The ketogenic diet is becoming increasingly popular. As a cardiologist, I have a built-in prejudice that it could not possibly be healthy as it is so high in saturated fat.

Yet, recently, I have seen more patients begin to lose weight after years of futile dieting. When I compliment them about this, only then will they tell me about their keto diet, expecting that I will not approve.

Is there any science behind this nutritional regimen that so many of my patients are following?

A ketogenic diet means bringing on the bacon. It involves eating high-fat, very low-carbohydrate foods, with most calories coming from fat. Instead of the body using carbs to get its energy, it turns to another source. It is forced to burn fat, producing a substance made in the liver called ketones, which go into the bloodstream so muscles can use them for fuel.

With this as background, I looked at some of the emails that I get almost daily (usually filtered into junk mail) about a product called Keto Burn, containing BHB (Beta-hydroxybutyrate). According to the website, BHB “is able to greatly speed up weight loss by putting your body into ketosis." It has been on TV’s Shark Tank, endorsed by Dr. Oz, and looks appealing. But, the studies behind it involve only a few healthy people taking the supplement and following a keto diet for a few weeks or months.

One obvious conclusion: Beware of dietary supplements claiming to be the secret to weight loss. This is true for both over-the-counter and prescription pills. Starting with the drug fen-phen, a prescription weight loss medication given 20 years ago until it was taken off the market because it damaged heart valves, taking drugs that promote weight loss is almost never the answer.

The keto diet itself, though, does not involve taking pills. It involves eating red meat, poultry, fish, dairy in the form of heavy cream and cheese, such vegetables as celery and cucumbers, nuts and seeds, and grains and fruits in order to produce a very low total-carb intake.

There is evidence that it results in weight loss. A meta-analysis of 13 randomized controlled trials suggested that people on this program lost more weight than those following low-fat diets. People reported less hunger, which may have to do with the satiating effects of fat and protein. Ketone bodies produced by the body may also reduce hunger.

Beyond weight loss, it has been used successfully in both children and adults to help manage insulin-dependent diabetes. In an article in the journal Pediatrics in June 2018, adults and children who followed a very low-carbohydrate diet were surveyed and had exceptional control of their sugars without risk of increased hypoglycemia. Much lower doses of insulin were required.

The ketogenic diet was originally developed in 1924 to help treat epilepsy. A recent study looked at 11 randomized trials involving a total of 778 patients with drug-resistant epilepsy. These studies suggest up to a 50 percent decrease in seizures, with participants experiencing a good deal of gastrointestinal symptoms and elevated cholesterol.

There are some significant downsides to this diet. Maintaining it is difficult, with almost complete carbohydrate restriction and high saturated fat intake leading to irritability, headaches, “brain fog,” bad breath, kidney stones, osteoporosis, and a higher risk of gout.

It is not a “do-it-yourself diet,” as careful medical advice is crucial to watch for decreasing needs for blood pressure and diabetic medication as weight loss occurs. Cholesterol levels and kidney function need to be carefully monitored. One study pointed out that this need for medical supervision is complicated by the fact that many people do not tell their doctor about their diet, as they are afraid of being scolded – the technical term is medically shamed -- even if doctors do not perceive that they are doing this.

There are no studies lasting more than one year suggesting its safety, and we do not know if the benefits outweigh the risks in the elderly and people with multiple health problems. Although this diet has been shown to lower triglyceride levels, it can raise LDL (bad) cholesterol levels, which could promote coronary artery disease.

Changing from all saturated fats to include more of the healthy polyunsaturated fats may be an attractive long-term option. One of the few long-term studies available, recently published in Lancet, suggests that low-carbohydrate diets favoring animal-derived proteins and fats were associated with a higher mortality risk, and the opposite was true for plant-based sources.

The bottom line: I was surprised at the quality of evidence suggesting the keto diet may have a beneficial role for some people. Like many other things in life, one kind of diet probably isn’t best for everyone. I will still continue to recommend the Mediterranean diet for most people, as the keto diet is not ideal for people with heart disease, the elderly, and people with certain serious medical issues.

The keto diet may be an alternative to weight loss drugs or bariatric surgery, and more studies are needed to see whether it is a safe long-term option for people with diabetes as well as the healthy obese. For now, if you try it, please use caution, let your doctor know, and work with appropriate medical professionals. And if you feel you are being medically shamed, you might gently point that out. You could be doing your doctor a favor.

David Becker, M.D., is a frequent Inquirer contributor and a board-certified cardiologist with Chestnut Hill Temple Cardiology in Flourtown, Pa. He has been in practice more than 25 years.