In a Norwegian Trial, a Very Low-Carb Diet Heavy in Saturated Fat Raised LDL but Not ApoB
Bergen researchers followed 193 adults with obesity for up to two years and found triglycerides fell and HDL rose, but they stress that risk markers are not heart attacks.
Outspoken Digest Nutrition Desk
Thursday, October 29, 2026/2 min read
A diet that put nearly a third of daily calories into saturated fat pushed LDL cholesterol up, but it did not raise apoB or add coronary artery calcium in a two-year randomised trial in Norway. The result, from a secondary analysis of the CARBFUNC trial, was reported on 27 October by the University of Bergen and News-Medical, and published in eBioMedicine, a Lancet-family journal.
It is a result with large caveats, and the researchers say so themselves. It measured risk markers, not heart attacks, in 193 adults with obesity, so it does not show that a high-saturated-fat diet is safe.
What did the CARBFUNC trial test?
Adults in the Bergen area were randomly assigned to one of three diets for up to two years. One was very low in carbohydrate, under 10 percent of energy, and high in total and saturated fat. The other two followed guideline-style, carbohydrate-based eating, with carbohydrate from either refined or minimally refined sources. Protein, added sugar (about 1 to 2 percent of energy) and vegetables (500 grams a day) were matched, and energy targets were about 2,500 kilocalories for men and 2,000 for women, according to the university's Norwegian press release.
Saturated fat supplied close to a third of energy on the high-fat diet, against the under-one-tenth limit that dietary guidelines usually recommend.
What happened to cholesterol and heart risk markers?
LDL cholesterol rose by about 5 to 10 percent on the high-fat diet, mainly because of larger LDL particles. Small, dense particles, which earlier research links to higher risk, did not change meaningfully. Triglycerides fell by roughly 20 to 35 percent and HDL cholesterol rose by about 5 to 18 percent. ApoB, a protein linked to cardiovascular risk, did not increase, and its change did not differ appreciably from the carbohydrate-based diets.
CT scans at the start and after 12 months showed no clear rise in coronary artery calcification on the high-fat diet, and no difference between groups. Cathrine Loddervik, the first author, said the findings show the value of looking at more than one risk factor, and Professor Simon Dankel said a rise in LDL should not be read on its own.
Why this does not settle the saturated fat debate
The limits are significant. It is a secondary analysis, since the trial's primary outcome was visceral fat, reported separately. Everyone had obesity, so the findings may not apply to other people. The high-fat arm also removed most grains, so the diets differed in more than fat. The authors say the LDL increase cannot necessarily be dismissed as unimportant and that long-term effects need more research. Surrogate markers can be reassuring and still miss real-world outcomes, and only a longer trial tracking heart attacks and deaths could answer that.
This article is reporting, not medical advice. Anyone with high cholesterol, diabetes or heart disease, or who is considering a very low-carbohydrate or otherwise restrictive diet, should decide with a clinician who knows their history.
The researchers say more long-term research is needed. Until trials track clinical outcomes, the cautious reading is that this trial complicates the single-number view of LDL, not that it overturns the guidance.
Published in The Outspoken Digest
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