Researchers reviewed cases where people following a ketogenic (keto) diet experienced very high cholesterol levels that could harm their health. The keto diet is popular for weight loss because it focuses on fats and proteins while cutting carbs, but this review found that some people’s cholesterol levels became dangerously elevated. The study examined different cases to understand why this happens and who might be at higher risk. This information helps doctors and patients understand potential risks before starting a keto diet, especially for people with existing cholesterol problems.

The Quick Take

  • What they studied: Whether the ketogenic diet can cause unhealthy cholesterol levels in some people
  • Who participated: This was a review of published case studies and reports of people who developed very high cholesterol while on a keto diet. No new patients were studied directly.
  • Key finding: Some people following a keto diet developed severely elevated cholesterol levels, which could increase their risk of heart disease
  • What it means for you: If you’re considering a keto diet, especially if you already have cholesterol problems or family history of heart disease, talk to your doctor first. Regular cholesterol checks are important if you do try this diet.

The Research Details

This was a review study, meaning researchers looked at existing case reports and studies rather than conducting new experiments. They examined documented cases where people on ketogenic diets developed severe dyslipidemia—a medical term for very high levels of fats in the blood, particularly cholesterol and triglycerides.

The researchers analyzed these cases to identify patterns: who was affected, what cholesterol numbers they reached, how quickly the changes happened, and what happened when people stopped the diet or made changes. By reviewing multiple cases together, they could spot common themes and risk factors.

This type of review is useful for identifying potential problems with popular diets, but it doesn’t prove the diet causes the problem in everyone—it just shows it can happen in some people.

Understanding which people might have dangerous reactions to the keto diet helps doctors give better advice. Since the keto diet is very popular for weight loss, knowing about potential cholesterol risks is important for public health. This review helps identify warning signs and who needs extra monitoring.

This is a review of existing cases rather than a controlled study, so it shows what can happen but doesn’t tell us how often it happens or prove direct cause-and-effect. The findings are based on reported cases, which may not represent all people trying keto. For stronger evidence, we’d need studies that track many people on the diet over time and measure their cholesterol regularly.

What the Results Show

The review found that some people on ketogenic diets developed very high cholesterol and triglyceride levels—sometimes reaching dangerous levels that significantly increase heart disease risk. These elevated levels appeared in people who had been following the diet for varying lengths of time.

The cases showed that the high-fat nature of the keto diet can push cholesterol levels up in certain individuals. This was particularly concerning because some people didn’t realize their cholesterol was climbing since they weren’t getting regular blood tests.

When people stopped the keto diet or modified it, their cholesterol levels typically improved, suggesting the diet was the main factor causing the problem. However, the improvement didn’t happen instantly—it took weeks to months for cholesterol to return to normal levels.

The review identified that certain people appeared more vulnerable to severe cholesterol increases on keto, including those with family history of high cholesterol, existing cholesterol problems, or certain genetic conditions. Age and overall health status also seemed to play a role in who experienced the most dramatic increases.

Previous research has shown that keto diets can raise cholesterol in some people, but this review highlights that the increases can be severe enough to cause real health concerns. Most nutrition experts already knew keto could affect cholesterol, but this review emphasizes that the effect can be more dramatic than many people expect.

This review only looked at cases where problems occurred—it doesn’t tell us what percentage of keto dieters experience this issue. We don’t know how many people do keto without developing high cholesterol. The cases reviewed may not represent all possible outcomes, and some cases might have had other factors contributing to high cholesterol. The review doesn’t provide detailed information about diet quality, exercise, or other lifestyle factors that could affect results.

The Bottom Line

If you want to try a keto diet: (1) Get your cholesterol checked before starting, (2) Have it checked again after 4-6 weeks, (3) Tell your doctor you’re doing keto, (4) Consider working with a dietitian to make the healthiest version of the diet, (5) Stop or modify the diet if cholesterol becomes very high. These recommendations are based on case evidence showing potential risks.

This research matters most for people with: existing high cholesterol, family history of heart disease, genetic cholesterol disorders, or those over 40. People with no cholesterol concerns may have lower risk, but everyone should monitor their cholesterol if trying keto. Discuss with your doctor before starting, especially if you take cholesterol medications.

Cholesterol changes on keto can appear within weeks. If problems develop, they usually show up within the first 1-3 months. If you stop the diet, cholesterol typically improves over 4-12 weeks.

Want to Apply This Research?

  • Track your cholesterol levels (total, LDL, HDL, and triglycerides) every 4-6 weeks if following keto. Log the specific numbers and note any diet changes to see patterns.
  • If using a nutrition app while on keto, add a reminder to schedule cholesterol blood tests at regular intervals. Set alerts to review your cholesterol results and compare them to baseline numbers.
  • Create a simple chart in your app showing cholesterol trends over time. Include dates of blood tests, cholesterol numbers, and any diet modifications. Share this with your doctor to make informed decisions about continuing the diet.

This review discusses potential risks associated with ketogenic diets based on case reports. It does not apply to all people following keto, and individual responses vary significantly. Before starting a ketogenic diet, especially if you have existing cholesterol problems, heart disease, or take medications, consult with your healthcare provider or registered dietitian. Regular cholesterol monitoring is recommended if you choose to follow this diet. This information is educational and should not replace professional medical advice.