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, moderate in protein and requires higher-than-average consumption of fat. 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.
There are different types of keto diets, but generally it's recommended that followers break down their macronutrients as follows, according to the Harvard T.H. Chan School of Public Health:
- 70 to 80 percent fat
- 10 to 20 percent protein
- 5 to 10 percent carbohydrates
For someone on a 2,000-calorie diet, that means they're aiming for about 165 grams of fat, 75 grams of protein and 40 grams of carbohydrates each day (for reference, one regular-sized bagel has about 55 grams of carbs, per the USDA).
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?
The diet was originally created as a way to manage treatment-resistant epilepsy. And while there's no long-term research that conclusively shows it's effective for medical conditions outside of seizure control, some preliminary research on keto has found it may hold promise in helping to manage other health problems, including:
There may also be cognitive benefits to ketogenic diets, which were found to improve working memory, visual attention and the ability to switch between tasks in older adults, according to one small, short-term study of 19 people published 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.
There is some promising evidence on the effectiveness of these keto supplements, but the research is still very thin, according to a March 2018 review article in PeerJ.
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 — which include one to two days a week of higher carb intake — 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 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, a 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.
Plus, some research, including a September 2019 study in the European Heart Journal, have found an association between low-carb diets and a higher risk of death.
The keto way of eating can also cause low blood pressure, constipation, kidney stones, nutrient deficiencies and an increased risk of heart disease, according to UChicago Medicine.
Also, keto might not be so heart-healthy or sustainable. A June 2020 study in The American Journal of Medicine notes that a major concern of the keto diet is that it allows eating plenty of saturated fats and animal products, which are known to increase risk for heart and kidney diseases as well as cancer. Therefore, the researchers state that this diet is not for people who aren't meticulous and driven to make the right food choices.
First, since research is still limited on the keto diet and it has the potential to cause serious issues, be sure to speak with your doctor to decide if it's a good fit for you.
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, aiming for 2,000 calories and following the typical keto diet, your meals might look something like this:
- Breakfast: 44 grams of fat, 15 grams of protein and 10 grams of carbohydrates
- Lunch: 65 grams of fat, 35 grams of protein and 17 grams of carbohydrates
- Dinner: 56 grams of fat, 25 grams of protein and 13 grams of carbohydrates
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 (AHA). 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 try to avoid eating trans fats, per the Dietary Guidelines for Americans. And the AHA recommends that saturated fats make up only 5 to 6 percent of your daily calories; if you're eating 2,000 calories per day, that amounts to about 13 grams max. This means that the vast majority of fat you consume on the ketogenic diet should come from unsaturated sources.
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.
- Nutrients: "Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence From Animal and Human Studies"
- JAMA: Low-Carbohydrate Diets and Realities of Weight Loss
- Journal of Evolution and Health: "Ketogenic Diets, Caloric Restriction, and Hormones"
- Psychopharmacology: "Effect of a Ketogenic Meal on Cognitive Function in Elderly Adults: Potential for Cognitive Enhancement"
- Exercise and Sport Sciences Reviews: "Ketogenic Diets for Fat Loss and Exercise Performance: Benefits and Safety?"
- Nutrients: "The Effects of a Ketogenic Diet on Exercise Metabolism and Physical Performance in Off-Road Cyclists"
- Indian Journal of Medical Research: "Ketogenic Diets: Boon or Bane?"
- Harvard Health Publishing: "What is keto flu?"
- American Heart Association: "The Facts on Fats"
- Harvard T.H. Chan School of Public Health: "Diet Review: Ketogenic Diet for Weight Loss"
- USDA FoodData Central: "Bagel"
- Neurotherapeutics: "Ketogenic Diets for Adult Neurological Disorders"
- The Journal of Nutrition: "The Ketogenic Diet: Evidence for Optimism but High-Quality Research Needed"
- PeerJ: "The Use of Nutritional Supplements to Induce Ketosis and Reduce Symptoms Associated With Keto-Induction: A Narrative Review"
- Nutrients: "Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies"
- European Heart Journal: "Lower carbohydrate diets and all-cause and cause-specific mortality: a population-based cohort study and pooling of prospective studies"
- UChicago Medicine: "Ketogenic diet: What are the risks?"
- Office of Disease Prevention and Health Promotion: "2015-2020 Dietary Guidelines for Americans"
- American Heart Association: "Saturated Fat"
- The American Journal of Medicine: "From Fad to Fact: Evaluating the Impact of Emerging Diets on the Prevention of Cardiovascular Disease"