By now, you've probably heard about the keto diet and its promise to help you shed pounds quickly. But how much do you really know about this trendy eating approach?
Here, we'll cover the basics, including what the diet really does to your body, the benefits and drawbacks of ketosis, and which keto-based plan might be right for you.
Break It Down: What Is the Keto Diet?
A ketogenic diet is low in carbohydrates and requires higher-than-average consumption of fat and protein. This type of eating style has become increasingly popular for weight loss in recent years, but it has been studied and used clinically for the treatment of epilepsy since the 1920s, according to a September 2018 article in the Indian Journal of Medical Research (IJMR).
Keto diets differ from other low-carbohydrate plans because followers consume only 20 to 50 grams of carbs per day. This extremely low amount induces ketosis, a physiological mechanism that occurs only when the body has insufficient glucose (sugar) to convert into energy and must use fat instead.
Read more: Signs That You Are in Low-Carb Ketosis
While the basics are the same, there are actually four main variations of the keto diet, according to the IJMR article:
- The standard ketogenic diet (SKD): SKD is a very low-carbohydrate diet that involves moderate protein consumption and high quantities of fat. Typical ratios for this diet are 10 percent carbohydrate, 20 percent protein and 70 percent fat.
- The cyclical ketogenic diet (CKD): CKD is a standard ketogenic diet that involves periods of higher carbohydrate consumption. Followers of these diets typically adhere to the SKD version five days per week, then take two days during which higher amounts of carbohydrates are consumed.
- The targeted ketogenic diet (TKD): TKD allows followers to add additional carbohydrates based on periods of intense physical exertion.
- The high-protein ketogenic diet (HPKD): HPKD involves higher consumption of protein compared to the SKD. Typical ratios for this diet are 5 percent carbohydrate, 35 percent protein and 60 percent fat — so essentially, fewer carbs and less fat than the SKD.
The type of keto diet someone chooses may depend on their medical issues, weight-loss goals, athletic performance goals or other factors. In general, though, a keto diet is followed only over short-term periods for fat-reduction and muscle-building purposes. Only those with certain medical conditions typically need to continue a keto diet in the long-term.
So, What's the Hype All About?
Although the diet was originally created as a way to manage treatment-resistant epilepsy, keto has since been shown to also help manage a variety of health problems, including:
In addition to these beneficial effects, keto can be used to modify hormonal and metabolic responses in the body, per a June 2014 study in Nutrients. Altering these responses has clinically useful effects in disease management, and may also improve athletic performance and promote weight loss and muscle building in healthy individuals, says an article in the July 2015 issue of Exercise and Sport Science Reviews.
There also seem to be cognitive benefits to ketogenic diets, which have been shown to improve working memory, visual attention and the ability to switch between tasks in older adults, according to a study published in October 2016 in Psychopharmacology.
Many of the benefits of the keto diet are attributed to ketosis. Because ketosis is marked by elevated levels of ketones (molecules produced when the body burns its own fat), alternative methods of raising ketone levels and producing ketosis have been attempted. However, ketone supplements that supposedly induce ketosis do not result in the same benefits as adherence to the diet, according to a January 2017 review in the Journal of Special Operations Medicine.
Why ketosis induces so many positive effects is not fully understood. It may act as a stressor, mimicking starvation, suggests a June 2018 article in the Journal of Evolution and Health. However, the keto diet does provide the body with adequate nutrition for survival, per the June 2014 study in Nutrients.
Disadvantages of the Keto Diet
Despite the purported benefits, the ketogenic diet has a few disadvantages:
1. It's very strict. Keto can be difficult to follow, especially for long periods of time. The high fat content of the diet can make it particularly difficult. Making sure that you're consuming primarily healthy fats (like the healthy omega-3s found in fatty fish) and not just saturated fats can also be challenging.
2. Ketosis may come with side effects. Entering ketosis can initially be unpleasant and may trigger a range of side effects (more on that in a minute).
3. It's easy to fall out of ketosis. This is one of the main reasons that cyclical ketogenic diets are becoming increasingly popular: They offer many of the benefits of ketosis while allowing you to maintain a balanced lifestyle. Essentially, they allow you to incorporate the foods you typically avoid, which is important for long-term diet adherence from both a nutritional and psychological perspective.
Short-Term Negatives of Ketosis
Short-term adherence to any form of keto has few long-term negative health effects for most people. The vast majority of people find that the primary negative to ketogenic diets and ketosis is how your body reacts to the elimination of carbohydrates. This is commonly known as "keto flu."
The phenomenon of "keto flu" is essentially your body's response to the combination of carbohydrate withdrawal and electrolyte imbalance that typically occur when your body first enters ketosis, according to Harvard Health Publishing. Most people experience an array of gastrointestinal symptoms and flu-like symptoms, including:
- Body aches and pains
- Bad breath
- Changes in bowel habits
- Vomiting and other forms of gastrointestinal discomfort
- Electrolyte imbalance and dehydration
Managing your electrolyte levels and staying hydrated can help mediate these side effects. Because "keto flu" lasts only about a week or two as you adjust to ketogenic diet foods and ketosis, it's not considered a serious side effect of the diet. Long-term negatives of the ketogenic diet and ketosis are more relevant to people with specific medical conditions, like type 2 diabetes and epilepsy.
Long-Term Negatives of Ketosis
People who adhere to ketogenic diets for clinical reasons may have more serious side effects because they stay on these restrictive eating plans for long periods of time. Indeed, the May 2017 review in Nutrients found that it is possible to develop conditions such as nonalcoholic fatty liver disease and insulin resistance if you maintain the diet for too long.
The keto way of eating was originally designed for children who were unresponsive to epilepsy medications — which means that some people can grow up adhering primarily to this diet. However, it has the potential to cause poor growth, kidney stones, liver problems, heart problems, nutrient deficiencies (specifically for vitamin D and trace minerals) and other issues in young people.
Entering ketosis can be challenging. The easiest way to induce it quickly is by eliminating as many carbs as possible. Many people also choose to fast to induce ketosis more rapidly. However, a gradual introduction is often better tolerated as it is associated with fewer side effects.
Staying in ketosis requires adherence to low-carbohydrate, high-fat diet proportions. Most people who adhere to ketogenic diets distribute their fats, proteins and carbohydrates in a way that helps them maintain a feeling of fullness throughout the day. Assuming you're consuming three meals a day and following the typical SKD 70-20-10 diet, you should eat:
- Breakfast: 49 grams of fat, 12 grams of protein and 6 grams of carbohydrates
- Lunch: 70 grams of fat, 21 grams of protein and 11 grams of carbohydrates
- Dinner: 61 grams of fat, 19 grams of protein and 9 grams of carbohydrates
As long as you follow the dietary guidelines, you should be able to maintain ketosis.
Eating Keto, the Healthy Way
The most challenging part of trying to enter ketosis is identifying appropriate, keto-friendly foods: incorporating high-fat foods, like fatty fish, and eliminating carbohydrate-rich foods, like grains and fruits. Also, adhering to the correct macronutrient ratios can be challenging due to the high-fat content.
Of course, there's a catch here that makes things more complicated: High intakes of certain types of fat may be bad for your health, according to the American Heart Association. The solution? Aim to limit the amount of trans fat and saturated fat you're eating, while increasing your levels of healthy fats in order to maintain both ketosis and a healthy lifestyle.
Most adults should limit their trans fats to 5 grams per day and should only consume between 20 and 30 grams of saturated fats per day. This means that your healthy ketogenic diet should include about 35 to 45 grams of healthy, unsaturated fats each day.
Foods rich in saturated fats include fatty cuts of meat, milk products and coconut oil. In contrast, healthy mono- and polyunsaturated fats can be found in products like nuts, seeds, avocados, salmon, mackerel and herring.
Incorporating healthy fats into your diet can help you adhere to the ketogenic diet's strict dietary ratios while still maintaining a healthy diet.
Read more: Foods to Eat While on a Ketogenic Diet