Saturated Fat and Your Heart: New Norwegian Trial Challenges a Decades-Old Rule

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A Test of the Standard Advice

For decades, heart-health guidelines have told people to eat less saturated fat. This is the fat found in butter, cheese and red meat. In the United States, the advice is to keep it below about 10 percent of daily calories. Leading cardiology groups in the US and Europe also recommend replacing saturated fat with unsaturated fat. [3]

A new randomized trial from Norway, called CARBFUNC, deliberately went the other way. It was published on October 24 in the journal eBioMedicine. [1]

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What the Researchers Did

The study enrolled 193 adults with obesity in the Bergen area of western Norway. Participants were randomly assigned to one of three diets and followed for up to two years. [1]

One group ate a very-low-carbohydrate diet, with carbohydrates under 10 percent of energy, that was rich in fat. Close to a third of their calories came from saturated fat, more than double the usual recommendation. The other two groups ate diets closer to standard guidelines. [1][2]

According to the University of Bergen team, no earlier study had prescribed so much saturated fat for so long. [1]

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What They Found

LDL cholesterol rose by 5 to 10 percent in the high-fat, low-carbohydrate group. Many doctors treat LDL as the main warning sign for clogged arteries, so this result looks worrying at first. [1]

But the researchers found that the rise came mainly from larger LDL particles. They also reported favorable changes in several other cardiovascular risk markers. [1][2]

The key finding concerns apoB, a protein that sits on every cholesterol-carrying particle. Because each particle carries exactly one, apoB works as a rough count of particles that could contribute to artery plaque. In this trial, apoB did not rise in the high-fat group, and it did not change much differently from the two higher-carbohydrate diets. [1]

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Why LDL Alone May Not Be Enough

A standard cholesterol test measures how much cholesterol the LDL particles carry in total. It does not count the particles. ApoB testing is not part of a routine lipid panel, although it is becoming more common.

Researchers in the field have long suggested that LDL should be read alongside other values. Norwegian scientists have said that a raised LDL level is less likely to be a problem when triglycerides are low and "good" HDL cholesterol is high. [3]

The Bergen authors take a similar position. They argue that a higher LDL reading should not be treated as a risk factor on its own without looking at other markers. [1]

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What the Study Cannot Tell Us

The trial measured risk markers in the blood, not heart attacks, strokes or deaths. Whether this diet changes real-world outcomes remains unknown. [1]

The results also apply to a specific group: adults with obesity. Norwegian researchers have noted that high saturated fat intake can affect people with normal weight differently from people with obesity. [3] A small earlier Norwegian study found sharply higher LDL in healthy young women of normal weight after four weeks on a low-carbohydrate diet. [6] That study was tiny and short, and its authors urged caution.

Long diet trials are also hard to run. Participants must stick with a demanding eating plan for years, which makes clean results difficult to obtain.

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A Long-Running Scientific Dispute

The new trial adds to a wider argument. Earlier work from the same Bergen research environment, the FATFUNC trial, put men with abdominal obesity on either a very-high-fat or a high-carbohydrate diet. It found no significant LDL increase on the high-fat plan and no worse fat accumulation around organs. [4][5]

The evidence on the other side is also substantial. A 2024 review of meta-analyses in Frontiers in Public Health concluded that cutting saturated fat probably reduces combined cardiovascular events, with a risk ratio of 0.79. The same review found no clear effect on all-cause death or cardiovascular death, and it called for more high-quality long-term trials. [7][8]

In short, the science is less settled than public messaging often suggests, but it has not flipped.

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What This Means for Readers

This study is not a license to load up on butter and bacon. Its participants followed a strictly controlled plan, and the trial focused on minimally processed foods. Food quality matters as much as fat content: Norwegian researchers have stressed that what kind of food you eat may count as much as whether it is low in fat or in carbohydrates. [3]

Anyone with existing heart disease, high cholesterol or a family history of early heart problems should talk to a doctor before changing their diet. Asking about an apoB test may be a reasonable question to raise.

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Outlook

The Bergen team calls for further research into which people benefit from low-carbohydrate, high-fat eating and which should avoid it. [1]

The key test will be long-term studies that track actual heart attacks and deaths rather than blood markers. Until then, the CARBFUNC trial adds to the evidence that cholesterol numbers alone give an incomplete picture of heart risk.

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Sources

1. News-Medical (summary of University of Bergen release), "High intake of saturated fat can promote favorable changes in cardiovascular risk markers": https://www.news-medical.net/news/20261027/High-intake-of-saturated-fat-can-promote-favorable-changes-in-cardiovascular-risk-markers.aspx
2. UA.news, "In Norway, a diet high in saturated fat did not raise apoB": https://ua.news/en/health/u-norvegiyi-diieta-z-velikoiu-kilkistiu-nasichenikh-zhiriv-ne-pidvishchila-apob-news-medical
3. ScienceNorway (University of Bergen researchers), "Is food quality more important than fat and carbohydrate content?": https://sciencenorway.no/food-and-diet-food-choices-healthy-fats/eating-less-processed-foods-gave-weight-loss-and-lower-risk-of-heart-disease--also-among-men-on-a-high-fat-diet/1639343
4. FoodNavigator, "Fresh study suggests saturated fat could be good for you" (FATFUNC trial, American Journal of Clinical Nutrition): https://foodnavigator.com/Article/2016/12/05/Fresh-study-suggests-saturated-fat-could-be-good-for-you
5. People's Pharmacy, "How bad is it to eat saturated fat": https://peoplespharmacy.com/articles/how-bad-is-it-to-eat-saturated-fat
6. Tidsskrift for Den norske legeforening, "Lipid profile on a low-carb diet in healthy people": https://tidsskriftet.no/2013/06/originalartikkel/lipidprofil-ved-lavkarbokosthold-hos-friske
7. Aramburu et al., Frontiers in Public Health (2024), umbrella review on reducing saturated fat: https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2024.1396576/full
8. PubMed entry for the same review: https://pubmed.ncbi.nlm.nih.gov/38887252/

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