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A Cardiologist’s Take on the Keto Diet

Keto Diet Foods
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There’s a question making the rounds on the internet that has a spectrum of answers: Is the keto diet healthy?

The truth is, while the little-to-no carb, high-fat diet can dramatically help shed pounds, there haven’t been any long-term, randomized clinical studies to help determine the long-term effects on the body. Most studies to date are smaller scale, and they’re filled with both positives and negatives. Some suggest it improves blood sugar in diabetics and lessens cardiovascular risk factors, like obesity. Others report spikes in “bad” cholesterol, heart problems, and hypoglycemia. To add to the uncertainty, its effectiveness as a weight loss treatment hasn’t even been clinically proven, experts have said. What’s left is anecdotal evidence and people from all corners of the web — including physicians, nutritionists, and celebrities — raving or ranting about it.

“I am open-minded when patients come to us with diets or nutritional trends, especially because I appreciate that they have taken an interest in their health,” said Neel Chokshi, MD, MBA, an associate professor of clinical medicine and medical director of the Sports Cardiology and Fitness Program at Penn Medicine. “We often don’t have a lot of data to guide us on the positive or negative effects, so I am cautious to say this is the right thing to do and not the right thing to do. I think that diet is important, and I have a personal interest in many of these approaches to nutrition, but what I share with patients is mostly my informed opinion based on as much science as possible.”

Changing Fuels

In its strictest form, the keto diet consists of 75 percent fats, 20 percent protein, and five percent carbohydrates. That means foods like healthy meats and cheese are fair game, but no more bread, rice, or soda. Under regular circumstances, cells in the body use carbohydrates as a source of energy, which is converted into glucose and sent into the bloodstream. But depriving the body of that source forces it to go after fats, which is known as “ketosis.” During ketosis, the body breaks down fat molecules into something called ketone bodies to generate energy. 

“It’s a catabolic process in some sense. It breaks down fat and muscle mass if you don’t take on calories,” Chokshi says. “And so, generally people see the weight loss and feel better.”

The main issue is that ketosis is arguably a backup mechanism for fuel and energy for the body, he says. There have been many positive effects reported, but researchers don’t understand the long-term effects of sustained keto-based nutrition.

Beyond Weight Loss

Even though he isn’t a fan of diets in general – “I prefer habits,” he says – Chokshi recognizes the benefits of keto for some patients looking to lose weight and make a healthy change in the short term. Many have had success with dropping pounds, he says, and reported feeling “healthier and more fit.” It’s even better if it kickstarts a more sustainable heathy lifestyle.

He also suspects there are some benefits for the heart and reversing diabetes since it has been shown to improve insulin sensitivity. That’s supported by several studies, like a 2017 review in the journal Nutrients that found that the keto diet improved HDL “good” cholesterol levels and helped reverse the course of type 2 diabetes in patients by controlling blood sugar levels, though “usually in limited time,” the researcher wrote.In 2018, another study in the  journal Diabetic Medicine found the keto diet in patients with type 1 diabetes was associated with “excellent levels” of blood sugar. 

“I can see a potential benefit because diabetes is exacerbated by excessive carbohydrate intake,” he says. “Short periods of ketogenic diet coupled with long-term lifestyle changes could potentially reverse that by increasing insulin sensitivity.”

Higher HDL cholesterol levels and lowering blood sugar are also associated with lower risk of heart disease.

Choose Wisely

Still, there are potential downsides that patients need to watch out for, Chokshi says. Keto entails a significant portion of calories from fat, but not all fats are created equal. Consuming a lot of saturated fats, like the ones found in fast food and red meat, increases a person’s risk for atherosclerosis, which promotes coronary disease and heart attacks. Healthier fats — called monounsaturated and polyunsaturated fats — are found in foods like eggs, fish, and nuts. 

Additionally, keto can lead to a sudden surge in LDL and triglycerides, the “bad” cholesterol, when the diet is initiated, a surge that may level out after weeks and months. One of Chokshi’s patients who was doing keto rigorously saw his LDL cholesterol shoot up for a few months.

But, in the short term, having elevated LDL and triglycerides probably doesn’t do much in term of increasing a person’s risk of cardiovascular disease, Chokshi says. “High cholesterol levels that persist over months to years are more concerning.”

Loose Link

There is one recent long-term study suggesting a risk for heart disease. It came from a group of Chinese researchers who presented a study at the American College of Cardiology annual meeting in New Orleans. They found patients who followed a diet low in carbohydrates for nearly two decades had an increased risk for atrial fibrillation. 

But there are important caveats to consider. While the study suggests a link between the two, it wasn’t a randomized trial, so it doesn’t show a cause and effect, and the participants weren’t on the keto diet. They self-reported their carbohydrate intake and those with lower intake (about 44 percent of their calories – which is higher than the keto diet) were found to have higher rates of the disease.

“Only a very limited portion of the data and study was presented at the meeting, but it’s a very loose association,” Chokshi says. “It’s an interesting hypothesis, but there are too many variables involved to draw definitive conclusions here.”

The researchers proposed that those at risk were probably eating fewer vegetables, fruits, and grains, which are known for being inflammation-fighting foods. And inflammation is a known risk factor for AFib.

Not the Villain

“Carbs, in general, have gotten a lot of bad press,” Chokshi says. “But we are learning that processed foods and processed carbs are the real culprit here.”

Some of his patients go on the keto diet faithfully, while others opt for a diluted version of it, where they lower their carb intake, but not to the degree that keto calls for – which he believes to be a reasonable compromise.

“I think it’s OK to eat natural carbs, such as whole fruits and vegetables, especially those with fiber content. They are necessary not only for caloric intake but for vitamins and nutrition,” he says. “I try to get people to avoid extremes for extended periods of time, as the long-term effects of prolonged ketosis on the body are unknown.”

What some people may not know is that sleeping, and not just the diet, can cause the body to go into ketosis, assuming it’s for eight hours and no food is consumed three to four hours before going to bed.

“I think that’s a more natural way of inducing ketosis, which is to go to bed slightly hungry and not full,” he says. “And then you wake up, and have the effects of ketosis, a decreased hunger drive. For most people, I encourage that.”

Lasting Impact

Keto isn’t new. It’s been used for decades to successfully treat epileptic children. But only relatively recently has it become more popular among adults looking to lose weight. It follows similarly low-carb diets, like Atkins, a popular approach back in the early 2000s that has since fallen to the wayside. 

Chokshi thinks the keto diet likely has positive effects that are arguably attributable to other diets, as well.

“People who are dieting are more likely to pay attention to the food they’re putting into their bodies, with likely no excessive caloric intake. Higher fat and protein diets have greater satiety – if you feel full, you are less likely to eat too much,” he says. “In counting carbs vs. proteins vs. fats, you are paying attention to the quality of foods you consume, eating fewer processed foods, which is generally healthier.

“Lastly, you form routines around meals and consumption which are sustained over time and lead to positive changes in weight and sense of well-being.”

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