The Roux-en-Y gastric bypass (RYGB) involves separating the upper part of the stomach into a smaller pouch, which is then directly connected to the small intestine.
This procedure allows the individual to feel full after eating less.
It is usually undertaken by people with severe obesity who have seen no improvements following other treatments.
“People who have this surgery,” explains Prof. Patricia DiLorenzo, based at Binghamton University in New York, “are what we call morbidly obese, meaning that they are at least 100 pounds overweight, and in many cases are diabetic. It’s life or death for them.”
Prof. DiLorenzo and colleagues recently decided to look into one particular aspect tied to this type of bariatric surgery: how an individual’s tastes in food before and after this procedure influence its long-term success rates.
Some studies have already suggested that a person’s taste and odor preferences pre- and post-operation tend to change, and that this may influence their weight loss trajectory.
The researchers conducted their study in 195 participants with a body mass index (BMI) over 30, who were either about to receive or had already undergone RYGB surgery. The team’s findings now appear in the journal PLOS ONE.
Different taste preferences and weight loss
The researchers asked the participants to indicate their food and odor preferences before and after RYGB surgery using a method called the Self-Assessment Manikin, which evaluates a person’s responses of pleasure when faced with a particular object.
In this assessment, the volunteers responded to foods associated with the five tastes (sweet, sour, salty, bitter, and umami), and to four distinctive odors, two of which were food-related (coffee and banana), and two of which were non-food related (rose and gasoline pump).
Prof. DiLorenzo and colleagues also collected participants’ BMI data, both before and after bariatric surgery.
Somewhat surprisingly, a significant number of participants indicated that before the surgery, they had enjoyed the taste of junk foods such as pizza, but that after it, they became more partial to more healthful foods such as salads.
“Most people before their surgery, their favorite foods are just what you’d expect — ice cream, French fries, burgers, pizza,” Prof. DiLorenzo says.
“But afterwards, their favorite food was salad, for example. Twenty percent of people said that their favorite foods were vegetables. Those people — the ones who said they changed their taste preferences — lost the most weight.”
Prof. Patricia DiLorenzo
Transitioning from sweet to bitter
Another fascinating finding indicated that people who enjoyed the smell of coffee more after their procedure also tended to lose more weight.
The researchers hypothesize that since coffee and vegetables have an underlying bitter flavor, some of the participants’ taste preferences had shifted from sweet (associated with high-fat foods) pre-operation to bitter post-operation.
Nevertheless, Prof. DiLorenzo and team also note that, over time, people tend to shift back to the same flavor preferences they had before the bariatric surgery. Also, individuals tend to lose less weight as time goes on after the procedure.
“The lion’s share of the weight is lost in the first year. After that, your weight stabilizes,” says Prof. DiLorenzo.
Still, she emphasizes that bariatric surgery is the best way to induce weight loss for many people with obesity and also explains that most people manage to maintain a more healthy weight following the intervention.
“People have the view that most people gain the weight back after RYGB surgery, and that’s not true. Eighty percent of the people keep the weight off. In Western medicine, this is the most effective treatment for obesity,” Prof. DiLorenzo adds.