Whether a low-carb diet drives up your LDL cholesterol may come down to your genes, according to research presented July 27 at NUTRITION 2026, the annual meeting of the American Society for Nutrition in National Harbor, Maryland. Alexa Barad, PhD, RDN, a postdoctoral scholar at Stanford University School of Medicine, reanalyzed 431 participants from the DIETFITS trial and found that low-carb dieters with a genetic tendency toward high LDL were the ones whose cholesterol climbed, and that the rise tracked with how much saturated fat they ate.
Key takeaways
- Among low-carb dieters, people with a higher genetic score for elevated LDL were more likely to see their cholesterol rise.
- The pattern was driven by saturated fat sensitivity. People at higher genetic risk had the largest LDL increases when they ate more saturated fat.
- People on the low-fat diet showed no such pattern.
What the study found
DIETFITS was a randomized controlled trial in which more than 600 adults followed either a healthy low-carb or a healthy low-fat diet for a year. According to the release from the American Society for Nutrition, the original trial found that neither diet beat the other for weight loss.
For this new analysis, Barad’s team looked at the 431 DIETFITS participants who had genetic data available and examined how genotype, saturated fat intake and diet type related to the change in LDL cholesterol from baseline to 6 months.
Most earlier work on diet and cholesterol genetics chased single gene variants. This team instead combined thousands of variants across the genome into a polygenic score, a single number estimating each person’s overall tendency toward higher or lower LDL.
In the low-carb arm, that score mattered. Participants who scored higher were more likely to see LDL rise, and the effect ran through saturated fat. In the low-fat arm, the same analysis turned up nothing.
“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,” Barad said in the release.
Dr. Kumar’s take
This is the first credible mechanistic explanation I have seen for something low-carb communities have argued about for years: the so-called lean mass hyper-responder, the lean, metabolically healthy person who goes keto and watches LDL double while everyone around them sees no change.
For years that argument has been stuck in a loop. One camp points to the outliers and says low-carb wrecks your lipids. The other camp says look at the group averages, nothing happens. Barad’s data suggest both camps were describing real people. Barad put it directly in the release, saying that both experiences can be true, depending at least in part on the person’s genetic makeup.
That reframes the question. It is not whether a low-carb diet raises LDL. It is in whom, and how much saturated fat it takes to do it.
Two caveats matter. First, this was presented at a conference and has not been peer reviewed, which the American Society for Nutrition states plainly. Conference abstracts get revised, and sometimes they do not survive review. Second, and this is the part I want you to hold onto clinically: a polygenic score is not a test you can order at your next visit. Your doctor cannot check this box on a lab requisition. Barad frames polygenic scores as a future tool, and I agree that is the right tense.
So the finding is important, but it does not yet change what you can actually do in an exam room.
What it means for you
What you can do is stop treating any diet as cardioprotective by default, including one that is working beautifully for your weight and blood sugar.
If you make a major dietary shift, low-carb or otherwise, get a lipid panel before you start and another one 8 to 12 weeks in. That window is long enough for LDL to settle at its new level and short enough that you are not carrying a problem for a year without knowing. If your LDL jumps meaningfully, that is your own genome answering the question, and it is a far better answer than any group average or online debate can give you. That same logic applies to the best diet to protect your heart: the pattern that helps most people is not automatically the pattern that helps you.
If you do stay low-carb, the fat sources are worth attention. Standard guidance is to keep saturated fat under 10% of daily calories. Barad suggested leaning on nuts, seeds, olive oil and avocado rather than butter, beef tallow, fatty cuts of meat and processed meats, which is also roughly the fat profile behind the Mediterranean pattern.
Measure, do not assume.