more responsive to unhealthy food marketing than people with an average weight.

But the study found that the obese participants’ responsiveness to unhealthy food marketing decreased over time following their bariatric surgery procedure, until their responsiveness was nearly in line with that of the women who were not overweight. This was measured with three tasks that gauged the influence of marketing framing tactics that have been shown to lead to biased food judgments and decisions.

“Psychology has long been interested in the interplay between personality and the environment,” Pierre Chandon, a professor of marketing at INSEAD and co-author of the paper, told The Academic Times.

“We show that the higher responsiveness to food marketing tactics of people with obesity is not purely the result of a stable individual disposition, such as low self-control or high reward sensitivity, as it had been suggested by earlier research,” he said.

Bariatric surgery procedures such as gastric bypass or adjustable gastric banding are undertaken by 600,000 people every year around the world, and Chandon said the current study demonstrates the value of researching the psychological effects of these surgeries. Previous studies have found that bariatric surgery can increase preferences for healthier food by altering reward and taste processing, the authors noted. 

Through a collaboration with the nutrition department of the Pitié-Salpêtrière hospital in Paris, the research team recruited a sample of 73 women with obesity who were scheduled for weight-loss surgery, a separate sample of 29 overweight women who did not have plans for weight-loss surgery, and a sample of 41 women who were not overweight. 

The three marketing framing tactics included in the study were brand framing effects, in which people incorrectly estimate the calorie content of foods positioned as “healthy”; size labeling effects, in which the same portions are described as “large” or “small”; and size range effects, in which people are influenced by the range of sizes available.

All study participants performed the same tasks, and the patients with obesity were tested before surgery, three months after surgery and twelve months after surgery. The group of overweight women who were not having surgery was only surveyed once, and the group of women who were not overweight was surveyed twice, six months apart. Data collection occurred between 2011 and 2017.

The participants were asked to estimate the number of calories in branded snacks, including some brands that are typically marketed as healthy and some that are typically marketed as indulgent. For example, one can of Minute Maid 100% apple juice was 149 calories, and one can of Coca-Cola was 139 calories. The “healthy” snacks in the task actually contained 22% more calories, 14% more fat, 33% more carbohydrates and 8% less protein than the “indulgent” snacks.

The patients who were scheduled for weight-loss surgery underestimated the calorie count of the “healthy” foods by 15.1% in the first survey, and they overestimated the calorie count of the “indulgent” foods by 49.4%. Twelve months after the surgery, the figures were no longer statistically different between patients with obesity and those without. The calorie estimates of obese patients who had bariatric surgery also improved significantly over time compared to the obese patients who did not have surgery.

All the participants were also shown menus of fast-food restaurants they were unfamiliar with and were tested on size labeling effects and size range effects by choosing fries and drink options. The three menus featured identical portion sizes of fries, but they were labeled differently. The 71g, 117g and 154g orders of fries were labeled small/medium/large on the first menu, mini/small/medium on the second and medium/large/extra-large on the third.

Participants had to choose the size of fries that they wanted. People chose larger portions when the portions were described as mini/small/medium, indicating that the labels could successfully manipulate the perceived healthiness of the portions of fries.

Overall, the study found that the responsiveness of people with obesity to the tested marketing tactics decreased 12 months after their bariatric surgery, down to the level of people of average weight.

“This suggests that responsiveness to food marketing is not a stable individual predisposition, since it is influenced by bariatric surgery. It also provides evidence for a new psychological consequence of bariatric surgery — reduced responsiveness to food marketing,” Chandon said.

“More generally, our study provides novel evidence for a reciprocal relationship between obesity and sensitivity to environmental influences, rather than the standard unidirectional causal path from marketing to obesity,” he continued.

Chandon noted that even though the study was conducted in France, the food marketing tactics that they analyzed were originally tested in the U.S. In participants of average weight, the team found that these tactics tended to have a relatively lower effect on French adults than on Americans, indicating that results may be even stronger if this study was replicated in the U.S.

The authors suggested that future research should examine how bariatric surgery and weight loss may influence obesity-related dysfunctions in metabolic and hormonal signaling processes. And they recommended that other studies include a more diverse sample of patients with obesity, including men and people of different ages.

“What remains also unclear is whether the decrease in responsiveness to marketing that followed bariatric surgery is strictly the result of weight loss, or whether it is also the result of the host of the biological and psychological modifications induced by the surgery itself and that would not occur through non-surgery-induced weight loss, such as changes in people’s own beliefs about the cause of obesity,” the authors said.

The study, “Obesity and Responsiveness to Food Marketing Before and After Bariatric Surgery,” was published in the Journal of Consumer Psychology on Jan. 23. Pierre Chandon, the director of the INSEAD-Sorbonne University Behavioural Lab, was the lead author. Yann Cornil, of the University of British Columbia, Hilke Plassmann, of INSEAD, Michèle Chabert, of the Ecole Pratique des Hautes Etudes institute in France, and Judith Aron-Wisnewsky, Christine Poitou-Bernert and Karine Clément, all of Sorbonne Université, served as co-authors.

Correction: A previous version of this story mischaracterized the categories of participants in the study. The error has been corrected. This story has also been updated to include new details about the research.