This week a new study by a well-respected cardiologist in Denver found that not only are ketogenic diets bad for long-term heart health, but they are not sustainable for lifelong weight loss. The study looked at the effects of keto dieting and found that too few of those who start a keto diet stay on it long enough to even measure the long-term health effects, so the short term benefit of quick weight loss is outweighed by the eventual weight rebound where people gain back all the weight and more and have higher cholesterol in the bargain.

"While the limited study of the keto diet shows those who follow it lose weight initially, it tends not to be sustainable according to 12-month data," according to Dr. Andrew Freeman, the study's author and director of cardiovascular prevention and wellness at National Jewish Health in Denver. " It is also unclear whether the weight loss is caused by achieving ketosis or simply by calorie restriction." That's possible since subjects followed in a keto versus low-fat high carb diet were shown to eat less on a keto diet, so it's not the keto part that helped them lose weight but the fewer number of calories

The upshot: A keto diet that is high in fat and low in healthy whole foods (such as vegetables, fruit, grains, legumes), because they fear carb content of these nutrient-packed fiber-filled plant-based foods, is not only bad for your health, it also doesn't work for long-term weight loss or maintaining a lower set point.

The study conceded that initial weight loss on keto will bring down markers for cardiovascular disease such as cholesterol and blood pressure as the person loses weight, but that in the long haul, these markers go back up, as the dieter has trouble sustaining the weight loss of the early days of the diet.

Keto, for anyone who has not been following the diet trends of the past two decades, refers to ketones, which are released when your body achieves a state of ketosis, or burning fat as fuel instead of carbohydrates and continues to operate on this fat-fuel to lose weight faster. Celebrities like Halle Berry and the Kardashians, Lebron James, and tech founders have all used keto dieting to shed fat fast. The issue is that it relies on eating a diet high in fat and protein usually from animal sources that are high in saturated fat, known to raise cholesterol, promote plaque deposits, eventually clog your arteries and lead to heart disease.

Keto and Low-Carb Diets Only Work in the Lab, Since Humans Appear to Like Carbs

One reason is that the keto diet is difficult to stick to since it involves keeping carbohydrate input to a minimum -- less than 30 percent of your overall calories, or even lower. The exception: Lab animals that are put on a keto diet were able to stay healthy and on a diet such as a keto, Paleo, or intermittent fasting, all popular diets since researchers were able to control their food intake. But humans are another story and generally speaking, life gets in the way, in the form of birthdays, cravings, and favorite foods that are often carb-loaded.

The best bet, for long-term heart health and living an active healthy lifestyle that includes maintaining a healthy weight, according to Dr. Andrew Freeman, a cardiologist who conducted the Denver study, is a diet high in fruits and vegetables, whole grains and legumes, nuts, and seeds, and low in animal fat.

Here are other recent studies that prove Keto is hard to follow and harmful to health

In a review study of half a million people, a ketogenic diet–defined as limiting carbs to less than 50 grams a day, or about two apples' worth–was linked to higher rates of tumors as well as high blood pressure. One reason that a low-carb diet is found to promote cancer risk is that it relies on eating more saturated fat, found in butter, full-fat milk, and red meat, plus carcinogens found in processed meats.

So keto dieters try to stay away from fruits and vegetables (which have complex carbs) in favor of unhealthy protein and fat sources. The author found that no matter where you live on the globe, limiting an entire food group such as fruit and vegetables, is bad for your health.

The author writes: "Some benefits of going keto are difficult to dispute. Following a high-fat, low-carb diet can be a solid strategy for rapid weight loss and blood-sugar control." But the flip side is that all that fat will clog up the system, mess up your metabolism and eventually make your body less tolerant of carbs when you do eat them, so going back to a normal diet can lead to gaining the weight back and then some.

One study looked at The Pima, a group of Native Americans from what is now the U.S. Southwest, who went from eating a traditionally high-carb diet to a modern high-fat diet, which led to an increase in non-insulin-dependent diabetes over the last century. When researchers studied The Pima and Caucasian groups in a study of diet over 14 days, a high-fat diet led to a "decrease in oral glucose tolerance" among both groups.

Essentially after eating a diet high in fat, when carbs were introduced, the researchers saw "Deterioration in carbohydrate metabolism and lipoprotein changes induced by a modern, high-fat diet" in both the Pima population and in Caucasian groups, equally. So eating more fat makes your body less able to metabolize carbs when you do end up adding them back in.

Diets That Are High in Red Meat and Saturated Fat Lead to Cancer Growth

Twenty-two experts from 10 countries reviewed more than 800 studies to reach their conclusions that cancer is a byproduct of a meat-heavy diet: Eating 50 grams of processed meat every day increased the risk of colorectal cancer by 18%. That’s the equivalent of about 4 strips of bacon or 1 hot dog a day. For red meat, the researchers saw an increased risk of colorectal, pancreatic, and prostate cancer in those who eat red meat every day. The exhaustive study also showed eating lesser amounts of meat contributes to cancer. Their conclusions: Meat and dairy can also contribute to inflammation in the body, which can help cancerous tumors form and grow.

Yo-Yo Diets contribute to lower metabolism, increased mortality

Keto is so hard to stay on, that long-term effects are hard to study. When asked if a keto diet could be effective against brain disorders such as Parkinson's or Alzheimer's (because it was shown to work against seizures in children), in a Harvard Health Publishing review, Marcelo Campos, MD, writes that it's unknown, since no one stays on a keto diet long enough to measure. "We do not know much about its long-term effects, probably because it’s so hard to stick with that people can’t eat this way for a long time," He added: "It is also important to remember that “yo-yo diets” that lead to rapid weight loss fluctuation are associated with increased mortality."

One measure of a successful diet is that you can sustain it. Keto is too strict to stay on

At the University of Chicago Medicine, dietitians have stated that the keto diet "is extremely strict and difficult to maintain." In an article on the risks they listed:

  • More often than not, it’s not sustainable. Oftentimes weight gain may come back, and you’ll gain more than what you lost
  • The keto diet could cause low blood pressure, kidney stones, constipation, nutrient deficiencies, and an increased risk of heart disease. Strict diets like keto could also cause social isolation or disordered eating. Keto is not safe for those with any conditions involving their pancreas, liver, thyroid, or gallbladder.
  • Someone new to the keto diet can also experience what’s called the “keto flu” with symptoms like upset stomach, dizziness, decreased energy, and mood swings caused by your body adapting to ketosis.

Keto Diets Are Bad for Bone Health in Athletes, a New Study Found

The New York Times picked up on a study that was first published in Frontiers in Endocrinology, that found a keto diet may "alter bone health in athletes" such as runners, who are prone to stress fractures and joint injury. The study tracked male and female race walkers over several weeks of intense training, and found that those who followed a keto diet developed "early signs indicative of bone loss." So not only do you gain the weight back but in the meantime, you've weakened your bones, a perfect storm for stress fractures to form since a heavier footfall, due to rapid weight regain, can lead to more impact stress on the smaller bones, especially for distance runners.

In the study, the data found that a Low-Carb, High-Fat Diet led to the loss of bone density: "Our data reveal novel and robust evidence of acute and likely negative effects on the bone modeling/remodeling process in elite athletes after a short-term ketogenic Low-Carb, High-Fat Diet." The study added:  "Long-term effects of such alterations remain unknown, but may be detrimental to bone mineral density (BMD) and bone strength, with major consequences to health and performance." It went on to say the diet may hinder bone healing and recovery, and lead to a reduced performance by athletes who sustain high-intensity endurance:

"While ketogenic diets are of interest to athletes due to their ability to induce substantial shifts in substrate metabolism, increasing the contribution of fat-based fuels during exercise, we have previously reported the downside of a concomitantly greater oxygen cost and reduced performance of sustained high-intensity endurance exercise."

The study added: "LCHF diets are associated with impaired bone growth, reduced bone mineral content, compromised mechanical properties, and slower fracture healing. Furthermore, increased bone loss has been reported in children with intractable epilepsy placed on a medically supervised LCHF diet for 6 months." So Keto is not so helpful to athletic performance or healthy bones for anyone, it turns out.

In a review of the side effects of keto diets for Health, experts explain that the weight you lose maybe more muscle than fat, but the weight you regain will be more fat than muscle, which ends up lowering your metabolism.  “You’ll lose weight, but it might actually be a lot of muscle,” she says, “and because muscle burns more calories than fat, that will affect your metabolism—especially if you’re eating more fat than protein."

The best diet, according to Dr. Freeman, is one you can stay on, which is a heart-healthy mix of high-fiber whole foods, mostly fruit, vegetables, whole grains, seeds, nuts, and legumes.

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