Why weight loss drugs don’t work the same for everyone: The frontier of emotional eating

The new generation of obesity drugs achieves astonishing weight loss, as much as 24% in their most modern versions. But when evaluating them, we tend to focus on the success stories: the “until” and not the “from.” However, not everyone responds equally to treatment, and a recent study may have pointed to the reason. A group of scientists monitored 92 people with diabetes in Japan during their first year of treatment with weight-loss drugs and discovered that the patient’s psychology can affect the success of these therapies. People who overate at the sight or smell of tasty food were more likely to respond well to the drugs over the long term, while those who overate for emotional reasons were less likely to do so.

This finding could help personalize treatment for future patients. “Assessing eating behavior patterns will help predict who will benefit most from therapy with GLP-1 receptor agonists [such as Ozempic],” said Professor Daisuke Yabe of Kyoto University, senior author of the article published in Frontiers in Clinical Diabetes and Healthcare.

Overall, participants experienced a statistically significant reduction in body weight over the course of the year. However, some differences in outcomes were observed based on eating behaviors. At three months, participants reported fewer behaviors associated with external or emotional eating. But at 12 months, emotional eating behaviors returned to baseline levels. “One possible explanation is that emotional eating is influenced by psychological factors that are not addressed by GLP-1 receptor agonists,” Yabe stated.

“The study has limitations,” notes Cristóbal Morales, an endocrinologist at Vithas Hospital in Seville who is not involved in this new research. “It’s small and not a clinical trial, as it relies on patient data. But what it says makes sense and supports numerous similar studies.”

One factor worth highlighting is that it stems from the idea of obesity in the plural. A group of researchers led by Andrés J. Acosta, an endocrinologist at the Mayo Clinic (USA), distinguished four types. They then proposed classifying obesity not only numerically — using scientifically questioned criteria, such as BMI — but also by phenotypes that combine physiological and behavioral traits. They then began to talk about emotional hunger (“those who seek a dopaminergic reward through food,” explains Morales), brain hunger (“the hypothalamic regulation of satiety is sometimes impaired”), hungry gut (“when gut-brain communication doesn’t work properly”), and people with slow burn (who have very low resting calorie expenditure). “What we see in the clinic is that it’s usually a mixture; I don’t know anyone who has a pure phenotype,” the expert notes. But this classification can help distinguish the causes of a complex disease.

Combining drugs and psychotherapy

Weight-loss drugs act on appetite and hedonic pathways, which can reduce impulsive eating behaviors. However, if emotional eating is linked to trauma, depression, anxiety, or other emotional problems, the ideal treatment should combine pharmacology and specialized psychotherapy. This was the conclusion of a meta-analysis conducted at the University of Staten Island (USA) on people with binge eating disorders and bulimia nervosa.

Another study from the University of Pisa (Italy) analyzed more than 300 candidates for bariatric surgery. They were given various tests to determine which phenotype they fit. Those who scored high on the emotional eating scale — that is, those whose hunger was more closely linked to emotions — were much more likely to regain weight after the procedure. The authors suggested the need to analyze the psychological dimension in these patients.

Cinthya González García, a psychologist specializing in nutrition and obesity at the Aure psychological clinic in Madrid, has been working on this for years. “Weight loss doesn’t depend solely on what happens in the body,” she explains in a message exchange. “The relationship with food is perhaps the factor that has been least addressed medically, but it is key to long-term, sustainable weight loss.” González welcomes the study, stating that it is very similar to what she has seen in her practice. “In my experience with patients who undergo bariatric surgery, the outcome is similar. Initially, surgery helps almost everyone lose weight. However, those who engage in emotional eating do worse in maintaining weight loss over the long term.”

Strategies against the rebound effect

Weight loss drug treatment has relatively low adherence. Despite experts advocating for lifelong adherence, more than half of patients abandon it after a year. Considering these data, it seems clear that psychological treatment would be advisable.

The bariatric surgery referral criteria manual, published by the Spanish Ministry of Health in 2016, establishes that eating disorders must be ruled out or pretreated. Many public and private hospitals require a psychological report before performing this procedure. Drug treatment is much less invasive and does not carry the same risks as surgery. However, the lessons learned from that experience can be applied to this one. Taking into account not only the patient’s morphology, but also their psychology, can make a difference. A 2021 study published in the scientific journal Obesity found that 79% of patients with phenotype-guided treatment lost weight, compared to 34% in those who did not use this guideline.

“GLP-1 agonist drugs reduce physical appetite, but not emotional hunger,” González summarizes. This can lead to significant initial weight loss and a long-term rebound, as the cause of obesity isn’t being addressed; it’s merely a temporary band-aid. “If the psychological aspect isn’t addressed, over time or after stopping the medication, the emotional patterns reappear. In these cases, even if the body feels full, the mind continues to seek relief in food,” the specialist concludes.

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