New research presented at NUTRITION 2026 suggests genetics determines who is sensitive to the LDL-raising effects of saturated fat on a low-carbohydrate diet.

Few nutrition debates are as stubborn as the one over low-carb eating and cholesterol. Critics warn that diets heavy in fat will drive LDL cholesterol — the so-called “bad” cholesterol — to dangerous levels. Devotees counter with their own lab results showing nothing of the sort. Both sides have anecdotes. The research literature has been mixed.

A new analysis presented at NUTRITION 2026, the annual meeting of the American Society for Nutrition, suggests the two camps may both be right. The deciding factor, according to the study, is genetic. On a low-carbohydrate diet, people with an inherited tendency toward higher LDL cholesterol appear to be especially sensitive to saturated fat, and they are the ones most likely to see their numbers climb.

“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, a registered dietitian and postdoctoral scholar at Stanford University School of Medicine, who presented the work.

Same diet, different results

Barad framed the findings as a corrective to the polarized way diet is often discussed. “These findings highlight that there is real heterogeneity in how people respond to diet,” she said. “Dietary conversations can sometimes become overly simplified. One person may say, ‘Low-carb diets always raise LDL cholesterol,’ while another says, ‘My LDL cholesterol did not change at all.’ Our findings suggest that both experiences can be true, depending, at least in part, on the individual’s genetic makeup.”

Healthy low-carbohydrate diets have been shown to help some people lose weight and improve blood sugar control. But their effects on LDL cholesterol, a key driver of heart disease risk, have been inconsistent. The researchers wanted a way to predict, in advance, who stands to benefit and who might be putting their cardiovascular health at risk.

Mining a landmark trial

The new work draws on DIETFITS, a randomized controlled trial at Stanford in which more than 600 adults followed either a healthy low-carb or a healthy low-fat diet for a year. The trial’s headline result, published earlier, was that neither diet outperformed the other for weight loss.

For the new analysis, Barad and colleagues focused on 431 DIETFITS participants for whom genetic data were available. They examined how each person’s genotype, saturated fat intake, and assigned diet related to changes in LDL cholesterol over the first six months.

Rather than looking at individual genes, the team used a polygenic score — a measure that combines the effects of thousands of genetic variants across the genome into a single estimate of a person’s overall tendency toward higher or lower LDL cholesterol. Most earlier work in this area has concentrated on single variants, which capture only a small slice of inherited risk.

Saturated fat as the trigger

Among participants on the low-carb diet, those with a higher genetic predisposition to elevated LDL were more likely to see their cholesterol rise. The analysis pointed to saturated fat as the driver: people at higher genetic risk showed the steepest LDL increases when they ate more saturated fat. Participants on the low-fat diet did not show the same pattern.

In other words, the genetic effect wasn’t simply that some people have higher cholesterol. It was that their cholesterol responded more strongly to a specific dietary input that tends to rise when carbohydrates fall.

Toward personalized advice

Barad suggested that, down the line, clinicians might use polygenic scores to flag patients who are more likely to experience an unfavorable LDL response to particular diets. Genetic testing of this kind isn’t routine in nutrition counseling today, but the approach points toward a more individualized way of matching people with eating patterns.

Even without a genetic test, she said, the study carries a practical lesson. Responses to diet vary, so people making a significant dietary change should monitor how their own bodies respond — through cholesterol checks, for example — rather than assuming they will follow the same trajectory as everyone else.

For those who choose to eat low-carb, the composition of the fat matters. General guidance recommends keeping saturated fat below 10 percent of daily calories and favoring unsaturated fats. Barad noted that leaning on sources such as nuts, seeds, olive oil, and avocado — rather than butter, beef tallow, fatty cuts of meat, and processed meats — may help reduce the risk of an adverse cholesterol response.

Preliminary, but pointed

The findings come with caveats. They were presented as a conference abstract and have not yet undergone the full peer review required for journal publication, so they should be considered preliminary. The researchers also note that further studies are needed to confirm the results and to establish whether they hold across diverse populations, since polygenic scores are often less accurate in groups underrepresented in genetic research.

Still, the work offers a plausible explanation for one of nutrition science’s most persistent contradictions. The question may not be whether low-carb diets raise cholesterol, but for whom — and the answer may be written, in part, in the genome.

DIETFITS was funded by the National Institute of Diabetes and Digestive and Kidney Diseases, the National Heart, Lung, and Blood Institute, and the Stanford Clinical and Translational Science Award through the National Institutes of Health. Barad was supported by an American Heart Association Postdoctoral Fellowship.

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Notes

1. Barad, A., et al. Polygenic risk, saturated fat intake, and LDL cholesterol response to low-carbohydrate and low-fat diets in the DIETFITS trial. Oral presentation, NUTRITION 2026, American Society for Nutrition, National Harbor, Md., July 27, 2026. (Conference abstract; not yet peer reviewed.)
2. Gardner, C. D., et al. “Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial.” JAMA 319, no. 7 (2018): 667–679.
3. American Society for Nutrition. “Is your diet driving up your cholesterol? That may depend on your genes.” News release via EurekAlert!, July 27, 2026. https://www.eurekalert.org/news-releases/1136476