The ketogenic diet continues to be one of the most popular diet plans in the U.S., garnering roughly a million online searches a month. But what is the keto diet? How does it work? And is keto healthy for you?
Many people call it the keto diet, but it's actually short for the ketogenic diet. Overall, the main purpose of the ketogenic diet is to lose weight by eating a low amount of carbs, a high amount of fat and a moderate amount of protein.
So, why is keto so popular? The keto diet didn't make U.S. New & World Report's 2022 list of the best overall diets, but it did come it at No. 4 on their list of best diets for fast weight loss. That's because the keto diet reaps the benefits of ketosis, the metabolic state when your body uses fat for energy. Some methods to measure ketosis are better than others, and there are certain foods that can help you achieve ketosis.
The keto diet was first invented in the 1920s as a treatment for epilepsy, but its use declined with the use of modern epilepsy drugs. Since the late '90s, however, it has exploded in popularity as a weight loss strategy, according to the National Library of Medicine.
What is the keto diet?
The ketogenic diet is an eating plan that has very high fat content and little to no carbs. This is because the main purpose of the keto diet is to get your body to burn fat as its main energy course rather than carbohydrates and glucose, a state known as ketosis. This shift in your metabolic state can lead to weight loss. People who support using the keto diet also say that there are many benefits to the keto diet besides losing weight.
What are the basic rules of the keto diet?
The ratio of fat to carbs and protein is 4:1. The standard ketogenic diet is 70% fats, 20% proteins and 10% carbohydrates. The ketogenic diet is meant to send your body into ketosis.
What is ketosis?
The body always seeks out glucose (and its stored form, glycogen) for fuel. Limiting carbohydrates mean limiting the body’s favorite fuel — and so it must adapt.
The alternative solution is to burn stored fat instead. The metabolic shift from burning glucose to fat produces ketones. Ketones are important because while the body is burning fat for energy, the brain doesn’t have the ability to do this. Instead, the brain will fuel on ketones produced by the liver instead. Once the body fuels on fat and the brain fuels on ketones, you are in ketosis.
The keto diet is one in which you drain your liver glycogen stores and force the body to find that alternative fuel. In addition to limiting carbohydrates to achieve this, protein content may also need to be reduced. That’s because protein actually has a small insulin-stimulating effect, which suppresses ketone creation.
What can you eat on the keto diet plan?
In order to achieve ketosis, you must drastically limit the amount of carbohydrates you consume. Some types of fasting can also lead to ketosis. That said, the keto diet doesn't mean you're eating all meat and fatty foods constantly. Working in healthy fats, from avocados to lives, should be central to your keto diet and you should also try to eat vegetables that are not high in starch, as well as nuts, seeds, wild fish that's not high in fat, eggs and chicken for protein. You can also eat coconut oil, dairy with full fat, like hard cheese.
The keto diet can include:
- red meat (fatty and lean)
- full-fat dairy
- eggs, poultry and fish
- butter and oils
- nuts, seeds and avocados
What can't you eat on the keto diet?
Although carbohydrate restriction is central to the diet, studies have found that eating 20-50g of carbohydrates a day can still result in ketosis and weight loss, and may include more plant-based fiber derived from previously eliminated nuts and non-starchy vegetables. This makes the diet less restrictive and more sustainable over time.
Foods to avoid on the keto diet include:
- Bread, rice, pasta and potatoes
- Beans and lentils
- Most fruits and starchy vegetables
Is the keto diet bad for you?
While TODAY's Al Roker has been a big fan of the keto diet, the nutrition plan has its fair share of critics. The reality is that any diet can be made unhealthy. The benefit or harm of the keto diet will depend on the dietary pattern chosen.
Very low-carbohydrate diets that lack sufficient vegetables and other important phytonutrients may harm health in the long term, but a keto plan that includes fiber-rich plants, healthy fats and moderate protein can be beneficial to weight management and reduce and manage chronic disease.
What is keto flu?
Side effects of the keto diet can include constipation, though that can be avoided through consumption of higher fiber foods. Additionally, many individuals will experience what is commonly known as the “keto flu,” unpleasant symptoms that can occur when the body is transitioning from a carb- to fat-burning mode. These are short-term and subside as the body enters ketosis.
Who is a keto diet good for?
Multiple benefits have been associated with the ketogenic diet. A 2021 study comparing a low-fat diet with a ketogenic diet found that the keto participants had more stable blood sugar and insulin levels, despite eating more calories. This is critical, as recent data indicates that unstable blood glucose levels can increase appetite and lead to weight gain.
Another study, published in 2020 assessing low-carb diets in older individuals, found improvements in body composition, fat distribution and metabolic health. The diet may also play a role in reducing inflammation, management of Type 2 diabetes and may even help enhance cancer treatment.
How do you know when your body is in ketosis?
As a dietitian, I often tell my patients you don’t know what you can’t measure. Increased ketone production is a sure sign of ketosis and can be monitored through the breath, blood and urine, but the accuracy of these methods and the frequency of testing vary greatly.
Since ketones change quite a bit, much like blood sugar, it is important to check levels of ketosis as they are impacted by food and exercise, ideally three to five times per day. Urine strips are the least expensive but least accurate. For accuracy, blood ketone meters or a clinically-backed breath ketone device are often the best bet.
Is the keto diet safe?
Studies show that low-carbohydrate diets can be a safe and effective way for people diagnosed with Type 2 diabetes or prediabetes to normalize hemoglobin levels, reduce the risk of hypoglycemia and boost weight loss.
Ketogenic diets, however, are not for everyone and should be avoided by children and teens, people with Type 1 diabetes, pregnant people and individuals with disorders of the kidneys, gall bladder, pancreas and liver. Talking with your physician first and working with a registered dietitian are recommended before starting on the ketogenic diet to reduce risks and improve short-term and long-term success for weight loss and overall health.