We all know the saying “You are what you eat.” But does that mean you’ll get smooth, perfectly oiled skin by dunking a tablespoon of butter in your morning coffee? Some proponents of the high-fat, very-low-carb ketogenic diet seem to think so — even if it means putting butter on top of their butter.

With the diet rising in popularity, more and more people are starting to ditch the bread and pasta in favor of adopting a keto diet food list replete in fat-laden foods, like meat, avocado, and nut butter. The quick weight loss many people experience on the diet has been a common motivation, but the effect of the diet on skin seems less certain. Some dieters report having a clearer and brighter complexion while on the diet, while many others encounter a strange, itchy red rash across their torsos.

So the question remains: Is the keto diet healthy for the skin?

What Is the Keto Diet and Why Is It So Popular?

The thinking behind keto, according to U.S. News & World Report, is to train your body to burn fat rather than carbohydrates with the intention of losing weight and increasing feelings of fullness. By adding more fats to your diet and eliminating carbohydrates, you’ll send your body into a natural metabolic state called ketosis, during which the body breaks down fats into ketones. Ketones then become the body’s main source of energy, rather than carbs or protein, theoretically leading to weight loss.

The keto diet began gaining popularity around 2013, says Franziska Spritzler, RD, CDE, who is based in Orange County, California. She credits the fad diet’s growth to books such as The Art and Science of Low Carbohydrate Living and The Art and Science of Low Carbohydrate Performance by Steve Phinney MD, PhD, and Jeff Volek, Phd, RD — two texts that lay out the potential health perks of going low-carb.

What Are the Proposed Benefits of the Keto Diet?

Although, according to previous research, the ketogenic diet was originally developed to help children control epilepsy, an article published in February 2018 in the journal Aging suggested increasing fat and lowering carb intake could be an effective tool for managing cancer, while another study found it to be effective at lowering blood sugar in people with type 2 diabetes. Still, experts aren’t in agreement on those results, and more research is needed.

For the time being, Abbey Sharp, RD, a blogger for Abbey’s Kitchen who is based in Toronto, Canada, points out weight loss is the most popular draw of the keto plan you hear about today. Still, she doesn’t recommend it to her clients due to its restrictive nature and potential for causing nutrient deficiencies. “When it comes to weight management, I don’t believe in taking on any super-restrictive diets that mean cutting out full food groups,” Sharp says. Spritzler, on the other hand, says she has anecdotally seen positive results from keto in her clients with type 2 diabetes and prediabetes.

Can You Expect Unpleasant or Harmful Keto Side Effects? And Is There a Wrong Way to Do Keto?

On these matters, Spritzler and Sharp agree.

For one, the reduction in carbs could lead you to consume too little fiber, says Sharp. This in turn could goof with your digestive system. “Constipation is very common on a keto diet — or any low-carb diet — because you’re cutting back on fiber-rich whole grains and fruit,” Sharp says. (Whole grains and fruit tend to contain more carbs than keto-friendly foods.) More seriously, the restrictive nature of keto could furthermore lead to disordered eating in some people; thus, it isn’t recommended for people who have a history of eating disorders.

Nutritionally speaking, keto may also be problematic. Spritzler says some people could interpret the fat-forward approach of keto as permission to eat as much processed food as they want — a choice that could affect their overall health, including that of the skin, she notes.

How Cutting Carbs May Affect Your Skin

Although it seems counter intuitive to eat more fats and fewer carbohydrates for clearer skin, to Jennifer Gordon, MD, a dermatologist in Austin, Texas, that’s exactly how keto may help improve your complexion — provided you’re cutting back on the right carbs and upping your intake of the right fats. By eliminating simple carbohydrates in particular, you’re targeting the body’s excess inflammation — which is a huge promoter of acne. “It’s usually simple carbohydrates that create inflammation,” she says. “When you lower inflammation in the body, you can see this in your skin as feeling more radiant, less red, and less congested.”

But following an anti-inflammatory diet may also be the cause of a side effect called prurigo pigmentosa — commonly referred to as “keto rash.” Sharp says this is “a rare form of inflammatory dermatosis” that often appears on people in the early stages of ketosis.

How Increasing Fat Intake May Affect Your Skin

Omega-3 fatty acids are great for both hair and skin, Dr. Gordon points out. “There are always people who worry that eating too much fat gives you acne,” she says. “This is actually untrue.” But again, that’s not license to go binge on junk food. Sharp and Spritzler agree that increasing healthy-fat intake (especially sources of omega-3s, such as salmon and walnuts) may help soothe dry, itchy, scaly skin. Sharp also adds that avoiding omega-6 fats, such as vegetable oils, has been associated with improvements in inflammatory acne.

Is Keto Good or Bad for the Skin?

The consensus from Spritzler, Sharp, and Gordon is that while the keto diet has the potential to clear up acne, this benefit isn’t guaranteed. After all, everyone’s skin is different.

For instance, Sharp notes that the freedom to eat dairy products (such as butter, cheese, and cream) on keto might be a problem for some. “Some people find dairy triggering for acne,” she says. “The association isn’t the same for everyone. So try to experiment to see if cutting back on dairy makes a difference in your skin.”

Gordon notes that “this isn’t a diet to do for your skin.” Instead of trying keto to make your skin glow, Gordon suggests making simpler lifestyle changes, such as making sure you’re drinking enough water, avoiding highly saturated “bad” fats (think butter, margarine, and fatty meats, such as pork), and cutting down on simple carbs (like white bread, white pasta, cookies, and cake).

Regardless of your intentions for going keto, be sure to consult your doctor before starting because the keto diet can pose dangers for certain people. Notably, while some people with type 2 diabetes may indeed benefit from the diet, keto isn’t for everyone. Its concentration on protein, for example, may negatively affect people with kidney damage. According to the Mayo Clinic, a dysfunctional kidney would have a hard time digesting protein compounds. Others who may want to avoid the ketogenic diet include expecting mothers, young children, and people on certain kinds of medication.

Ultimately, if you’re hoping to use keto to help clear your skin, talk to your doctor and dermatologist before trying it out to see if it’s safe for you.