What Happens to Your Cholesterol When You Go on a Keto Diet?

For every person who talks up the ketogenic diet, there’s another person warning about its ill effects on your heart. The worry is that a very high-fat, moderate-protein, and very low carbohydrate diet will create a subsequent spike in cholesterol levels, which could, in turn, raise your risk for heart disease.

(The point of keto is to shift your body from a carb-burning state to a fat-burning one, which is called ketosis.)

But the effect of keto on heart health isn’t as straightforward as it sounds. Indeed, the keto diet may not have as detrimental an effect on your cholesterol as previously thought.

“When you review the data, a couple things are clear. Looking at population studies and clinical trials, the impact the keto diet has on lipids is modest,” says Daniel Soffer, MD, an internist and lipidologist at Penn Medicine in Philadelphia. Dr. Soffer is a member of the National Lipid Association, an organization dedicated to managing lipid problems.

Whether cholesterol numbers — particularly high-density lipoprotein (HDL) — go up or down largely depends on the quality of your keto diet. “One problem is that there’s not a single ketogenic diet. There are different ways to follow it, and some people are careful about the types of fats they eat, while others are not,” says Soffer.

Predicting How Keto May Affect Your Cholesterol Levels

Normal levels are less than 150 milligrams per deciliter (mg/dL). “About a quarter of the population has triglyceride levels above 150 mg/dL, which is the threshold to consider elevated triglycerides. This is a large percentage of the population, so it’s not uncommon,” says Soffer.

If you have normal levels, keto is likely safe to try. “For people with normal or perfect triglyceride levels, the impact from keto is minimal or none,” says Soffer.

If you have insulin resistance, type 2 diabetes, abdominal obesity, or your triglycerides are elevated — it may seem like you should shy away from keto, but the opposite may be true, Soffer argues, explaining that the low-carb nature of keto has the potential to decrease insulin resistance and improve triglycerides.

Flip that script, and “anything that reduces triglycerides will also [tend to] increase HDL,” says Soffer. Remember, HDL is a type of “good” cholesterol that ferries some LDL out of the bloodstream and into the liver where it can be metabolized and discarded, per the AHA — so increasing HDL is ultimately good for your heart.

How Keto May Change Your LDL Cholesterol

The bottom line is that keto alone may not contribute to the cholesterol spike that some people report when starting the diet. But if you start eating more saturated fat because you’re on keto, then your LDL will likely rise. An increase in saturated fat intake “has been shown over and over again” to increase LDL, Soffer says.

Keto May Harm People With a Genetic Mutation That Affects LDL Regulation

This is not something to tease out on your own. Instead, it’s just another reason why you should talk to your doctor about a dietary change, particularly if you have other health conditions, like high cholesterol.

The average person likely won’t notice anything amiss about their cholesterol, but “for someone with this genetic predisposition, [the keto diet] can be a hazardous diet,” says Soffer. In the short term, a small, six-month spike in cholesterol isn’t harmful — it takes a decade or more of high LDL to cause damage, he says — but if this is a rest-of-your-life way of eating, it can be dangerous. If a person has extremely high LDL levels, even in the short term, this warrants a visit to the doctor for evaluation, especially in people with a known cardiovascular risk.

If You Have High Cholesterol, Should You Avoid Keto?

High cholesterol doesn’t automatically disqualify you from keto. “We’re seeing really good cardiovascular results from a keto diet,” says Susan Ryskamp, RDN, a clinical dietitian at Michigan Medicine’s Frankel Cardiovascular Center in Ann Arbor.

Doctors will want to look at the overall picture with the goal of improving biomarkers like triglycerides, A1C, blood pressure, and body mass index (BMI). “On keto, if patients lose weight, get their BMI closer to, if not under, 30 (the threshold for obesity), and these biomarkers improve, we feel they’re at less of a cardiovascular risk,” says Ryskamp.

If a patient has severely elevated triglyceride levels — upwards of 1,000 mg/dL (recall that under 150 is normal) — then Ryskamp would likely suggest another diet first. But a triglyceride level of 300 may still be a go, with close monitoring and frequent lipid checks. “Most of the patients I see can safely go on keto,” she says.

How to Follow Keto in a Heart-Healthy Way

One of the draws of a keto diet is the idea that you can eat any and all fat that you want. That’s not a healthy mindset to step into. “I recommend patients choose cardioprotective [unsaturated] fats, like nuts, nut butter, seeds, avocado, and extra-virgin oils,” such as olive oil, says Ryskamp. Similarly, avoid foods that are high in saturated fat (like butter) as your primary fat sources.

It’s not just fats that are important, but maximizing the small amount of carbohydrates you’re allowed. Getting enough fiber can be a challenge, and you’ll want to make sure you’re eating plenty of low GI-index veggies (nonstarchy choices such as spinach and broccoli). Ultimately, the benefits come from replacing foods that experts believe are detrimental to overall wellness, such as processed carbs, with those that are heart-healthy, like unsaturated fats, she says.

It’s been repeated over and over: If you’re drastically changing your diet — which includes going keto — you need to talk to your doctor first and make sure it’s safe for you and your individual health concerns. You also want to get your lipids checked before and during keto, so your doctor can watch for a cholesterol spike and determine if this is a healthy diet for you.

Because keto is highly restrictive, most people don’t stay on it for the long haul, so watch your diet and plan appropriately when you go off the diet.

The Takeaway

• The ketogenic diet remains a topic of interest amid concerns about its impact on heart health and cholesterol levels.
• While studies suggest that a keto diet may have moderate benefits for levels of triglycerides and HDL (“good”) cholesterol, fluctuations in LDL (“bad”) cholesterol depend on diet quality and genetic factors.
• Talk to your doctor first if you’re considering adopting a keto plan, and incorporate only heart-healthy fats into your diet.