Lifestyle

The pros and cons of the keto diet, the latest weight-loss trend

In the 1920s, a team of physicians at the Mayo Clinic developed a high-fat, low-carbohydrate dietary program for epilepsy patients called the ketogenic diet. They could hardly have guessed that almost a century later, their findings would reemerge as a hot weight-loss trend.

The goal of the ketogenic (or “keto”) diet is to induce ketosis, a metabolic state in which the body, unable to convert carbohydrates into glucose, burns fat instead, which the liver converts into water-soluble molecules called ketone bodies that take the place of glucose as an energy source.

The keto diet’s fat-burning properties have endeared it to the so-called biohackers of Silicon Valley, along with those who want a weight-loss plan with more scientific grounding than most fad diets.

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To those who remember the Atkins diet and the early-2000s low-carb craze it briefly sparked, the keto diet may not sound like anything new. What sets it apart, according to dietitian Nathan Diaz, is that it actively encourages fat consumption.

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“This is the first diet we’ve seen that has said, ‘If you eat high amounts of fat, very low amounts of carbohydrates, and moderate amounts of protein, you can see weight loss happen,’ ” says Diaz. “The Atkins diet more so just limited carbohydrates; it wasn’t as restrictive as the ketogenic diet.”

According to Bruce Bistrian, an associate professor in pediatrics at Harvard Medical School and chairman of the executive committee for the school’s Division of Nutrition, the state of ketosis itself can also reduce hunger symptoms, which can help some of the diet’s adherents lose weight without having to consciously restrict their caloric intake.

Bistrian, however, does not recommend that people start the diet without consulting a professional first.

“If people are doing it to achieve weight loss, it’s probably best to do with some medical supervision and some agreement by medical personnel that it’s something you should do,” says Bistrian.

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As a clinical dietitian specialist with Massachusetts General Hospital, Heidi Pfeifer has used the ketogenic diet for 20 years to treat epilepsy. (While heightened levels of ketone bodies in the bloodstream have been shown to reduce epileptic seizures, especially in children, anticonvulsant drugs have largely replaced the diet in modern epilepsy treatment.) She sees great benefits to using the keto diet for weight loss, especially since it gets people to stop fueling their bodies with sugar.

Meals tend to include protein — meats, eggs, cheese, nuts — and vegetables. Grains, beans, even fruits are eliminated or restricted. And forget about alcohol.

“As you’re converting over from using carbs to using fats, [energy levels are] more sustained — you don’t have the mid-day slumps, so you can go throughout the day with a better energy source,” says Pfeifer.

She agrees with Bistrian that it’s crucial to keep your physician involved, since the diet causes such drastic changes to one’s metabolism.

“If they do blood work, they’re going to see positive ketones, which is not what we in general want, but for this diet, yes, it is what we want,” says Pfeifer. “So when their physician is looking at their levels, they are going to be off.”

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There’s also the question of whether the diet is a practical long-term solution to weight loss. On this point, Diaz has his doubts.

The goal is to induce ketosis, a metabolic state in which the body, unable to convert carbohydrates into glucose, burns fat instead.

“You’re eating a lot of meats, oils, butters, cheeses, creams. . . . People tend to not want to eat that all the time,” says Diaz. “So you do see a very quick drop-off rate with this diet due to the fact that they can’t sustain it.”

Since the keto diet requires one to remain in a state of ketosis, there’s very little margin for error.

“Let’s say Monday to Friday you’ve been killing it, you’re in that ketosis range . . . but on Saturday night, you go absolutely buck-wild and have a high intake of carbs,” says Diaz. “You can easily knock yourself out of ketosis, and it’s very hard to get back in it.”

Brigid Thomas of Marlborough had tried dieting countless times without seeing results before stumbling across the keto diet online and deciding to give it a try. She’s been on the diet since February, and has had such a positive experience that she now proudly rocks the Instagram handle @_bostonbrigidgoesketo.

“I’ve really enjoyed it; I’ve felt like it’s been rather easy to follow,” says Thomas. “You’re eating mostly fats and proteins, it’s really just cutting out that white sugar and stuff. And the flour.”

The support of her fellow dieters has also been essential.

“My biggest tip would be to find a support group online,” says Thomas. “What really kept me on point was that, if I had a question or was feeling down about myself, I could go talk to these people, tell them what I was going through, and get a lot of support.”

Pfeifer offers two other important factors to keep in mind: hydration and nutrition.

“Especially because you’re not holding onto fluids, you need to make sure you’re keeping hydrated,” says Pfeifer. “As you’re taking out a huge portion of a macronutrient, the carbohydrates, you also need to make sure that you’re getting all your vitamins and minerals.”

In spite of the potential benefits touted by both amateur enthusiasts and medical professionals, Diaz maintains that if people want to go on the keto diet solely to lose weight, they should consider other options.

“Weight loss shouldn’t be achieved by restricting certain foods, because we do need all foods to play in a whole balanced diet,” says Diaz. “I’m not a huge advocate of the ketogenic diet.”

Terence Cawley can be reached at terence.cawley@globe.com. Follow him on Twitter @terence_cawley