Also known as weight loss surgery, bariatric surgery is a procedure carried out to help people who are severely or morbidly obese, to lose weight.

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Types of Bariatric Surgery

There are four types of bariatric surgery that may be performed:

• Gastric band procedure – The size of the stomach is reduced using a band placed around the stomach. This reduces the amount of food a person needs to eating order to feel full.
• Gastric bypass – This involves dividing the stomach into a smaller upper section and larger lower section. The smaller section is then connected to part of the small intestine. Food only passes into the small stomach and this part of the small intestine, bypassing the remaining stomach and bowel. This reduces the amount of calories absorbed when food is passed through the digestive system, as well as decreasing the amount of food a person needs to eat in order to feel full.
• Sleeve gastrectomy – Here, a part of the stomach is removed to reduce its size and limit the amount of food intake required for a person to feel full.

Sensory Changes Following Surgery

Change in the taste, smell or tolerance of food following bariatric surgery is a common phenomenon. One study showed that as many as 97% of patients experience at least one such change following these surgeries.

Fortunately, the changes often benefit patients, with research showing that they help people to lose more weight than people who do not experience any changes.

According to a study conducted by researchers from the University Hospitals of Leicester, which included 103 patients who underwent gastric bypass, 73% reported changes in the taste of food and almost 50% reported changes in smell.

The most commonly reported taste changes were heightened sensitivity to sweet food, sour food and fast food.

Some patients also developed an oversensitivity to sweetness in protein shakes, which can be a problem should patients need to follow a liquid-only diet after their operation. If this happens, a patient should talk to their doctor to ensure their dietary requirements s are being met.

Eating behaviors may also change following bariatric surgery. Patients may be less likely to find emotional eating is a problem and eating cues may have less impact.

Evidence also suggests that the mood-altering effect of sweet foods may be reduced, with patients less likely to experience a “sugar high” after a bariatric procedure. The tendency to eat purely as a matter of habit may also fade.

Cause

The exact cause of these changes following bariatric surgery is not yet clear, but many researchers suspect that fluctuating gut hormones and the effect these have on the nervous system may play a role.

The central nervous system relays hunger, craving and satiety messages between the brain and gastrointestinal tract.

The nerves that carry these messages are affected when a part of the stomach  removed, which impacts a person’s sense of taste, smell and satiety.

Ghrelin is a hormone that plays an important role in hunger. A reduced calorie intake and weight loss leads to increased ghrelin production, which makes people feel hungry.

In contrast, weight loss as a result of bariatric surgery leads to decreased ghrelin production, therefore reducing hunger and food intake following the procedure.

Another important hormone, which is involved in satiety, is leptin. This relays messages between the gut and brain about how full a person is and determines whether calories are burned or stored as fat.

Losing weight is thought to increase a person’s sensitivity to these messages, resulting in a person feeling full more easily after eating only small amounts of food.
Reviewed by Afsaneh Khetrapal BSc (Hons)