The low-carb, high-fat approach to weight loss is red-hot, but dieters beware: It isn’t for everyone.
You may have noticed that the keto diet is experiencing its heyday, with plenty of promises, success stories, and celebrity endorsements to back it.
But despite how fresh and innovative it seems, the keto diet isn’t really that different from popular diets we’ve seen in the past, says Nathan Myers, M.S., R.D., C.D.N., a clinical dietitian at James J. Peters VA Medical Center in New York City. A close cousin: the Atkins diet of the 1970s.
According to Myers, both diets are high in fat, very low in carbohydrates, with moderate amounts of protein. However, while the Atkins diet runs through four distinct phases that alternate fat and carbohydrate intake, the keto diet requires followers to remain in a consistent low-carb ketogenic state.
Do one search of #keto on Twitter, and it’s pretty clear that a large number of people love this diet. But its critics are just as numerous as its fans, with many people claiming that the eating plan is unsustainable and even dangerous.
Here, we weigh the pros and cons of this ultra-trendy diet.
First Things First: What Is a Ketogenic State?
To answer that question, you’ll need a basic understanding of metabolism. Your body prefers to use carbohydrates (which it converts to glucose) as fuel. In their absence, it metabolizes fat instead. That process creates so-called ketone bodies, which course through your bloodstream and provide energy.
This is not business as usual, Myers says. In fact, the ketogenic state mimics the state of ketosis brought on by starvation.
For most of history, being in a ketogenic state was a reaction to a severe lack of food or the result of living in a difficult environment where carbohydrates were hard to come by. People generally didn’t try to be in a ketogenic state—until modern humans were awash in carbohydrates and trying to lose weight.
In terms of how that translates to the diet itself, to achieve a ketogenic state you have to limit your carb intake dramatically, to less than 50 grams per day. By contrast, although the initial two-week phase of the Atkins diet only allows for less than 20 grams of carbs per day, by the fourth phase the intake of healthy carbs is unlimited.
What You Can (and Can’t) Eat on the Keto Diet
Despite the drastic reduction in carbs, keto diet followers are encouraged to eat as much fat as they want. Sources include the following:
- Meats (beef, pork, chicken, bacon, and so on)
- Low-carb vegetables (including broccoli, asparagus, spinach, kale)
- Full-fat dairy (butter, cheese, cream, full-fat yogurt)
- Fatty fish and seafood (salmon, trout, sardines)
- Healthy fats (including extra-virgin olive oil, avocados, coconut oil)
- Seeds and nuts (almonds, walnuts, sunflower seeds, and so on)
As for a list of foods and ingredients to avoid? It’s pretty arduous. Dieters are instructed to stay away from potatoes, pasta, bread, beer, fruit, chocolate, and sugar.
And the lack of “cheap” carbs to fill out a meal can make the diet more expensive too, says Myers.
“It can be hard to stick with the keto diet long-term, due to inconvenience, cost, and ‘choice fatigue,’” he says. It can also lead to GI issues (most commonly constipation), a reduction in athletic performance (especially high-intensity), and difficulty getting adequate nutrition (Myers recommends taking a multivitamin if you do decide to try the diet).
Another slightly scary side effect: There are reports of some people experiencing flu-like symptoms while on the keto diet.
“That’s likely the result of the body’s reaction to a severe reduction in carbohydrate intake and a shift in metabolic processes,” Myers explains, adding that the switch usually occurs over one to five days. Symptoms may include low energy or fatigue, changes in bowel movement regularity, and headaches.
Are There Benefits to a High-Fat, Low-Carb Diet?
On the plus side, Myers says, some studies suggest significant health benefits with the keto diet.
In fact, it may be able to play a role in countering diabetes and the obesity epidemic. It may also help to suppress seizures, Myers says. And the keto diet has been studied for treating Alzheimer’s, glioblastoma multiforme (a brain cancer), mental illnesses, and metabolic diseases (including diabetes).
But be sure to take the findings with a grain of salt, says Myers. “The research on the keto diet around brain function preservation, diabetes, and weight control is promising,” he explains. “However, this research is preliminary, and at this point, not conclusive from my perspective.”
Myers does see the keto diet as an option for people who have not found success with other approaches, but he cautions that folks who are interested should check with their physician or a registered dietitian first.
Ultimately, Myers isn’t a fan: “At this time, I would not recommend the ketogenic diet for 50-plus adults.”