Scientists have found out which carbohydrates more strongly activate immunity after weight loss

Scientists from NYU Langone Health and other U.S. research centers found that a diet high in refined starch after weight loss activates immune system cells more strongly than a diet with added sugar. The study was conducted on people who had lost approximately 15% of their body weight on a very low-carbohydrate diet before the experiment. The results were published in the journal Cell Press Blue.

The study involved 54 people with overweight or obesity who did not have cardiovascular diseases or diabetes. After losing weight, the volunteers were divided into three groups: one continued the very low-carbohydrate diet, while the other two received a high-carbohydrate diet — in one case the source was starch from refined grain products, and in the other — added sugar. The diets were equal in caloric content, and the experiment lasted ten weeks.

The most notable changes were found by the researchers in participants who received refined starch. They showed increased activity of several types of immune system cells, including natural killer cells — cells involved in destroying infected and altered cells — monocytes, T-lymphocytes, and neutrophils. Gene activity analysis also revealed enhanced processes associated with innate and adaptive immunity, as well as defense against bacteria and fungi. Meanwhile, the diet high in added sugars led to opposite results. After ten weeks, the indicators of immune and metabolic process activity in this group generally decreased compared to baseline levels.

One possible mechanism, according to the scientists, involves the complement system — a part of the immune defense that helps the body recognize and destroy foreign objects. In the refined starch group, levels of adipsin, or complement factor D, which participates in activating this mechanism, were elevated. The authors suggest that rapid glucose spikes after meals may be linked to enhanced complement activity and subsequent activation of immune cells.

The scientists note that the results cannot be generalized to all people — the experimental conditions were too specific (study participants had obesity and were on a diet). The authors believe that the obtained data demonstrate the importance of carbohydrate composition for immune processes.