Gastric Bypass Surgery: Appetite Drop, Food Aversion Common Afterward

Marlene Busko

April 25, 2014

Following gastric-bypass surgery, almost all patients will have a smaller appetite, but they will also probably find that some foods no longer taste or smell the same, a new study reports. Moreover, patients who develop a dislike for foods they enjoyed before — often meat — lose more weight than their peers.

These findings are based on questionnaire replies from 103 obese patients who underwent Roux-en-Y gastric-bypass surgery at a center in the United Kingdom. After their surgery, almost all patients (97%) reported a drop in appetite, and many reported that some foods tasted differently (73%) or smelled differently (42%).

"This was a snapshot study in time trying to put some sense to anecdotal patient comments about how their taste and smell senses have changed," senior author David J. Bowrey, MD, from the Leicester Royal Infirmary, United Kingdom, told Medscape Medical News. "The good part…is that patients who had aversions…to certain foods had greater weight loss than some of the other patients."

As part of the informed-consent process, clinicians should tell patients about these potential side effects, he said.

The study was published online March 8 in Obesity Surgery.

"Something That Isn't Mentioned"

As bariatric surgery has evolved and been shown to be safe and provide effective, long-term weight loss, clinicians have shifted attention to focus more on how the procedure affects quality of life.

Recent findings from the 3-year randomized STAMPEDE trial, which indicated bariatric surgery is better than intensive medical therapy alone for controlling blood sugar in the obese with uncontrolled diabetes, showed, for the first time, that there was a marked improvement in quality of life among surgery patients. However, this study did not address the issue of taste or smell of foods postprocedure.

Dr. Bowrey explained that bariatric-surgery patients are typically counseled about how the surgery will have a dramatic effect on their stomach (which will reduce to about the size of a golf ball) and the size of meal they will be able to manage.

But they noticed at their center that in support-group meetings, patients who had undergone this surgery who were counseling others would say, for example, "Something that isn't mentioned is a change in taste and smell." Little has been reported in the literature about this potential side effect, they note.

So to investigate this issue, Dr. Bowrey and colleagues invited all those who had undergone Roux-en-Y gastric-bypass surgery at their center from 2000 to 2011 to reply to a previously validated 33-question survey (Surg Obes Relat Dis . 2006 2:440-444). The patients had a median body mass index (BMI) of 51 (range, 36 – 97) when they underwent the surgery.

Over half (55%) of the invited respondents replied, 14 men and 89 women, who were, on average, 45 years old. About three-quarters had undergone bypass from 1 month to 3 years earlier, while about one-quarter had had surgery 3 to 12 years ago.

The respondents noticed a change in taste and smell in a wide variety of foods. They were roughly equally split over whether foods tasted more or less sweet, salty, or sour.

One-third said they no longer liked the taste of chicken, beef, sausages, lamb, ham, or bacon. About 1 in 10 reported an aversion to starchy foods (pasta, rice, bread, pastries),  dairy products (milk, yogurt, cheese, eggs, ice cream), or fast food (burgers, potato chips). Fewer respondents no longer liked the taste of food and drink such as tea, coffee, fried foods, chocolate, vegetables, and fruits.

Those who developed food aversions typically lost about 8 kg more than the other respondents, and they had a greater drop in BMI (20 vs 17).

Potential Mechanisms

A combination of gut-hormone and central-nervous-system effects likely account for these sensory changes, the researchers speculate.

The vagus nerve, which regulates stomach emptying, is not likely to be involved, since patients who undergo stomach-cancer surgery, where the vagus nerve is cut, experience similar food taste and smell changes as those who undergo bariatric surgery, where vagus-nerve function is preserved, Dr. Bowrey said.

To explain the inconsistent pattern — where patients experience a heightened, reduced, or unchanged sense of smell or taste — they hypothesize that the surgery disturbs smell and taste, which is followed by oscillating hypersensitivity and hyposensitivity, before these senses are reset at new, steady-state levels.

Dr. Bowrey receives research grant funding from Fresenius-Kabi and Nutricia for research unrelated to this work. The coauthors have no relevant financial relationships.

Obes Surg. Published online March 8, 2014. Abstract

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