Genes may determine whether a low-carb diet raises cholesterol – Earth.com
08-01-2026
Your genes may determine whether a low-carb diet raises cholesterol
ByRaquel Brandao
Earth.com staff writer
People respond differently to low-carb diets and this may depend partly on their genes, according to a new study
People carrying a genetic tendency toward high cholesterol levels saw the sharpest rises, while others on the same plan saw no changes in their levels
The result helps explain a long-running argument, in which two people follow the same rules and get opposite blood results
It also raises the prospect of knowing in advance who should be careful when replacing carbohydrates with fats while on a particular diet
Same diet, different cholesterol
The analysis comes from Alexa Barad, Ph.D., R.D.N., a postdoctoral scholar at the Stanford University School of Medicine (Stanford Medicine)
LDL cholesterol is the kind that collects inside artery walls and narrows them over decades. Doctors treat it as one of the clearest measurable warning signs of heart disease
Low-carb eating has a mixed record on that number. Some people watch it climb steeply within months. Others see no change at all
“Our findings suggest that a person’s LDL cholesterol can respond very differently to the same dietary pattern. While some people may experience little change in LDL cholesterol, others may experience large increases,” Dr. Barad stated in response to questions from Earth.com
Body size and genetics play a role
Body size explains part of the split. One analysis pooled 41 randomized trials of carbohydrate restriction
In trials of lean participants, LDL rose by roughly 40 mg/dL. In trials of participants with obesity, it held steady or fell
Genetics appears to explain another part. Dr. Barad said dietary conversations often get flattened into slogans
One person is certain that low-carb diets always raise cholesterol, and another is certain that theirs never budged
“Our findings suggest that both experiences can be true, depending, at least in part, on the individual’s genetic makeup,” said Dr. Barad
A second look at genetic data
The data comes from DIETFITS, a Stanford trial that ran for a year. More than 600 adults were assigned either a healthy low-carb or a healthy low-fat diet
Neither diet won. Average weight loss landed in the same place for both groups. Individual results ranged from dramatic loss to modest gain
That trial had a genetic question built into it. Participants were screened for a small set of variants thought to mark them as low-fat or low-carb responders
The pattern predicted nothing about who lost weight, and enthusiasm for matching diets to genotypes cooled
Dr. Barad’s team went back to the same participants with a much wider genetic net. They analyzed 431 people whose genetic data was on file
LDL cholesterol was tracked from the start of the diet trial through six months, alongside how much saturated fat each person was eating
Diet was measured through unannounced interviews covering everything a participant had eaten the previous day
Saturated fat is the trigger
Among people on the low-carb diet, those with a genetic predisposition toward high LDL were the ones whose cholesterol climbed
The route ran through fat. The higher a person’s genetic risk, the more their LDL rose as their saturated fat intake went up. Participants on the low-fat diet showed no such pattern
Diet assignment is relevant because cutting carbohydrates leaves a gap, and butter, cheese and meat often fill it
Even in a trial designed around healthy eating, the low-carb group averaged roughly 15 percent of calories from saturated fat. Dietary guidelines suggest staying under 10 percent
“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,” Dr. Barad told Earth.com
Thousands of variants, one number
Earlier attempts to find the genetic side of this mostly hunted single variants, one gene at a time. That approach kept coming up short
Dr. Barad’s team used a polygenic score instead
Thousands of variants scattered across the genome each nudge cholesterol slightly up or down. Adding them together yields one number that describes a person’s overall tendency
This is not the rare inherited disorder that leaves some families with dangerous cholesterol from childhood. It is a common variation, spread thinly, of a kind that almost everyone carries to some extent
The same pattern has surfaced outside a clinical trial
A separate study compared people eating low-carb, high-fat diets against people eating a standard one. Only those with a high genetic score for LDL had markedly higher cholesterol
One important limitation remains. These genetic scores were developed primarily using data from people of European ancestry, making them less accurate for individuals from other populations
What to do without a test
Polygenic scores are not part of routine cholesterol care, and Dr. Barad is not telling anyone to wait for them
The usable lesson is to check instead of assume. A blood test before a dietary change, and another a few months later, beats any general rule about low-carb eating
Fat cutting carbohydrates can lean on nuts, seeds, olive oil and avocado
Those choices displace butter, beef tallow, fatty cuts of meat and processed meats
The findings remain preliminary. Conference abstracts are screened by a committee of experts, but they have not been through journal peer review
Your genes may hold the answer
Until now, no one had shown that a genome-wide cholesterol score predicts who reacts badly to cutting carbs
The same trial that found no genetic signal for weight loss contains a clear one for cholesterol
Precision nutrition has promised tailored eating advice for two decades and delivered little that a clinic can act on. A score that flags who should skip the butter on a low-carb diet would be a concrete start
For now, the findings point to the person, not the diet. Two people can follow the same low-carb plan and walk away with opposite cholesterol results
Part of the explanation is written in their genes
Dr. Barad presented the findings at the annual meeting of the American Society for Nutrition (ASN)
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