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Why does keto raise LDL cholesterol in some people?

Keto and Cholesterol: Why LDL Rises in Some People

Reviewed · 8 sources · By Anthony Falcone

The short answer: On average, keto and other low-carb diets raise LDL cholesterol a little, while triglycerides fall and HDL rises. The average hides big differences: in trials where people were of normal weight, LDL rose by about 41 mg/dL, while in trials of people with obesity it didn't rise at all. So test your lipids before and after you start, and talk to your doctor if LDL climbs a lot.2,3,1

Before you start

  • If you have familial hypercholesterolaemia, very high cholesterol, heart disease, or have had a heart attack or stroke, talk to your doctor before you start keto. LDL raises heart risk with its level and how long it stays high, so a rise matters more when your risk is already high.6
  • If you take medicine for cholesterol, blood sugar or blood pressure, talk to your doctor first, and never stop or change a prescribed medicine on your own because of a diet.
  • This guide is for healthy adults. Children, teenagers and pregnancy are outside it; ask your doctor.
  • 41 mg/dL average LDL rise on low-carb diets in trials where people were of normal weight (BMI under 25)1
  • 44% rise in LDL versus controls after 3 weeks of strict low-carb, high-fat eating in lean young adults7
  • 5–107% the range of individual LDL rises in that same 3-week trial7
  • 0.12 mmol/L average LDL rise versus low-fat diets in 13 trials of 12 months or longer2
  • 17% fewer cardiovascular events when people cut saturated fat for at least 2 years (general diets, not keto)5

Does keto raise cholesterol?

A little, on average. A meta-analysis of 13 randomised trials lasting 12 months or more compared ketogenic diets (no more than 50 g of carbohydrate a day) with low-fat diets. LDL cholesterol was 0.12 mmol/L higher on keto, but triglycerides were 0.18 mmol/L lower and HDL cholesterol 0.09 mmol/L higher.2

A second meta-analysis of 11 trials in 1,369 previously healthy adults, each lasting at least 6 months, found the same pattern for low-carb diets: more weight lost (2.17 kg) and lower triglycerides, but HDL 0.14 mmol/L higher and LDL 0.16 mmol/L higher. Its authors conclude that the benefits have to be weighed against the possible harm of higher LDL.3

A note on units: Europe reports cholesterol in mmol/L and the US in mg/dL. We give each number in the unit its study used. For scale, 20–40 mg/dL equals 0.5–1.0 mmol/L.6

Why LDL rises a lot in some people: body weight

The average rise is small because most diet trials enrol people with overweight or obesity. A 2024 meta-analysis of 41 randomised trials (1,379 people, about 19 weeks on average) found that body weight explained much of the difference. In trials where people's average BMI was under 25, LDL rose by 41 mg/dL on a low-carb diet; at a BMI of 25 to under 35 it didn't change; at 35 or more it fell by 7 mg/dL.1

Put another way, across trials, each unit lower in average starting BMI went with an LDL rise about 2.5 mg/dL bigger. In the same analysis, the amount of saturated fat people ate was not significantly linked to how much their LDL changed.1

A smaller meta-analysis of 3 trials in normal-weight adults points the same way: a ketogenic diet raised LDL by 1.08 mmol/L, total cholesterol by 1.47 mmol/L and apoB by 0.35 g/L compared with control diets, while also raising HDL.4

It can happen fast. In a Norwegian trial, 30 healthy, normal-weight young adults either ate under 20 g of carbohydrate a day for three weeks or kept their usual diet. On the low-carb diet, LDL went from 2.2 to 3.1 mmol/L on average, 44% more than in the control group, and apoB rose too. Individual rises ranged from 5% to 107%.7

Lean mass hyper-responders

"Lean mass hyper-responder" is a name for a pattern seen in some lean people on low-carb diets: LDL of 200 mg/dL or more together with HDL of 80 mg/dL or more and triglycerides of 70 mg/dL or less. It comes from a web survey of 548 adults on low-carb diets, not from a trial.8

In that survey, average LDL went from 145 mg/dL before the diet to 236 mg/dL on it. The leanest people with the best triglyceride-to-HDL ratios saw a median rise of 135 mg/dL, against 35 mg/dL for the heaviest with the worst ratios. 100 people (18%) fitted the hyper-responder pattern, and before the diet their LDL was much like everyone else's.8

The survey was advertised on social media, its respondents were leaner than average Americans, and they already knew how their LDL had changed, so it shows a pattern, not how common it is. The authors themselves write that the study should not be read as showing that this pattern is safe for the heart.8

Does a big LDL rise matter if HDL and triglycerides look good?

LDL is not just a marker. A consensus statement from the European Atherosclerosis Society, drawing on meta-analyses of more than 200 studies with more than 2 million people, concludes that LDL causes atherosclerotic heart disease, and that the risk grows with how high LDL is and with how many years it stays high.6

Researchers who study low-carb diets point out that the usual high-risk pattern is high triglycerides with low HDL, the opposite of what lean low-carb eaters tend to show. But they also say their data can't rule out a higher risk of heart disease, especially when LDL rises a lot, and that this needs studies that follow people over time.8,1

No trial in this guide measured heart attacks or strokes on keto; they all measured blood lipids. The honest answer is that nobody knows yet whether a large LDL rise on keto carries the same risk as high LDL for other reasons, so a big rise is a reason to see your doctor, not to ignore it.1,6

LDL, apoB and which tests to ask for

A standard lipid test reports LDL cholesterol: how much cholesterol the LDL particles carry. Each LDL particle carries one apoB molecule, so apoB counts the particles. Usually the two move together, but in metabolic syndrome, diabetes or high triglycerides they can drift apart, and apoB may then reflect the risk better.6

On keto, apoB rose along with LDL in both the 3-week trial and the meta-analysis of normal-weight adults, so this isn't only a change in how much cholesterol each particle carries.7,4

Because LDL rose within three weeks in the Norwegian trial, a test taken a few weeks into the diet already shows its effect. Get a baseline lipid test (LDL, HDL, triglycerides, and apoB if your doctor offers it) before you start, so you have something to compare against.7,6

What you can change if your LDL rises

Cutting saturated fat is one lever. A Cochrane review of 15 randomised trials (56,675 people) found that cutting saturated fat for at least two years lowered combined cardiovascular events by 17% (pooled from 12 of the trials, 53,758 people). Polyunsaturated fat and carbohydrate both looked like useful replacements; the effect of monounsaturated fat was unclear. These were general diets, not keto.5

On low-carb diets specifically, the 2024 meta-analysis found no significant link between the amount of saturated fat and the LDL change across trials. That doesn't prove fat type is irrelevant for an individual, but it means swapping fats may not fix a large rise in a lean person.1

Adding some carbohydrate back is the other lever. In a case series of 5 patients whose LDL had risen to 239–665 mg/dL on under 25 g of carbohydrate a day, moving to 50–100 g a day from fruit or starchy vegetables, under a doctor's supervision, lowered LDL in all five, by 100 to 480 mg/dL. Five patients is a very small and uncontrolled sample.8

What to do with this

  • Get a lipid test (LDL, HDL, triglycerides, and apoB if available) before you start keto and again a few weeks in.7,6
  • If you're lean (BMI under 25), expect a bigger LDL rise than the averages suggest, and check sooner rather than later.1,4
  • Don't let better HDL and triglycerides talk you out of a high LDL result: LDL raises heart risk with its level and its duration.6,8
  • If LDL rises a lot, talk to your doctor. Diet levers to discuss: replacing some saturated fat with polyunsaturated fat, or moving to a moderate low-carb intake of 50–100 g of carbohydrate a day.5,8

How sure is this?

  • Most trials are short: the 2024 meta-analysis averaged about 19 weeks, the Norwegian trial lasted 3 weeks with 30 people, and the normal-weight meta-analysis pooled only 3 studies. None measured heart attacks or strokes.1,7,4
  • The hyper-responder pattern comes from a self-selected web survey and a case series of 5 patients, the weakest kinds of evidence. Its data were self-reported and diet wasn't measured in detail.8
  • Industry and other ties: authors of the 2022 survey paper declared royalties from books recommending carbohydrate-modified diets, a low-carb cookbook (royalties donated), and membership income for low-carb research; four of them also wrote the 2024 meta-analysis, whose own declaration we couldn't read. The European Atherosclerosis Society panel's meetings were funded by unrestricted grants from MSD and Amgen, and most panel members declare ties to companies that make cholesterol-lowering drugs.8,1,6
  • The saturated-fat evidence comes from general diets over at least two years, not from keto. On low-carb diets, the amount of saturated fat didn't predict the LDL change.5,1
  • For six sources (Soto-Mota 2024, Bueno 2013, Mansoor 2016, Joo 2023, Retterstøl 2018, Hooper 2020) we could read only the abstract, so we use only the main results reported there.1,2,3,4,7,5

Common questions

Does keto raise cholesterol?

On average, slightly: LDL was 0.12–0.16 mmol/L higher than on low-fat diets in trials of 6 months or more, while triglycerides fell and HDL rose. Lean people often see much bigger rises.2,3,1

Why is my LDL so high on keto?

Body weight is the strongest known predictor: in trials where people's average BMI was under 25, LDL rose by 41 mg/dL on low-carb diets, but it didn't rise in people with obesity. Individual rises vary widely, from 5% to 107% in one trial.1,7

What is a lean mass hyper-responder?

A lean person on a low-carb diet with LDL of 200 mg/dL or more, HDL of 80 mg/dL or more and triglycerides of 70 mg/dL or less. The term comes from a web survey, and its authors say it shouldn't be read as proof that the pattern is safe.8

Is high LDL on keto dangerous?

Nobody knows for sure, because no trial has measured heart attacks or strokes on keto. LDL causes heart disease in proportion to how high it is and for how long, so a large rise is a reason to see your doctor.6,1

How do I lower LDL on keto?

Talk to your doctor first. Cutting saturated fat lowered cardiovascular events in general diets, with polyunsaturated fat or carbohydrate as useful replacements, and in a small case series, adding 50–100 g of carbohydrate a day back lowered LDL in all 5 patients.5,8

Should I test apoB on keto?

It helps. ApoB counts LDL particles, and it rose along with LDL on keto in trials. Test before you start and a few weeks in.6,7,4

Sources

  1. Soto-Mota A, Flores-Jurado Y, Norwitz NG, Feldman D, Pereira MA, Danaei G, Ludwig DS. Increased low-density lipoprotein cholesterol on a low-carbohydrate diet in adults with normal but not high body weight: A meta-analysis. American Journal of Clinical Nutrition, 2024. Meta-analysis. doi.org/10.1016/j.ajcnut.2024.01.009
  2. Bueno NB, de Melo IS, de Oliveira SL, da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. British Journal of Nutrition, 2013. Meta-analysis. doi.org/10.1017/S0007114513000548
  3. Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials. British Journal of Nutrition, 2016. Meta-analysis. doi.org/10.1017/S0007114515004699
  4. Joo M, Moon S, Lee YS, Kim MG. Effects of very low-carbohydrate ketogenic diets on lipid profiles in normal-weight (body mass index < 25 kg/m2) adults: a meta-analysis. Nutrition Reviews, 2023. Meta-analysis. doi.org/10.1093/nutrit/nuad017
  5. Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database of Systematic Reviews, 2020. Meta-analysis. doi.org/10.1002/14651858.CD011737.pub3
  6. Ference BA, Ginsberg HN, Graham I, et al. Low-density lipoproteins cause atherosclerotic cardiovascular disease. 1. Evidence from genetic, epidemiologic, and clinical studies. A consensus statement from the European Atherosclerosis Society Consensus Panel. European Heart Journal, 2017. Position stand. doi.org/10.1093/eurheartj/ehx144
  7. Retterstøl K, Svendsen M, Narverud I, Holven KB. Effect of low carbohydrate high fat diet on LDL cholesterol and gene expression in normal-weight, young adults: A randomized controlled study. Atherosclerosis, 2018. Randomised trial. doi.org/10.1016/j.atherosclerosis.2018.10.013
  8. Norwitz NG, Feldman D, Soto-Mota A, Kalayjian T, Ludwig DS. Elevated LDL Cholesterol with a Carbohydrate-Restricted Diet: Evidence for a "Lean Mass Hyper-Responder" Phenotype. Current Developments in Nutrition, 2022. Survey / forum study. doi.org/10.1093/cdn/nzab144

The Keto Blueprint is the step-by-step version of keto: a 14-day plan to start safely, with your macros, what to eat, how to handle the keto flu, which blood tests to get before you begin, and what to do if your cholesterol rises. 33 sources cited. If you'd rather not do keto, the Fat Loss Protocol is the non-keto path: your calorie, protein and weekly-loss targets and a plate that keeps you full. The Keto Blueprint · Fat Loss Protocol

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