You’ve likely heard of the latest nutritional rage: the ketogenic—or keto—diet. High in fat and very low in carbs, the keto diet is praised for helping you burn fat fast, while still allowing you to eat things like bacon and butter. Mmmm. But, while a diet consisting of greasy meat sounds tempting, how safe is the keto diet, really?
We asked Abbey Sharp, a registered dietitian and blogger at Abbey’s Kitchen, what the keto diet is, what you can and can’t eat while following it, and what it does to your body. Here’s what beginners should know.
What is the keto diet and how does it work?
“The keto diet is a diet that’s super high in fat (approximately 80 percent of your diet), super low in carbohydrates (less than five percent of your diet), and with moderates amount of protein (15-20 percent of your diet),” Sharp explains. People on the keto diet often fill up on fat until they’re full. Some may even add fat to regular foods or drinks, like putting butter in coffee. (No joke.)
So, what makes the keto diet special, and more importantly, effective? When you eat a balanced diet, your body typically uses glucose from carbs as its fuel. But, on the keto diet, since you’re consuming high amounts of fat (think meat and cheese) and little amounts of carbs (bye, pasta), your body is forced to get its fuel from fat instead. This is a process called ketogenesis.
During ketogenesis, the body begins to break down fat in the form of ketone bodies. These are the compounds that your body uses instead of carbs. This process not only makes fat a usable energy source, but it burns it quickly, too. That’s why the keto diet is popular for folks looking to lose weight.
What can you eat on the keto diet and what’s off limits?
Because the keto diet is fat-heavy, people rely on lots of meat. “Most animal-based proteins like meat, seafood, and chicken are on the diet. As long as there are no added sugars to them,” Sharp says. “Nuts and seeds, cheese, milk, yogurt, and cream are also all fair game.”
Sharp says that the keto diet does allow low-starch veggies like greens, broccoli, mushrooms, and peppers. However, corn, potatoes, yams, parsnips, and other root vegetables are off-limits. When it comes to fruit, small amounts of lower-sugar fruit like “blueberries, blackberries, and raspberries can be enjoyed in moderation,” she says. But, you should avoid fruit like “oranges, grapes, mangoes, apples, pineapple, banana, dried fruit, and juices.”
In case it’s not clear, you should also avoid grains, beans, and legumes on the keto diet. “Finally, absolutely no added sugars should be consumed,” Sharp adds.
Why would someone go on a keto diet? What are some benefits of it?
The keto diet was initially developed in the 1920s to help treat epilepsy, as research has shown that it can reduce seizures. There’s also been research around whether a keto diet helps treat neurological diseases like Alzheimer’s, Parkinson’s, and MS, Sharp says.
Outside of these conditions, Sharp says that there’s some evidence that a keto diet may “decrease bad cholesterol and increase good cholesterol, improve blood sugar levels, and may help manage Type 2 diabetes.” She also says that the keto diet may potentially even be used as a form of therapy for patients with some types of cancers. “We’re still really getting into the research to understand all of its roles,” she explains.
And when it comes to weight loss—which is what many people today use it for—the keto diet does tend to help a lot of people burn fat quickly, Sharp says. “The reason for the rapid weight loss seen in [the keto diet] is often because of a drop in water weight,” Sharp explains. So, while you may see physical results fast, Sharp warns that the weight-loss benefits may not be long-term.
“Research suggests that the difference in weight loss between keto and other diets (ie. low-fat, calorie restricted) is negligible after a year,” she says. “Whether or not this diet is sustainable and will lead to long-term results is still unclear.”
What are the side effects of the keto diet?
When you first embark on the keto diet, you may not feel great. You are, after all, putting your body through a substantial dietary change. Cutting carbs and eating large amounts of fat can cause less-than-desirable symptoms known as the “keto flu.” While temporary, these symptoms can include dizziness, nausea, bloating, headaches, and fatigue. After several days, however, your body should adjust.
Sharp cautions that because the keto diet cuts out important food groups, you could find yourself deficient in some minerals and vitamins. These include “calcium, vitamin D, magnesium, selenium, zinc, and electrolytes.”
Another thing to keep in mind? Going to the bathroom. “I also would be worried about constipation. Many keto dieters do not compensate for the reduced whole grains, and fiber-rich fruits and veggies with more high-fiber vegetables,” she says. “You’ll want to make an extra effort to ensure [that] you’re getting your 25-38 grams of fiber each day.”
Apart from the short-term side effects, Sharp says that there are some bigger concerns to know about if you’re on the keto diet. “There is a concern that a high-fat diet can be problematic for heart health,” she says. “However, the research in this area is mixed… and it depends on the type of fat [that] you are consuming.”
Eating large quantities of fat and meat can also lead to changes in your cholesterol. “Some studies have found that a keto diet may lead to high cholesterol in the long-term. While other studies have found that it lowers the bad cholesterol and increases the good cholesterol,” Sharp says. “Most of these studies are short in length. And it also likely depends on the individual’s susceptibility and history of heart disease. So it’s still unclear what the long-term consequences are for the general population.”
The bottom line
If you do decide to try the keto diet, Sharp suggests the safest way is to reduce the animal protein in your diet (i.e. the sources of saturated fat). Instead, she advises focusing on consuming more unsaturated fats, like avocado, nuts, seeds, and olive oil. She also points out that since everybody is different, listening to your own body and nutritional needs is key.
“The reality is that many of the studies we have on the keto diet are short in length, often because many subjects were unable to follow the diet or were experiencing some of the side effects mentioned,” she says. “If you are going to try out the diet, make sure [that] you meet with a dietitian and/or doctor beforehand to make sure [that] you are meeting all of your nutritional needs to prevent malnutrition.”
“And, if the diet isn’t working well for you, and you find yourself emotionally or physically not feeling yourself, it’s best to get off the diet bandwagon.”