Low-carbohydrate diets remain a popular choice for weight loss, with data indicating that 7 percent of Americans followed such a diet in 2024. Research has also highlighted their potential benefits, including a recent study showing that a strict keto diet outperformed other weight-loss approaches on several markers of metabolic health and liver function. However, sustaining a low-carb lifestyle over the long term is challenging, and many individuals may wish to transition back to less restrictive eating patterns once they reach their health or weight goals.
So, what actually happens when you reintroduce carbohydrates after a period of low-carb eating? A new study published in Cell Press Blue investigated this question, and the findings suggest that the consequences depend significantly on the type of carbohydrates you consume.
Study Design: From Low-Carb to High-Carb
Researchers, led by a team from NYU Langone Health, analyzed data from a controlled feeding experiment. The initial group included 54 participants—both men and women aged 18 to 50—who were overweight or obese but did not have cardiovascular disease or diabetes.
During a run-in phase, all participants received a very-low-carbohydrate diet consisting of delivered prepared meals, designed to create a substantial 40 percent calorie deficit to induce weight loss. After achieving approximately 15 percent weight loss, participants were randomly assigned to one of three dietary groups for a 10-week period.
One group continued on the very-low-carbohydrate diet, while the other two groups received different high-carbohydrate diets. Both high-carb diets had identical macronutrient compositions—57% carbohydrate, 25% fat, and 18% protein—but they differed in one key aspect: one diet derived 20 percent of its total energy from starch in refined grains, while the other obtained the same proportion from added sugar.
Key Finding: Starch from Refined Grains Linked to Inflammation
Blood test analyses from approximately 40 participants revealed a striking difference between the two high-carb groups. The high-starch diet triggered signs of increased inflammation compared to the other two groups, activating a range of immune cells and inflammatory pathways. Specifically, participants on the high-starch diet showed higher levels of circulating adipsin—a signaling protein associated with inflammation—as well as increased activation of immune cells including CD4+ T cells and neutrophils.
Additional evidence from a mouse experiment supported these findings. Mice fed maltodextrin (derived from starch) after fasting exhibited increased immune activity, further suggesting that starch can influence the immune system.
