Emma Lawson
The keto community is having a genuinely uncomfortable week. A large observational study dropped June 4, 2026 in Scientific Reports, analyzing 43,776 American adults from NHANES data spanning 2001 to 2018, and found that people eating a ketogenic dietary pattern had a 24% lower risk of all-cause mortality (HR = 0.76, 95% CI 0.63-0.90, P = 0.003) with no corresponding spike in cardiovascular deaths. Good news, right? Except that five months earlier, a University of Utah Health team published findings in Science Advances showing that long-term keto caused fatty liver disease, wrecked lipid profiles, and seriously compromised insulin function in mice, with male subjects sustaining the worst liver damage. Both studies are real. Both matter. Neither one cancels the other out, and that’s exactly the problem.
What the NHANES Study Actually Measured (and What It Didn’t)
Observational data from NHANES is useful for spotting associations across large populations. It is not a randomized controlled trial. The 43,776 adults weren’t assigned to eat keto; researchers identified a “ketogenic dietary ratio” from self-reported food intake and tracked who lived and who didn’t over years of follow-up. That’s a meaningful signal, but it carries the standard caveats: people who eat lower-carb whole foods also tend to drink less soda, smoke less, and pay more attention to their health overall. Residual confounding is real.
Still, the cardiovascular mortality finding is worth sitting with. The fear that keto kills people through heart disease hasn’t shown up in this dataset, and this is a large, demographically diverse sample. The study doesn’t tell you what happens to your LDL at year three, or whether someone with familial hypercholesterolemia should be running this experiment on themselves. What it tells you is that across a wide population, a low-carbohydrate dietary pattern wasn’t associated with dying of cardiovascular disease at higher rates than everyone else.
The Utah Data Is More Specific, and More Alarming
The mouse research out of the University of Utah is a different kind of finding entirely. It’s mechanistic rather than epidemiological, which means it’s asking why rather than how many. And what the Utah team found is specific enough to warrant attention beyond the usual “but it was mice” dismissal.
After extended time on keto, when animals were reintroduced to even small amounts of carbohydrates, blood glucose spiked abnormally high and stayed elevated far longer than it should have. The researchers flagged compromised pancreatic insulin release as the likely mechanism. Combine that with the fatty liver findings and the lipid abnormalities, and you have a picture of an animal whose metabolic flexibility has been quietly eroded. It handled fat just fine; it could no longer handle carbohydrates at all.
This matters for humans because most people don’t stay on keto forever. They cycle on and off, they travel, they have holidays, they quit and restart. If long-term keto blunts your capacity to process glucose, those transitions aren’t neutral metabolic pauses; they might be the most dangerous periods.
Why the Contradiction Exists (and Won’t Be Resolved Quickly)
| Study | Type | Sample | Key Finding | Population |
|---|---|---|---|---|
| NHANES (June 2026, Scientific Reports) | Observational | 43,776 American adults | 24% lower all-cause mortality (HR = 0.76, 95% CI 0.63-0.90) | Diverse U.S. population, 2001-2018 |
| University of Utah (Jan 2026, Science Advances) | Mechanistic/Animal | Mice | Fatty liver, compromised glucose tolerance, impaired insulin response | Extended ketogenic diet exposure |
The r/ketoscience subreddit has been threading these two studies against each other in real time, and the honest answer is that they’re not as contradictory as they look. They’re measuring different things over different timeframes in different organisms. The NHANES analysis captures population-level mortality patterns in people who eat a certain way. The Utah study captures what happens physiologically inside a body running on near-zero carbohydrates for an extended stretch. Both can be true simultaneously.
What makes this genuinely hard is that cardiologists and dietitians are already split on keto for reasons that predate both studies. Keto reliably raises HDL cholesterol and lowers triglycerides; those are consistent findings. But LDL responses are all over the map. Some people see modest increases. Others, particularly those with certain genetic lipid profiles, see dramatic ones. Fat composition matters: a keto diet built around olive oil, fatty fish, and avocado behaves differently in the body than one built around bacon and cheese every day. There is no single “keto diet” in these studies, which means there’s no single answer about cardiovascular risk.
The Hybrid Protocol Gaining Traction in 2026
An April 2026 protocol paper in PMC proposed what its authors called an Adaptive Ketogenic-Mediterranean Protocol, essentially a structured cycling approach that pairs keto’s metabolic advantages with the Mediterranean diet’s better-studied long-term safety profile. The researchers estimated a ketogenic metabolic advantage of roughly 100 to 300 kcal per day over standard diets, and notably positioned the protocol as superior to GLP-1 drugs for countering the metabolic adaptation that follows significant weight loss.
That’s a bold claim, and it’s a protocol paper rather than a clinical trial, so the evidentiary bar is lower than it sounds. But the underlying logic is sound: using keto’s documented advantages for specific purposes, namely fat loss and metabolic flexibility, while avoiding the extended duration that the Utah data suggests may carry real costs. Cycling out of ketosis regularly, particularly into a Mediterranean-style eating pattern, could theoretically preserve the glucose tolerance that long-term continuous keto may compromise. This is hypothesis, not proven guidance. But it’s the kind of hypothesis worth watching in the next few years of research.
What This Means If You’re Actually Deciding Something
If you’re currently doing keto and your LDL is climbing, that’s not a number to hand-wave away with “HDL went up too.” Get a cardiovascular risk assessment from someone who can look at your full lipid panel, family history, and inflammatory markers together. That’s not alarmism; it’s how the decision should be made.
If you’re considering long-term keto as a permanent dietary identity rather than a tool with a timeframe, the Utah data should give you pause. Not because one mouse study settles anything, but because the mechanism it identifies, compromised insulin response after prolonged carbohydrate restriction, is plausible and currently under-studied in humans.
If you’ve been cycling in and out of keto for years without issues, the NHANES mortality data is genuinely reassuring on the cardiovascular front, with the caveat that population-level associations aren’t personal guarantees. No study grants individual exemptions.
The research on this will keep improving. Neither of these 2026 studies is the final word, and anyone telling you otherwise isn’t reading carefully enough.
Sources
- Ketogenic Diet and All-Cause Mortality, NHANES Analysis, Scientific Reports (June 4, 2026)
- University of Utah Health: Keto’s Hidden Long-Term Metabolic Cost, ScienceDaily (January 27, 2026)
- Adaptive Ketogenic-Mediterranean Protocol vs. GLP-1 Agonists, PMC (June 2026)
- Ketogenic Diet in 2026: New Insights and Guidance, El Paso Back Clinic (February 9, 2026)
Photo: Puwadon Sang-ngern via Pexels
This article is for general informational purposes only and does not constitute medical or dietary advice. Always consult a licensed healthcare provider or registered dietitian before making significant changes to your diet, especially if you have a medical condition.
