Take me and my friend for example. For me, restricting carbohydrates for only 20 hours causes keto flu symptoms, and it sticks around for weeks. However, my friend is able to go from eating a high carbohydrate diet to fasting from all food for days, and he feels better than before. While I am laying in bed fantasizing about cuddling up with baked potato, my friend is finishing his third project. Why the difference?
"Plenty of people jump right in, thinking all they have to do is cut carbs and increase fat. All of a sudden, they hit a wall and get 'keto flu.' They feel tired, lethargic, and experience headaches," Wittrock says. "The primary reason they get these symptoms is lack of the three primary electrolytes: sodium, potassium, and magnesium. If you're deficient in any of these, you'll suffer mentally and physically. This is the single biggest reason people fail on the keto diet."
First, a little background: Eric Westman, MD, director of the Duke Lifestyle Medical Clinic, explained to Health in a previous interview that in order to successfully follow the keto diet, you need to eat moderate amounts of protein, reduce your carb intake, and increase fats. When you reduce your carb consumption, your body turns to stored fat as its new fuel source—a process called ketosis. To stay in ketosis, followers of the keto diet must limit their carbs to 50 grams a day, Dr. Westman says.
Magnesium is another important mineral that can make your transition to ketosis much easier. Although you won’t lose much magnesium while you are restricting carbohydrates, it is essential for helping you prevent and treat cramps, improve sleep quality, and increase insulin sensitivity. To get a decent dose of magnesium, make sure you add some pumpkin seeds, almonds, and spinach to your keto diet.
Wondering what fits into a keto diet — and what doesn’t? “It’s so important to know what foods you’ll be eating before you start, and how to incorporate more fats into your diet,” says Kristen Mancinelli, RD, author of The Ketogenic Diet: A Scientifically Proven Approach to Fast, Healthy Weight Loss, who is based in New York City. We asked her for some guidelines.