ByLucy Notarantonio
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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
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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.”
Why Low-Carb Diets Affect People Differently
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 otherrdiovascular health, but for the gut microbiome as well. “
Genetics and Saturated Fat Linked to LDL Increases
Among participants assigned to the low-carb diet, those with a genetic predisposition to higher LDL cholesterol were more likely to experience an increase in their cholesterol levels
The researchers found that greater sensitivity to saturated fat appeared to be driving this pattern. Participants with the highest genetic risk experienced the largest increases in LDL cholesterol when consuming more saturated fat. The same relationship was not seen among people following the low-fat diet
Rather than focusing on individual genetic variants, researchers used a polygenic score, which combines thousands of genetic variants across the genome to estimate a person’s overall genetic tendency toward higher or lower LDL cholesterol
Barad said polygenic scores could eventually help clinicians identify people who may be more likely to experience unfavorable cholesterol changes after making dietary adjustments
Monitoring Cholesterol May Be Key
Barad said the findings offer a practical reminder that dietary changes do not affect everyone in the same way
Genetic testing is not necessary to apply the study’s message, she noted. Instead, people should pay attention to how their own bodies respond to dietary changes rather than assuming a particular eating plan will produce the same results for everyone
Additional research will be needed to confirm the findings and determine whether they apply across more diverse populations
Current dietary guidelines generally recommend limiting saturated fat to less than 10 percent of daily calories and choosing unsaturated fats where possible. For people following a low-carbohydrate diet, Barad suggested emphasizing foods such as nuts, seeds, olive oil and avocado instead ofy cuts of meat and processed meats. Researchers said this approach may help reduce the risk of an unfavorable cholesterol response
Contact Newsweek editors on this story: Charlotte Nisbet and Tony Phillips
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