Are keto diets safe?

The popularity of the keto diet is from its ability to help lose weight in a relatively short time. Unfortunately, there are some serious and life-threatening consequences of this unnatural way of eating. Studies have shown that low-carb diets increase all-cause mortality by 32 percent, and mortality from heart disease and cancer were increased by 51 percent and 35 percent, respectively.

Understanding the keto diet

Blood sugar, also known as blood glucose, is the universal go-to fuel for the cells throughout our bodies. Our brain burns through a quarter pound of sugar a day, which is its “preferred metabolic fuel.” If we stop eating carbohydrates or stop eating altogether, most of our cells switch over to burning fat. But fat has difficulty getting through the blood-brain barrier. Your liver can turn fat into ketones, which can then breach the blood-brain barrier and sustain your brain if you’re not getting enough carbohydrates.

Switching fuels has such an effect on brain activity that it has been used to treat epilepsy. The prescription of fasting for the treatment of epileptic seizures dates back to Hippocrates. Ketogenic diets started to fall out of favor in 1938 with the discovery of the anti-seizure drug that would become known as Dilantin, but ketogenic diets are still in use today as a third- or fourth-line treatment for drug-refractory epilepsy in children.

Keto diet and weight loss

Initial weight loss in the first one or two weeks of being on a keto diet gets everyone excited, but what is happening inside their bodies tells a totally different story.

In reality, ketogenic diets cause metabolic disadvantage and slow the loss of body fat. If you cut about 800 calories of carbohydrates a day from your diet as you would do on a keto diet, you lose 53 grams of body fat a day, but if you cut 800 calories of fat as you would do on a low-fat diet, you lose 89 grams a day. Cutting the same number of calories is about 80 percent more fat loss when you cut down on fat instead of carbs.

What is lost is lean body mass --water and muscle. That is why a study showed that the leg muscles of CrossFit trainees placed on a ketogenic diet may shrink as much as 8 percent. So, a ketogenic diet may not just blunt the performance of endurance athletics, but strength training as well.

Keto diet and diabetes

Claims that a ketogenic diet can treat and reverse diabetes are everywhere on the internet and in books. But they are confusing the symptom — high blood sugars — with the disease, which is carbohydrate- intolerance. People with diabetes can’t properly handle carbohydrates, and this manifests as high blood sugars. Sure, if you stick to eating mostly fat, your blood sugars will stay low, but you may be actually making the underlying disease worse. There are multiple lines of evidence contradicting the belief that “carbs cause diabetes, so low-carb diets cure diabetes.”

First, most intervention studies on ketogenic diets are short-term, but the limited evidence available from studies with longer follow-up periods indicates that the beneficial effects of ketogenic diets on biomarkers dissipate over time, long-term adherence is difficult and there are higher rates of kidney stones, osteoporosis, and hyperlipidemia.

There are epidemiological, or population-based studies, which consistently demonstrate that reducing carbohydrate intake increases the risk of diabetes.

--The Health Professionals Follow-Up Study tracked more than 40,000 U.S. men who were free of type 2 diabetes at baseline for up to 20 years and found that those who ate a low-carbohydrate diet rich in animal fat and protein were 37 percent more likely to develop diabetes.

--Vegans – who naturally eat a high-carbohydrate diet – were found to have half the risk of developing type 2 diabetes as meat-eaters, even after adjusting for physical activity and body mass index. In other words, even overweight and sedentary vegans had a reduced risk of diabetes because of eating carbohydrate-rich plants.

In short, while ketogenic diets may lead to temporary improvements in glycemic control, they lose their effectiveness over time, are fundamentally unnatural to humans and are unable to prevent the life-threatening complications of diabetes.

Keto diet and cancer

A common refrain is that “cancer feeds on sugar.” But all cells feed on sugar. Cancer can feed on ketones, too. Ketones have been found to fuel human breast cancer growth and drive metastases in an experimental model — more than doubling tumor growth. Some have even speculated that may be why breast cancer often metastasizes to the liver, the main site of ketone production. Researchers are even considering designing ketone-blocking drugs to prevent further cancer growth by halting ketone production.

And think about what eating a ketogenic diet might entail. High animal fat intake may increase the mortality risk among breast cancer survivors and potentially play a role in its development in the first place through oxidative stress, hormone disruption or inflammation.

In men, a strong association has also been found between saturated fat intake and prostate cancer progression. Those in the top third of the consumption of fat-rich animal foods appeared to triple their risk of dying from prostate cancer. Not necessarily fat in general, but saturated fat intake may negatively impact breast cancer survival, a 50 percent increased risk of dying from breast cancer.

There’s a reason the official American Cancer Society and American Society of Clinical Oncology Breast Cancer Survivorship Care Guidelines recommend a dietary pattern for breast cancer patients that’s essentially the opposite of a ketogenic diet: high in vegetables, fruits, whole grains, and legumes -- beans, split peas, chickpeas and lentils -- and low in saturated fats.

Keto diet and Alzheimer’s disease

A ketogenic diet leads to glucose and lipid dysregulation, which has repeatedly been shown to create harmful byproducts, as well as deposition of amyloid and tau proteins that are known to be strongly associated with end-stage Alzheimer’s disease.

Keto diet and osteoporosis

What about bone loss? Sadly, bone fractures are one of the side effects that disproportionately plague children placed on ketogenic diets, along with growth stunting and kidney stones. Ketogenic diets may cause a steady rate of bone loss, as measured in the spine, presumed to be because ketones are acidic, and so, keto diets can put people in what’s called a “chronic acidotic state.”

Keto diets and heart disease

The health effects of a typical low-carb ketogenic diet, like Atkins, are vastly different from a low-fat plant-based diet, like the Ornish diet. They would have diametrically opposed effects on cardiovascular risk factors in theory, based on the fiber, saturated fat and cholesterol contents of their representative meal plans. And when actually put to the test, low-carb diets were found to impair artery function. Over time, blood flow to the heart muscle itself is diminished on a low-carb diet. Heart disease actively worsens on low-carb diets but may be reversed by an Ornish-style diet.

Based on the Harvard cohorts, eating more of an animal-based low-carb diet was associated with higher death rates from cardiovascular disease — a 50 percent higher risk of dying from a heart attack or stroke.

“Given that heart disease is the No. 1 killer of men and women, recommending any diet that a patient will adhere to in order to lose weight seems irresponsible. Why not tell people to smoke? Cigarettes can cause weight loss, too, as can tuberculosis and a good meth habit, but the goal of weight loss is not to lighten the load for your pallbearers.” said Dr. Michael Greger, founder of nutritionfacts.org.

  

Dr. Padmaja Patel is medical director of the Lifestyle Medicine Center.