1. The "keto flu"

Many people report feeling sick (known as keto-flu) when they start ketosis. Symptoms include gastrointestinal distress, vomit, lethargy, and a lot of fatigue. Some doctors estimate that around 25% of those who try a ketogenic diet encounter these symptoms, and fatigue is the most common one. This happens during the transition when your body stops burning sugar for energy since it runs out. However, for many people, these symptoms should go away after some time.

2. Diarrhea

When you begin a ketogenic diet, you will probably find yourself rushing to the bathroom quite often. Just do a search on the internet, yes, you'll find people tweeting about keto diarrhea. One possible cause can be the gallbladder being overwhelmed, which is the organ that creates bile to help break down fat.

According to Dr. Shawn, diarrhea could also be caused by a lack of fiber in the diet. Which happens when you practically eliminate carbs like pasta and whole-grain bread without supplementing it with other foods rich in fiber, like vegetables.

3. Reduced athletic performance

Some athletes even claim that a ketogenic diet improved their performance, but most nutritionists don't buy it. A study featured in the Journal of Sports Medicine and Physical Fitness found that those who spend four days on a ketogenic diet performed worse on running tasks and high-intensity cycling, compared to those who spend four days eating a high-carb diet. When the body is in ketosis, it's in a more acidic state, which could restrict its ability to perform as well.

4. Ketoacidosis

People with type 1 or type 2 diabetes should avoid the keto diet unless they discussed it with their doctor and got permission. A dangerous condition called ketoacidosis can be triggered by ketosis in people with diabetes. This happens as a result of the body storing too many ketones (acids produced as a result of burning fat) causing the blood to become acidic, which could damage the kidneys, liver, and brain.

5. Weight regain

Many health experts consider the keto diet no beneficial in the long-term because it's so restrictive. Most people found that they regained most of the weight they lost once they ended the diet and resumed eating carbs. This problem seems to affect all fad diets, but it's even more common with the keto diet. So if you want to try ketosis because your friend recently lost weight on it, give it some time, he will most likely gain it back.

6. Less muscle mass and decreased metabolism

Another disadvantage of a keto diet is that a lot of the weight you lose can be a loss of muscle mass. This is especially true for those who eat more fat than protein. Your metabolism will also be affected since muscle burns more calories than fat.

"When people stop their ketogenic diet and regain most of their lost weight, it's usually not in the same proportions," says Shawn. You're more likely to regain fat than lean muscle. Which means you're back to the starting weight without the muscles mass to burn calories.

7. Increased risk of diabetes and heart disease

When done under the guidance of a doctor or nutritionist, you will minimize the risks associated with a keto diet. But trying to do it without the guidance, such high-fat diets can raise cholesterol levels and increase the risk of getting diabetes. It's even become to be known as a "cardiologist's nightmare." The European Society of Cardiology just recently presented a 25,000-person study which found that people on low-carb diets have the greatest risk of dying from cardiovascular conditions and cancer.