"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."
You’re transitioning. Your body is equipped to process a high intake of carbs and a lower intake of fat. Your body needs to create enzymes to be able to do this. In the transitional period, the brain may run low on energy which can lead to grogginess, nausea, and headaches. If you’re having a large problem with this, you can choose to reduce carb intake gradually.
For those looking for something just a little closer to real sugar, you can use Xylitol. It cooks and tastes very similar to sugar, but it has a slight glycemic impact (13 vs. 100 for sugar). It is great, but please keep in mind that it is very toxic to animals and it will raise insulin levels slightly. These are the two most cited reasons for not using Xylitol.
A systematic review in 2018 looked at 16 studies on the ketogenic diet in adults. It concluded that the treatment was becoming more popular for that group of patients, that the efficacy in adults was similar to children, the side effects relatively mild. However, many patients gave up with the diet, for various reasons, and the quality of evidence was inferior to studies on children. Health issues include high levels of low-density lipoprotein, high total cholesterol, and weight loss.
Aude, Y., A. S, Agatston, F. Lopez-Jimenez, et al. “The National Cholesterol Education Program Diet vs a Diet Lower in Carbohydrates and Higher in Protein and Monounsaturated Fat: A Randomized Trial.” JAMA Internal Medicine 164, no. 19 (2004): 2141–46. doi: 10.1001/archinte.164.19.2141. jamanetwork.com/journals/jamainternalmedicine/article-abstract/217514.
Avocados are loaded with heart-healthy monounsaturated fats, as well as fiber, which keeps your digestion running smoothly. This fruit can also help replenish electrolytes in the body. For example, a cup of avocado delivers 975 milligrams of potassium, a mineral that regulates fluid balance in the body. That’s extra important when you're on a very low-carb diet—this type of eating causes your body to excrete water and electrolytes, which can lead to dehydration, dizziness, and fainting.