Keto diet side effects: What to expect
The ketogenic diet, or keto diet, strictly limits carbohydrates while increasing the amount of fat that a person eats. A common short-term side effect of the keto diet is keto flu, which includes symptoms such as tiredness, nausea, and headaches.
What is the keto diet?
The keto diet limits a person’s daily carbohydrate intake while increasing the amount of fat. The aim is to encourage the body to burn fat for energy instead of carbohydrates.
This metabolic change puts the body into a state of ketosis. Ketosis occurs when the body starts to break down fat due to a lack of blood sugar circulating the body. The body turns the fat into ketones, which provide it with energy.
It takes about 2–4 days for a person to reach the state of ketosis after starting the diet.
Many people begin the keto diet because they wish to lose weight. However, others use it to help manage certain health conditions, such as diabetes.
Most keto diet plans limit the daily carbohydrate intake to 50 grams (g) or less. They also require people to stick to the following nutrient ratiosTrusted Source, based on a daily intake of 2,000 calories:
55–60% calories from fat
30–35% calories from protein
5–10% calories from carbohydrates
The keto diet is a drastic change for many people. According to the 2015–2020 Dietary Guidelines for AmericansTrusted Source, more than half of the population of the United States eat at least the recommended amount of total grains each day, and about 70% eat more than the recommended amount of added sugars each day.
As a result, a sudden change to a low carbohydrate diet may cause side effects for some people. While transitioning into ketosis, people may experience “keto flu.” Common symptomsTrusted Source of keto flu include:
nausea and vomiting
endurance issues when exercising
For most people, keto flu is a short-term side effect that should improve within a few days to a few weeks. Drinking enough fluids and electrolytes may help ease the symptoms. If they do not improve, a person should speak to their doctor.
Long-term health risks
Researchers do not know muchTrusted Source about the long-term effects of the keto diet beyond the first 2 years. However, the potential risks of any restrictive diet include vitamin or mineral deficiencies.
A person on the keto diet needs to monitor their carbohydrate intake from all potential sources, including fruits, vegetables, and whole grains. As a result, they may need to cut back on foods that previously provided them with beneficial nutrients.
Vitamin and mineral deficiencies can cause a variety of symptoms, ranging from mild to severe. A person following the keto diet will need to ensure that they do not miss out on any nutrients as a result of changing their diet.
Other potential risks of a high fat, high protein diet include:
hepatic steatosis (fatty liver)
hypoproteinemia, or low levels of protein in the blood
Low carbohydrate diets, in general, may have adverse effects. For example, a 2016 studyTrusted Source found that people following low carb diets have higher levels of low-density lipoprotein cholesterol, which is a risk factor for heart disease.
Additionally, the authors of a 2012 reviewTrusted Source concluded that a low carbohydrate diet that focused on animal sources of protein and fat increased the risk of type 2 diabetes and death.
Scientists will need to conduct more studies to understand the potential long-term side effects and risks of the keto diet specifically.
The keto diet has some other limitations that a person may wish to consider before they try it, such as:
Varying results: In terms of weight loss, the keto diet may work more effectively for some people than others. According to the Academy of Nutrition and Dietetics, the rate at which people get into ketosis and start losing fat varies depending on several factors. Therefore, the diet will affect individuals differently.
Difficult to follow: The keto diet strictly limits what a person can eat. As a result, it may be challenging to follow the diet for an extended period. If a person stops limiting carbohydrates, they may regain any weight that they had lost.
Saturated fat: As a person can remain in ketosis regardless of the type of fat that they consume, this may lead to a heavy reliance on animal fats or saturated fats, which have associated long-term health risksTrusted Source.
People can reduce the potential risks of the keto diet by:
ensuring that they get enough vitamins and minerals from their food
eating more healthful fats, such as olive oil, oily fish, and avocados, than saturated fats
avoiding processed foods that contain saturated fat
reintroducing some carbohydrates slowly once they reach a moderate weight, if weight loss is their goal
Who should try the keto diet?
The keto diet may be an effective way for some people to manage their weight. This eating pattern may also improve certain health conditions.
For instance, the National Center for Health Research note that the diet may help reduce the frequency of seizures in children with epilepsy, as well as controlling insulin levels and improving insulin sensitivity for people with diabetes.
However, people with other health conditions should not follow the keto diet or should discuss it with a doctor first. According to the Academy of Nutrition and Dietetics, these people include those living with the following conditions:
gallbladder disease or removal
a history of eating disorders
If a person wishes to try the keto diet, they should consider discussing their diet plan with a registered dietitian to determine whether it is the right option for them.