Few diets have gained as much popularity in recent years as the ketogenic diet.
The popular eating approach, nicknamed the keto diet, involves drastically reducing your carbohydrate intake to put you into a state of ketosis, or the point where your body shifts from using carbs to using fat as a primary fuel source. This shift can happen after just a few days of eating a diet that’s very low in carbs — think: between 20 and 50 grams (g) of carbs per day, depending on the individual — according to a past review. That’s because your central nervous system relies primarily on glucose, which is derived from carbs, to function, and it must find an alternate energy source ASAP.
But before you try the keto diet, you should know what you’re signing up for. “[Keto is] a very high-fat diet, which contains moderate protein, and very, very little carbohydrates,” says Georgie Fear, RDN, the Alberta, Canada–based author of Lean Habits for Lifelong Weight Loss. To reach ketosis, you’ll need to limit your daily carb intake to 20 to 50 g per day.
That’s a lot lower than the current recommended daily allowance, or RDA, of 130 g of carbs per day to meet the average minimum amount of glucose used by the brain, per the National Academies of Sciences, Engineering, and Medicine. And unfortunately, this low-carb allotment can make it tricky to get enough vegetables in your diet, as some vegetables boast a high carb count. As a result, people on keto tend to take in less fiber than usual, which can exacerbate symptoms such as constipation that happen as part of the so-called keto flu, per a study published in Frontiers in Nutrition in March 2020. This period often lasts about two weeks, but tummy trouble can persist long after that if your fiber intake remains low.
This is one reason it’s so important to consult with a registered dietitian and your healthcare team before embarking on a restrictive diet such as keto. They’re likely to advise you to up your fiber intake by adding plenty of gut-friendly produce to your plate when doing keto. Furthermore, certain veggies will provide the vitamins and minerals your body needs to thrive — without knocking you out of ketosis.
One of the reasons keto is attractive is the potential for quick, short-term weight loss, says Leah Kaufman, CDE, RD, owner of Leah Kaufman Nutrition in New York City. You’ll find no shortage of anecdotal evidence by way of before-and-after photos online, but it’s true there is some early research to support the idea that keto can help you whittle your waist. For example, one past meta-analysis suggested one possible reason the keto diet leads to weight loss is that ketosis may suppress appetite, even when you’re restricting calories. And a more recent meta-analysis, published in April 2021 in Trends in Food Science & Technology, noted that the keto diet could help manage obesity, though more high-quality research is necessary to confirm this effect is due to ketosis (and not just calorie restriction). In general, researchers caution that more research is needed to confirm the weight loss effect of the keto diet.
Still, Kaufman warns, “I would use caution if trying to use the keto diet as a sustainable approach.” Many registered dietitians (RDs) will say keto is a three-month diet max, but the aforementioned past review suggested people with obesity may be able to follow keto safely for one year, so long as they’re under the supervision of a physician.
Just manage your expectations. With its restrictive macronutrient requirements, keto is not an easy plan to follow. “If you eat out often, travel, or socialize with your friends at restaurants on a regular basis, it can be borderline-impossible to stay on the keto diet,” Fear says. After all, it’s very easy to go over the daily carb amount allowed on the keto diet — despite being high in potassium, a large banana can pack a whopping 31 g of total carbs, notes the U.S. Department of Agriculture (USDA). (Total carbs are different from net carbs; roughly speaking, net carbs are the number of carbs left over when you subtract the amount of fiber and sugar alcohols in a given food, per Atkins.com. Keto dieters often count these carbs.)
In addition, the keto diet generally isn’t recommended for people with kidney or liver problems, type 1 diabetes, heart disease, or gout; anyone whose gallbladder has been removed; or individuals with a family history of cancer, Fear says. It’s also not recommended for pregnant or breastfeeding women, or people with a history of eating disorders.
Bottom line: If you’re thinking about trying the keto diet, consult your healthcare team first. “A patient should go through a medical assessment to make sure that they are a candidate for something like [keto], and then it should be medically supervised,” Kaufman says.
Once you’ve gotten the all-clear from your doc to start the keto diet, stock your pantry, fridge, or freezer (frozen veggies may retain even more nutrients than fresh veggies, per the Cleveland Clinic) with plenty of delicious veggies. Here are the 12 best vegetables to include in your keto diet plan.