By Caroline Shannon-Karasik
Dec 12, 2018 @ 10:00 am
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Chances are likely you’ve heard a thing or two about the keto diet by now. Whether it’s because your co-worker won't stop talking about it, or you're an avid follower of Kourtney Kardashian (she’s reportedly a huge fan of keto), talk of the high-fat, low-carb diet lifestyle has most definitely made it's way to you.

But that doesn't mean you've got all the rules down pat. Like, is it really all protein and butter, and is a high-fat diet really the way to go? If you’ve got questions about keto, we've got the answers, including what you can eat, why it helps with weight loss and whether or not it’s sustainable over the long haul.

What Is Keto?

Here is the gist, according to Ryan P. Lowery, Ph.D., co-author of The Ketogenic Bible: The ketogenic plate is divided into three parts — low carbs, high fats, and a moderate portion of protein — but with a different approach than the Atkins diet. The goal, Lowery says, is for your body to switch from relying primarily on glucose (from carbohydrates) to fueling itself on ketones (from fat).  

“By limiting the sugar and carbohydrates in your diet, your body starts to burn fat at a higher rate, thereby producing ketones that your body starts to utilize,” he says.

Sydney Greene, R.D., a registered dietitian at Middleberg Nutrition in New York City, says the keto diet was originally introduced by doctors in the early 1900s as a means for treating epilepsy. The idea behind it — according to a 2008 report on the uses of the diet for epilepsy and other neurologic illnesses — is that researchers discovered fasting has anti-seizure applications and the keto diet is thought to “simulate the metabolic effects of starvation by forcing the body to use primarily fat as a fuel source.”

What Can I Eat?

OK, so by now you know that the diet is low in carbohydrates and high in fat — and inspired by literal starvation, which, sure, sounds pretty suspect. So what does that really mean in terms of what you can eat?

Greene says a general outline of the foods that can be eaten, includes the following:

  • Fruits — minimal, but can include raspberries, blackberries and blueberries
  • Veggies — spinach, kale, fennel celery, cucumber, cauliflower, broccoli, bell peppers, and zucchini
  • Healthy fats — nuts, olive oil, avocados, ghee (like one of Fourth & Heart’s many grass-fed varieties), nut butter and seeds
  • Protein — Poultry, fish, beef, bone broth, full-fat cheeses, plain Greek yogurts and eggs from organic and/or grass-fed sources

On the other hand, Greene says you’ll want to avoid the following foods:

  • Starchy veggies — sweet potatoes, butternut squash, spaghetti squash and beets, as well as other root vegetables, like carrots and parsnips
  • Fruit —  Most varieties, including tropical fruits like bananas, mango, pineapple and papaya
  • Processed carbohydrates — Bread, crackers, and junk food
  • Other carbohydrates  — Grains, legumes, and corn

As a general rule of thumb, Greene says you'll want to keep your net carb intake to no more than 15 to 20 grams a day. For reference, one small apple is about 15 grams of carbohydrates, so that gives you an idea of what you can expect.       

Why Do People Use It To Lose Weight?

Mainly, Greene says keto is most often used for short-term, quick weight loss. Basically, people who subscribe to the diet have seen significant weight loss in a fairly short amount of time (take, for example, Sherri Shepherd’s 25-pound transformation).

But, Greene cautions, if the proportions of protein, carbs and fat are not maintained, then “weight loss will plateau or even come back.” Lowery maintains adds that he sees the keto diet as a way for people to get control over their appetite.

“With all of the processed foods and sensory overload that we get from commercials, ads and so forth, most people are controlled by their appetite and not the other way around,” he said. “However, if you can put appetite back in your control and stop riding what we call the ‘carb/insulin rollercoaster’ of periodic ups and downs throughout the entire day, then you will undoubtedly look and feel better.”

He added: “It’s important to point out that there are a million different ways you can lose weight, but ultimately that isn’t what people want. People want to improve their body composition, meaning lose fat and maintain or gain muscle. In research and in a real-world application, a well-formulated ketogenic diet has been shown to do this over and over again.”

What Are Some Other Benefits?

Lowery says beyond losing body fat, studies show that the keto diet can help improve mental clarity, reduce appetite and increase fullness, improve blood lipid profiles (cholesterol levels and triglycerides), reduce blood sugar and insulin, improve blood pressure and increase energy. It's a good idea to talk to your doctor to see if your any of this is an area of concern for you personally. Neurological disorders, like Alzheimer’s and Parkinson’s diseases, have also shown to benefit from a keto lifestyle.

Are There Any Downsides?

Like any significant dietary change, Lowery says the keto diet will bring with it an adaptation period. Some people say they experience the “keto flu” when the first start the diet, as a result of a host of symptoms — common side effects include nausea, diarrhea, headaches and irritability — that mimic the actual flu.

“The best way to understand this is that your body has been primarily running on glucose and carbohydrates for 30 or 40 or 50 or 60 years of your life,” Lowery says. “It’s going to take more than 72 hours for your body to switch its fuel source from primarily glucose to primarily ketones.”

Greene says the diet’s reduction in complex carbohydrates — and, therefore, fiber — can also lead to constipation.

She added: “I highly recommend working with a healthcare professional if you are going to embark on this diet, as vitamin and mineral deficiencies can occur if proper attention is not paid to including fruits and vegetables, and supplementing when needed.”