Low-carbohydrate diets have become increasingly popular for weight loss and blood sugar control, but their impact on cholesterol levels can vary dramatically from person to person. New research presented at NUTRITION 2026, the annual meeting of the American Society for Nutrition, suggests that genetics may play a key role in determining who experiences a rise in cholesterol and who does not. The findings indicate that saturated fat, which can make up a larger proportion of some low-carb diets, may interact with a person's genetic makeup to increase levels of low-density lipoprotein (LDL) cholesterol, often referred to as "bad" cholesterol because of its association with heart disease.
"Our findings suggest that some individuals may be more sensitive to the LDL cholesterol-raising effects of saturated fat, particularly in the context of a low-carbohydrate diet, because of their genetic background," said Alexa Barad, Ph.D., RDN, a postdoctoral scholar at Stanford University School of Medicine, in a statement. Barad said the findings highlight that people can respond very differently to the same diet, suggesting that nutrition advice is often oversimplified. While some people may see their LDL cholesterol rise on a low-carb diet, others may experience little or no change.
Christine Bishara, a New York based integrative medical doctor who specializes in gut health, who was not involved in the study, said the results reinforce something they she has seen many times in her 30 years as a practicing physician. She said: "There is no 'one size fits all' when it comes to what diet works best for everyone." Previous research has shown that healthy low-carbohydrate diets can help some people lose weight and improve blood sugar control. However, their effects on LDL cholesterol have been less predictable.
Researchers wanted to find out whether genetic information could help identify people who are more likely to benefit from reducing carbohydrates and those who may instead experience a potentially harmful increase in LDL cholesterol. To investigate, they analyzed data from DIETFITS, a randomized controlled trial involving more than 600 adults who followed either a healthy low-carb diet or a healthy low-fat diet for one year. The original study found no significant difference in weight loss between the two approaches.
For the new analysis, researchers focused on 431 participants for whom genetic information was available. They examined the relationships between genetic background, saturated fat intake, diet type and changes in LDL cholesterol over the first six months of the study. Bishara notes that low carb can mean different things with some people opting for fewer carbohydrates, high protein and high saturated fat.
She told Newsweek: "These diets can certainly help with weight loss, but when they are very low in fiber and plant diversity, they may not provide the nutrients and fermentable fibers that many beneficial gut bacteria need to thrive. "A low-carb diet built around vegetables, berries, nuts, seeds, olive oil and other whole foods is very different from one built around butter, bacon and other sources of saturated fat. Those differences matter not only for cardiovascular health, but for the gut microbiome as well.
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