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What is keto: the fat-burning diet

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Drilled down to its essence, the ketogenic diet (keto for short) is low on carbs and high in fats and proteins. Because there is little blood sugar from food circulating in the bloodstream, the body will start burning stored fats for energy. This makes it an extremely efficient diet for weight loss, helping people lose many kilograms in a very short time span.

Keto is a very restrictive diet, which is why many fail to follow through, giving up before they can reap the full weight-loss benefits. Many also either consume too much protein or too many poor-quality fats from processed foods, sometimes both. The carb restrictions also mean keto followers eat very little fruits and vegetables, or none at all.

Obviously, this can be a problem as studies have shown time and time again that a diet rich in vegetables and fruits can lower blood pressure, reduce the risk of heart disease and stroke, prevent some types of cancer, lower risk of eye and digestive problems, and have a positive effect upon blood sugar, which can help keep appetite in check.

In short, keto can be an extremely effective weight loss diet but it could also cause some health problems if it is followed improperly. Additionally, some patients with underlying health conditions, such as kidney disease, should stay away from it as the diet might worsen their condition. Another thing to keep in mind is that, like with any fad diet, many end up regaining the weight they quickly lost soon after they get off the keto bandwagon.

How does keto work?

The body uses sugars to generate energy for cellular processes. But if a person’s carbohydrate intake is very low or non-existent, the body will start breaking down stored fats into molecules called ketones. It does so through a process called ketosis, hence the name of the diet, which typically starts 4-5 days after a person eats fewer than 20-50 grams of carbs per day. At this point, cells will use ketones for energy until a person starts eating carbs again.

“​The Keto diet is an extremely low-carbohydrate diet (minimal carbohydrates), high protein/high fat diet. It is similar to the Atkin’s or other low-carb diets out there, but the difference is, if done CORRECTLY, you put your body into a state of Ketosis, meaning, that instead of using the preferred substrate for muscles and brain cells (glucose), your body is using primarily ketone-bodies which derive from fat molecules. This type of diet basically is teaching your body to burn fat and use it as fuel instead of glucose,” Dana Ellis Hunnes, Adjunct Assistant Professor at the Department of Community Health Sciences at UCLA, told ZME Science.

It’s not yet entirely clear why ketosis causes weight loss. One hypothesis is that ketosis suppresses appetite and may affect hormones like insulin that regulate hunger and metabolism. Since fats and proteins are more satiating, people may feel fuller on a lower calorie diet.

​”In the short-term consequences may include less insulin response to meals since you are eating minimal carbohydrate which may be good for blood glucose levels and diabetes.  However, with this in mind, many fibers come from carbohydrate-rich foods and without those in the diet, it may be more difficult to eliminate (have bowel movements) regularly.  long-term consequences include potential increased risk for heart disease since it is such a high-protein, high-fat diet (though, this may be reduced (the risk) if healthy plant-based fats are the primary sources of fats instead of saturated/animal-based fats).  There is a possibility of weight loss, but to me, the risk to vascular system is not worth it,” Hunnes said.

Types of keto diet

Although keto is a fad diet that has risen to prominence in the last decade, it is not by any means new. The keto diet was first designed in the 1920s by doctors looking to treat epilepsy. For reasons not entirely understood even to this day, fueling cells with ketones instead of glucose reduces the number of seizures experienced. Although there are now anti-seizure medications, some patients who don’t respond to treatment can still reap benefits by going on keto.

But since then, keto has been recognized for its weight loss potential. For instance, in the 1970s, Dr. Atkins popularized his famous low-carb weight-loss diet, which starts with a two-week ketogenic phase.

Like all diets, there is no single plan and every individual is different. However, any plan that calls for eating fewer than 50 grams of carbs a day can be called keto.

Some versions of the ketogenic diet include:

  • Standard ketogenic diet: 75% fat, 20% protein, and 5% carbs
  • Cyclical ketogenic diet: intermittent ketosis coupled with periods of higher-carb intake. Example: 5 ketogenic days followed by 2 high-carb days.
  • Targeted ketogenic diet: standard keto with added carbs around workouts.
  • High-protein ketogenic diet: 60% fat, 35% protein, and 5% carbs.

What are the benefits of keto?

We have nearly 100 years of evidence that ketosis reduces the frequency of seizures, sometimes on par with modern medication. Due to its neuroprotective effects, keto may help with other brain disorders such as Parkinson’s, Alzheimer’s, multiple sclerosis, sleep disorders, and autism. However, studies supporting the use of ketosis to treat such conditions are limited or lacking at the moment.

However, the main use and benefit of keto is tied to weight loss. For patients with type 2 diabetes, for which being overweight or obese can be life-threatening, keto and other low-carb diets might prove particularly advantageous.

One small study found that 7 of 21 overweight participants with type 2 diabetes were able to stop using medication after they consumed less than 20 grams of carbohydrates per day over the course of 16 weeks. Because the ketogenic diet “can be very effective at lowering blood glucose, patients on diabetes medication who use this diet should be under close medical supervision or capable of adjusting their medication,” the researchers wrote.

In yet another study on 49 volunteers with obesity and type 2 diabetes, researchers found that 95% of those on the ketogenic diet were able to stop or reduce diabetes medication compared to 62% on a low-glycemic, reduced-calorie diet (500 kcal/day deficit).

However, things can get complicated. A 1991 study on 12 Pima Indians and 12 Caucasians, all nondiabetic, found that a high-fat modern diet (50% fat and 30% carbohydrate) was associated with a decrease in glucose tolerance and higher cholesterol. In other words, a high-fat diet might actually put people at risk of developing diabetes.

There’s also something to be said about the quality of food. Replacing carbs with animal fats and proteins can be tricky to pull off in a healthy and sustainable manner. Most people turn to beef, pork, lamb, chicken, and cheese, which are associated with increased mortality and inflammation. Instead, using plant-derived fats and proteins would be less risky — something not at all accessible to most people who are already on a very restrictive diet.

“I do not advocate a keto diet for pretty much anyone except those who the keto diet was originally designed for – patients who have severe epilepsy/seizure disorders.  Most people who go on a “keto” diet are not doing it correctly, meaning they are eating too many carbohydrates to really get into a state of ketosis which can be measured in the urine or blood.  Moreover, if you lose weight too quickly as can happen with this type of diet, again, especially if not doing it correctly, you can lose significant amounts of muscle as your body feels it is in starvation.  micronutrient deficiencies are also possible, again because of the low-carb (even from produce) diet,” Hunnes said.

“My go-to diet of choice is a whole-foods, plant-based diet.  Studies time and again demonstrate a whole-foods plant-based diet can reduce the risk of a myriad of chronic diseases (cancers, stroke, heart disease, obesity, diabetes) and is full of fiber, water from the foods themselves, micronutrients (vitamins and minerals), potassium, and sufficient in protein.  It is also far better for the environment than a keto diet high in animal products would be as it requires less water, less land, and produces far less greenhouse gases,” she added.

Is keto safe?

Not much is known about the long-term effects of keto, specifically. However, studies suggest that low-carb diets reduce lifespan compared to those consisting of moderate carbohydrate intake.

A 2018 study that followed 15,428 American adults aged 45-64 years from 1987 until 2012 correlated health outcomes with diet. According to the results, over a 25-year period, people who had a moderate carbohydrate intake (50-55% of daily calories) had an average life expectancy of 83 years — that’s four years longer than those with low carb intake (40%), who lived only 79 years on average. Participants with high carb intake (more than 70% of daily calories) had an average life expectancy of 82 years, slightly lower than the moderate carbs intake group.

Another long-term study published in The Lancet by researchers at Brigham and Women’s Hospital in Boston looked at the dieting habits of a staggering 432,000 people in more than 20 countries. The results suggest that those who consumed a moderate amount of carbs (around half of their daily calories) lived the longest. Conversely, those who had a diet of more than 70% carbs or less than 40% carbs were more likely to die earlier than those in the moderate carb-intake group.

Previous studies showed that low carbohydrate diets are beneficial for short-term weight loss and reduce cardiometabolic risk. In the long-term, however, low-carb diets seem to shave off 4-5 years of lifespan compared to moderate-carb intake.

“​I would really only recommend a keto diet under the advisement of a dietitian who specializes in a ketogenic diet (and those dietitians typically work at major medical centers with patients who have severe epilepsy and seizures).  This type of diet is ripe for increasing the risk of micronutrient deficiencies in people who eat it without proper counseling.  It is also a recipe for increasing the risk of certain cardiovascular diseases.  Even in people who have severe epilepsy/seizures, this type of diet is generally followed for 6 months to a year maximum and then regular foods are re-integrated.  Those would be my recommendations,” Hunnes concluded.

Bottom line: keto can help overweight people to shed weight fast, however, you risk reverting back to your previous weight just as quickly as you lost those pounds after getting off the diet. Keto is often called a “yo-yo diet” for good reason. 

Patients suffering from seizures and type 2 diabetes might reap additional benefits from keto, particularly thanks to improved blood sugar control. However, the long-term effects of keto are unknown and even the most die-hard fans of keto agree that people shouldn’t stay on a ketogenic diet more than a couple of months per year. 

It may sound cliche, but like most things in life, the key to a healthy life is moderation. Consuming around 50% carbohydrates relative to daily calories seems to hit the sweet spot.

A balanced, unprocessed diet, rich in fruits and vegetables, lean meats, fish, whole grains, nuts, seeds, olive oil, and lots of water seems to show the best evidence for a longer and healthier life.