Concentration of metabolites and fats return one year after gastric bypass

The biggest metabolic changes after gastric bypass happen directly after surgery and just one year after the operation, the concentration of metabolites and fats return to almost the same levels as before the procedure, according to researchers from Lund University in Sweden.

Figure 1: PCA score plots for lipidomics data acquired in positive (ESI+; 80 annotated lipids) and negative (ESI-; 46 annotated lipids) ESI mode. PCA was conducted on (A,B) metabolite levels and (C,D) changes in metabolite levels (effects) within defined time ranges: short term (2 months vs. baseline), long term (12 vs. 2 months), cumulative (12 months vs. baseline), and reference (baseline vs. baseline). (E,F) Changes in the lipidome for individual study participants are illustrated in the score trajectory plots, with trajectories estimated as described in Figure 1. P values are shown for the factor time, using the model: score ~ Time + T2D + Sex + Time:T2D + Time:Sex, nested by patient ID. ***p < 0.001; NS, p > 0.05. ESI, electrospray ionization; NS, not significant; PCA, principal component analysis; T2D, type 2. Credit: Obesity (2023). DOI: 10.1002/oby.23864

Previous research has shown that the majority of those who undergo surgery regain weight within five years of a gastric bypass operation however, it has not been established what happens to the metabolism of those who have had a bariatric procedure. Subsequently, the researchers studied the metabolism of overweight individuals before and after they had a gastric bypass operation. The study shows that the biggest changes happened straight after the procedure. One year later, the concentration of metabolites and fats among all the participants were nearing the same levels as before the operation.

"Just following up on the weight of people can be a blunt instrument for studying the effects of the procedure,” said Dr Peter Spégel, associate professor of molecular metabolism at Lund University, who led the study. “Our study provides a greater understanding of what happens to the metabolism in connection with a gastric bypass operation."

The study was based on data from 148 people with and without type 2 diabetes who underwent a gastric bypass operation in Sweden. Blood samples were collected from participants just before the procedure and on at least two occasions after the operation. Their body mass index (BMI) was measured before the operation and on three occasions afterwards.

The researchers conducted detailed analyses of fats and metabolites in the blood. Just one year after the operation, some of the participants were back at exactly the same levels as before the surgery, whereas the reversion was not as marked for others.

"We could see the changes while the participants still had a low BMI after the operation. By studying metabolism, we can obtain a clear indication that unhealthy changes are on the way,” explained Professor Nils Wierup, professor of neuroendocrine cell biology at Lund University and one of the main authors of the article. “We hope that the knowledge can be used in follow-up so that preventive measures can be put in place.”

The levels of certain polyunsaturated fats increased straight after the operation to then fall and approach the same levels as previously. The study also showed a reduction in the concentration of a certain type of amino acids after the operation and then a subsequent rise. The levels of these amino acids are usually high in individuals with insulin resistance and carry an increased risk of developing type 2 diabetes.

"One conclusion we draw is that the risk of developing type 2 diabetes is considerably reduced after the operation among individuals who do not have the disease, but one year later we see an increased risk again,” added Spégel. “Among individuals who already had type 2 diabetes at the time of the surgery, we see a remission of the disease, but the risk of the disease returning then increases over time.”

Individuals who undergo surgery for obesity need to lose weight before the operation by means of a diet. A previous study by the same research team examined the effects of a low-calorie diet and a gastric bypass operation separately. The study showed that the diet had the biggest effect on metabolism, whereas the surgery led to quite small changes. The researchers' latest study now shows that for many people, the positive effects on metabolism subside as soon as one year later.

"We need more and larger studies in order to draw reliable conclusions. One advantage of bariatric operations is that a majority of people with type 2 diabetes see a remission of their disease afterwards,” concluded Wierup. “And even though a large percentage of individuals who undergo this procedure gain weight afterwards, it's usually not a return to the same weight as before. In the future, we want to take a closer look as what happens to metabolism on an individual level, as this can vary.”

The findings were reported in the paper, 'Metabolic remission precedes possible weight regain after gastric bypass surgery', published in the journal Obesity. To access this paper, please click here