Food & Drink

The Pros and Cons of the Keto Diet, Explained

The keto diet is both extremely restrictive and extremely popular. We help you weigh the pros and cons of trying it out.

avocados
Cole Saladino/Thrillist

The alluring promise of the keto diet, potentially filled with as much bacon, butter, eggs, and avocado as you can eat, sounds like the grown-up version of scoring a golden ticket to Willy Wonka’s Chocolate Factory. I mean, who wouldn’t want to chow down on bacon and butter at every meal? Especially if you ended up dropping a few pounds along the way?

The catch, of course, is that if it sounds too good to be true, it probably is. And that’s exactly what hopeful dieters need to keep in mind when approaching the ketogenic diet (if we're calling it by its formal name). It’s not that this high-fat, moderate-protein, low-carbohydrate approach to eating can’t deliver weight loss in a delicious package, but it’s a restrictive, sometimes complicated affair that isn’t sustainable for most people.

The basic science behind the keto diet

To understand what the keto diet is, you have to understand a little about how your body generates and uses energy for daily activity. All day, every day, your body undertakes a series of chemical processes (together referred to as metabolism) to break down and use a combination of carbohydrates and fats to produce energy. The energy produced is used for everything -- from breathing to brushing your teeth to running to catch a taxi. Your body is burning fuel constantly just to sustain basic life function. And while your body is always burning a combination of fats and carbohydrates, your brain’s primary fuel source is carbohydrates… and your brain requires a surprising amount of energy to get you through each day.

When carbohydrate consumption is limited, your body has to use an alternate fuel source to keep your brain going. This is the general premise behind the ketogenic diet. “The ketogenic diet is a high fat diet with low carbohydrate and moderate protein content,” says Gabrielle Mancella, a Registered Dietitian with Orlando Health. “Carbohydrate is depleted to provide an alternative fuel source, known as ketones, to the brain. The body converts from burning carbohydrates to burning fats, known as ketosis.”

The catch? The extreme nature of the carbohydrate restriction required to enter ketosis. Mancella explains that the traditional ketogenic diet consists of a daily calorie intake of roughly 90% fat, 6% protein, and 4% carbohydrate, while a slightly more moderate approach to the diet might consist of 80% fat, 15% protein, and 4% carbohydrate.

In either case, think about that for a second: Mancella says a 4% carbohydrate consumption translates to roughly 20-50 grams of carbs per day. And given that a single cup of cooked pasta contains roughly 45-grams of carbs by itself, and a single English muffin has about 30-grams of carbs, a single, poorly-planned meal could undo your efforts to achieve and maintain ketosis in a hurry.

And that’s the kicker -- most people “going keto,” may not actually be following a true ketogenic diet since it’s hard to know for sure if your body’s in ketosis. Mancella explains that the only formal and valid method of determining if your body is in ketosis is if there are ketone bodies being excreted in your urine. “There are strips for purchase at local drug stores that are available to determine this,” she says. “Otherwise, we’re not actually sure if we’re in ketosis, and we’re just following a ‘low carbohydrate’ diet.”

eggs
Drew Swantak/Thrillist

The benefits of going keto

The good news is, if you’re a generally healthy adult, you can probably tolerate the keto diet. “It’s likely appropriate and safe for almost everyone,” says Robert Santos-Prowse, a Clinical Dietitian and the author of The Ketogenic Mediterranean Diet and The Cyclical Ketogenic Diet. “Ketosis is a natural metabolic state that everyone has spent some time in at some point in their lives. It has been proven to be most useful for weight loss and diabetes management, but it could provide benefit for some athletes and also might prove to be useful for many disease states including some cancers and forms of neurodegeneration.”

In fact, the diet first gained popularity in the 1920s when it was discovered to have benefits for children suffering from extreme epilepsy. Now, researchers are conducting studies to determine whether it could have benefits for any number of disorders, including the treatment of ALS, Alzheimer’s disease, brain tumors, traumatic brain injury, diabetes, weight loss, polycystic ovary syndrome, glaucoma, Parkinson’s disease, narcolepsy, and some cancers.

It’s important to note, however, that most of the research is being done on diseases and disorders, not specifically weight loss. That doesn’t mean there hasn’t been evidence of weight loss as a benefit of the eating pattern, just that the studies performed specifically for the benefits for long-term weight loss are limited. There’s anecdotal evidence out there, of course, but there was evidence of weight loss associated with a low-fat diet in the '90s… until that farce came falling down around our collective shoulders as the long-term evidence came rolling in to the contrary.

In other words, trying the keto diet specifically for weight loss purposes probably won’t hurt you (although there are a few caveats), but you should probably have a plan for implementing a well-balanced, more sustainable eating pattern that you can stick to indefinitely once you’ve achieved the weight loss you’re looking for.

The dangers and drawbacks of going keto

The primary drawback of keto for the general population is how restrictive the diet is. “It requires more thought than some other diets,” Santos-Prowse says. And whenever a diet requires too much thought or effort, the likelihood of effectively sticking with it becomes diminished. People just don’t like having to think about how, when, and where to get their next meal when they’re so used to grabbing something quick from the nearest fast food joint.

But more than that, people just don’t like giving up carbs. Dr. Kevin Fontaine, a Professor of Health Behavior at the University of Alabama at Birmingham School of Public Health and an expert on the ketogenic diet points to this as one of the main drawbacks of the diet. “Many people find it very difficult to give up carbs, and may be unwilling to do it. Plus, if you’re on the diet and eat a few carbs, you feel physically terrible. It’s hard to stick with this diet, especially while traveling.”

But beyond the general difficulty of following the diet long-term, there are some legitimate concerns for overall health, especially in certain populations. First, all three of the experts interviewed for this article cited the very real possibility for vitamin and mineral deficiencies if supplementation and precaution aren’t undertaken.

“If not done right, this diet can cause havoc on our bodies,” says Mancella. “As a society, we’ve turned to a culture of restriction and extremes in order to obtain unrealistic beauty and aesthetic standards without considering the long-term consequences. This diet doesn’t only affect metabolism, but also every other component of our bodies. By introducing potential vitamin and mineral deficiencies, we’re possibly trading the present moment for quality ones in the future.”
Also, diabetics should not undertake the diet without medical supervision. “Trying a ketogenic diet has the power to drastically and quickly lower blood glucose levels,” says Santos-Prowse. “If a person with diabetes is taking blood glucose-lowering medications, their doctor needs to be on board to help with adjusting or stopping the medications as needed.”

Finally, while it's something of an understudied phenomenon, some people who embark on a keto diet experience a bout of flu-like symptoms (often referred to colloquially as "keto flu"), as your body deals with the shift from crabs to fats as a primary fuel source.  “This has to do with fluid regulation when starting out. As your body adapts to running on fat, you excrete more sodium which makes you feel run down. Increasing fluid and salt intake generally help with this,” Fontaine says.

Should you try a keto diet?

If you’re a generally healthy adult who’s looking for a new way to eat, it’s probably fine for you to try the diet. Just think carefully about your motives, intentions, and long-term plans. Any diet you follow for a short period of time might garner some initial results, but if you’re not intentional about switching to a sustainable, long-term healthy eating pattern, the benefits you see while going keto are likely to be short-lived. Be honest with yourself about whether or not you have the self-control and desire to follow such a restrictive eating pattern. If you don’t, that’s OK. The best diets are those you can legitimately sustain for a lifetime. Restriction isn’t always the best answer.

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Laura Williams is a freelance health writer with a master’s degree in exercise science. She hasn’t followed a “real” diet a single day in her life. Follow her on Instagram and Twitter at @lwilliams_exss.