Pros and Cons of a Keto Diet

Written by Mikel Bryant, MS, RDN, CSOWM, LDN. Mikel is a registered dietitian at Mayo Clinic's campus in Jacksonville, Florida. She works in weight management and bariatric surgery. 

Chances are, if you have followed anyone on social media, gone to a gym, or seen any “health” magazine at a grocery store, you have probably heard about the keto diet. You may have heard family members, friends, or even strangers who have tried it and touted the benefits of weight loss, increased satiety, and decreased hunger between meals. But what exactly does this diet entail? Is it truly as good as it sounds?

“Keto” is short for ketogenic, which is a process during which your body uses fat as its primary source of fuel, instead of carbohydrates. Calories on this diet primarily comes from sources of dietary fat, such as butter, oil, some nuts, and moderate amounts of protein-rich foods, such as meat, full-fat cheese, fish, and eggs. Aptly, the keto diet is a form of low-carb diet, which the Academy of Nutrition and Dietetics defines as consumption of less than 20-50 grams of carbohydrates per day. Given this extreme restriction, many find this diet hard to sustain, as it often requires omission of multiple foods including not only grains and legumes, but also most fruit, milk, yogurt, and many types of vegetables. As a result, there is expressed concern for deficiencies of certain micronutrients, including vitamin A, vitamin C, vitamin K, and folate, as well as dietary fiber.

Most research suggests notable outcomes in the first 2-3 weeks of starting the keto diet, with some studies suggesting benefit for as long as 6-12 months. Most people who have tried this diet report initial symptoms of bad breath, headaches, muscle cramps, nausea, and constipation, which can be collectively known as the “keto flu”. Long-term health risks remain unknown at this time. Some specialists recommend restricting the diet to 3-6 months, with a gradual progression to a Mediterranean or plant-based diet. Others recommend avoidance of any overly-restrictive diet or lifestyle change that may be unsustainable long-term.

If you are wondering whether or not to try this diet, it is highly recommended to first discuss this option with a registered dietitian and/or physician with a clinical specialty in nutrition. Populations for which this diet is contraindicated include persons with eating disorders, pancreatic disease, liver conditions, kidney disease, thyroid problems, gallbladder disease or those who have had their gallbladder removed, and any person with a fat-malabsorption disorder. Some initial studies suggest possible short-term benefit for individuals with neurological disorders, overweight, obesity, metabolic disorders, and diabetes; however, additional research is needed before a general recommendation can be made.

Pros:

• Possible short-term weight loss
• Increased awareness of food and nutrient intake
• Possible increased satiety and decreased hunger between meals
• Restrictive nature of diet usually encourages more home-cooked meals

Cons:

• Rapid weight loss might initially come from “water losses” and may not be indicative of true weight loss
• “Keto flu”
• Increased risk of kidney stones, liver disease, and micronutrient deficiencies
• Lack of fiber may lead to constipation
• Concern for long term outcomes of high-fat diets on cardiovascular health
• Lack of research suggesting long term health benefit
• Difficult to sustain restrictive diet, which may lead to weight regain