The Cholesterol-Diet Mystery: Genetics Holds the Answer

For years, nutritionists have faced a puzzling question: why can two people follow the exact same eating plan and get completely different results? A new study sheds light on this phenomenon, offering hope for tailored dietary advice.

The DIETFITS Study and Precision Nutrition

According to reports from Infobae, Libertad Digital, and El Economista, the findings were presented by Alexa Barad, PhD in nutritional sciences and postdoctoral researcher at Stanford University, at the NUTRITION 2026 congress held from July 25 to 28, 2026 in National Harbor, Maryland, USA.

The work is based on data from the clinical trial DIETFITS, a study that followed over 600 adults for one year on two types of healthy diets: low-carb or low-fat. For this new analysis, researchers examined 431 participants with available genetic data, evaluating the relationship between their genotype, saturated fat intake, and changes in LDL cholesterol after six months on the diet.

The Role of Genes: The Polygenic Score

What sets this research apart is its genetic approach. Instead of looking at individual variants, scientists combined thousands of variants across the genome to build a polygenic score. This score estimates each person's natural tendency to have higher or lower LDL cholesterol levels.

Results showed that among those following the low-carb diet, individuals with a genetic predisposition toward high LDL cholesterol were more likely to see that value increase. This increase was linked to a heightened sensitivity to saturated fat (found in butter, red meat, and cold cuts). In contrast, people on the low-fat diet did not show the same patterns.

Practical Tips for a Healthier Life

According to the American Society for Nutrition (ASN) press release, in the future doctors could use these polygenic scores to identify who is most likely to experience adverse LDL cholesterol responses to certain diets. However, even without a genetic test, the lesson is clear: every individual reacts differently, and it is essential to monitor how your body responds to changes.

General dietary guidelines recommend limiting saturated fat intake to less than 10% of daily calories. For those choosing a low-carb diet, Dr. Barad suggests prioritizing healthier fat sources:

• ✅ Healthy fats: nuts, seeds, olive oil, and avocado.
• ❌ Fats to limit: butter, beef fat, fatty cuts of meat, and cold cuts.

Sources: Infobae, Libertad Digital, El Economista, La Razón.