Low-carbohydrate diets have become very popular because many people use them to lose weight or improve blood sugar levels.
While some people see excellent results, others notice an unexpected rise in their cholesterol levels.
A new study suggests there may be an important reason for these different experiences: our genes. The research was presented at NUTRITION 2026, the annual meeting of the American Society for Nutrition.
Researchers from Stanford University School of Medicine found that a person’s genetic makeup may influence how their body responds to the high amounts of saturated fat that often accompany low-carbohydrate diets.
Saturated fat is commonly found in butter, fatty meat, processed meat and some full-fat dairy products. Although these foods are frequently eaten on low-carb diets, they do not affect everyone in the same way.
To investigate this question, the scientists analysed information from the DIETFITS clinical trial, in which more than 600 adults followed either a healthy low-carbohydrate or healthy low-fat diet for one year. For this analysis, the team examined 431 participants who also had genetic information available.
Instead of studying only one or two genes, the researchers used a polygenic score that combined thousands of genetic differences across the entire genome. This score estimated whether a person was naturally more likely to have higher LDL cholesterol, often called ‘bad’ cholesterol because high levels increase the risk of heart disease.
The results showed that people following the low-carbohydrate diet who had a higher genetic risk were much more likely to experience increases in LDL cholesterol, especially if they consumed larger amounts of saturated fat. In contrast, participants eating a healthy low-fat diet did not show the same pattern.
The findings help explain why debates about low-carb diets often produce conflicting opinions. Some people can follow the diet with little change in cholesterol, while others experience a substantial increase. According to the researchers, both experiences can be correct because genetic differences influence how each person’s body processes saturated fat.
Although the study did not suggest that everyone should avoid low-carbohydrate diets, it highlighted the importance of choosing healthier fat sources. Foods such as nuts, seeds, olive oil and avocados provide more unsaturated fats, which are generally considered better for heart health than butter or fatty processed meats.
The researchers believe genetic testing may one day help doctors recommend diets that are better matched to each person’s biology. Until then, anyone starting a low-carbohydrate diet should have their cholesterol checked regularly rather than assuming the diet will affect them the same way it affects someone else.
This research was presented at a scientific conference and further studies will be needed before the findings are confirmed in larger and more diverse populations. Even so, it provides important evidence that nutrition is not one-size-fits-all and that personalised dietary advice may become more common in the future.
Overall, the study offers a balanced message. Low-carbohydrate diets may provide real benefits for some people, but they are not automatically the best choice for everyone. Monitoring cholesterol, limiting saturated fat and working with healthcare professionals remain sensible steps while researchers continue to explore how genes influence our response to food.
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