In recent years, the ketogenic diet has increased in popularity. You may have heard about the keto diet from magazine spreads, friends, or from colleagues, which leaves you wondering, “How does the keto diet work, exactly?”
Dietitians, nutritionists, and the mainstream media have taught people that fat, particularly saturated fat, is bad for your health. They preached about high-carb, low-fat diets, believing that a high-fat diet would lead to heart disease, high blood pressure, high cholesterol levels, and other health risks. However, new research shows that these teachings are a complete myth[*].
In fact, a low-carbohydrate, high-fat diet can be very beneficial to your health. Below, you’ll learn the basics of the keto diet, the health benefits associated with ketosis, how the keto diet can lead to weight loss, and how to know if you’re in a ketogenic state.
How Does the Keto Diet Work?
The keto diet is a high-fat, low carb diet. The goal of the keto diet is to enter a state of ketosis, where your body burns ketone bodies — rather than glucose — for energy. But how does the keto diet work, and how do you enter a ketogenic state? Keep reading.
The standard American diet and most Western diets are heavily concentrated in carbs, with some protein, and hardly any fat. When the average person eats a meal rich in carbs, their body takes those carbs and converts them to glucose for fuel. Insulin then moves that glucose into the cell. Glucose is the body’s primary source of energy when carbohydrates are present.
However, things are different on keto. On the ketogenic diet, your carbohydrate intake is kept very low — so when those carbs aren’t present, your body must use another form of energy to keep things ticking.
That’s where fats come in. In the absence of carbs, the liver takes fatty acids in the body and converts them to ketone bodies, also known as ketones, as an energy source. This process is known as ketosis, and it’s the goal for those on a ketogenic diet.
Three ketones are made when fatty acids are broken down:
- Acetoacetate (AcAc): created first during ketosis
- Beta-hydroxybutyric acid (BHB): formed from acetoacetate
- Acetone: created spontaneously[*] as a side product of acetoacetate
Health Benefits of the Keto Diet
The original purpose of the ketogenic diet was to prevent epilepsy in children. But since then, it’s been used for all sorts of reasons. Some of the best and most popular benefits of the ketogenic diet include:
- Better sleep patterns, and fewer feelings of restlessness and fatigue[*][*]
- Satiety, or feeling more full and satisfied during and after meals, which can thereby lead to weight loss][*]
- Heightened mental clarity, allowing you to focus for longer durations[*][*]
- Fat loss, or losing body fat while preserving muscle mass[*]
What to Eat on the Keto Diet
Keto means eating a lot of fat. On the keto diet, the vast majority of your calories will come from fat, with some protein and very few carbohydrates. For most people, the macronutrient breakdown on keto diet looks something like this:
- 70-80% of your calories will come from fat
- 20-25% of your calories from protein
- 5-10% of your calories from carbohydrates
Those used to eating low-carb already might find they need to eat even less dietary carbs to achieve a healthy state of ketosis.
On a keto meal plan, you will eat high-fat foods including avocado, coconut oil, olive oil, MCT oil, and nuts and seeds. You will also eat high-quality, grass-fed meats, seafood, eggs, and high-quality full-fat dairy.
You’ll get fiber, vitamins and minerals from leafy green and other keto-friendly veggies such as kale, cauliflower, Brussels sprouts, and spinach.
On keto, you’ll want to avoid grains (even whole grains), starch, and sugar at all costs — as a good rule of thumb, only eat vegetables with fewer than 10 grams of carbs (or roughly 5 grams of net carbs) per serving. Overall, your eating plan should aim to limit your carb intake to less than 30 grams of carbs per day.
One final note: On keto, do not restrict your calorie intake. This is one of the biggest mistakes on keto, where people do not get enough calories after cutting out carbs and sugar.
Why You Don’t Need to Watch Your Protein Intake
Contrary to what some people might think, you don’t need to worry about eating too much protein on the keto diet — it won’t kick you out ketosis.
Your body has a metabolic process called gluconeogenesis (GNG), which is often misunderstood. Some sources claim that eating too much protein will activate GNG and elevate your blood sugar, but that’s a myth.
Here’s the truth:
GNG is in charge of making glucose from non-carb sources, including protein, lactate, and glycerol[*]. This is a normal process crucial for:
- Fueling the few tissues that can’t use ketones, such as part of your brain, red blood cells, and testicles
- Maintaining proper blood glucose levels
- Building glycogen
Without gluconeogenesis, ketosis wouldn’t be possible. Ketones are an excellent fuel source, but since they can’t fuel 100% of your tissues, GNG steps in to fuel the rest.
GNG is also a highly stable mechanism, so even if you eat more protein than the standard keto macros allow, you won’t increase the rate of GNG enough to get kicked out of ketosis.
Watch this video to learn more about protein on keto:
How to Become Fat Adapted
Ketosis is a natural function of the body. In the most extreme measures, it happens if the body goes long periods without food.
In fact, many of you naturally enter ketosis by the time you wake up in the morning, after your body has gone 10–12 hours without food (since dinnertime the evening before). Those in keto are, in a sense, “starving” the body of carbs to condition the body to turn to fat for fuel.
When you’re first adapting your body to run on ketones, you can experience some negative side effects. These include flu-like symptoms known as keto flu, which can include brain fog, mild nausea, headaches, and feeling lethargic. But as you stick with it, your body begins to prefer fat as energy and becomes keto-adapted.
So, how do you make sure your ketogenic diet is “working” and you’re maintaining a state of ketosis? By checking your ketone levels — frequently.
How to Make Sure You’re in Ketosis
Testing ketone levels in your body is the only true way to know whether or not you’ve entered (and remain in) ketosis. This is important to ensure you’re reaping the full benefits of the ketogenic diet.
When your body starts burning fat for fuel and enters ketosis, the blood ketones it creates will spill over into your urine, blood, and breath. As such, it’s possible to test for them in each area.
There are several methods for testing your ketone levels at home.
You can buy urine strips that indicate your ketone level by color. These can usually be bought at your local drugstore or pharmacy for a low cost.
The downside of urine testing is that they aren’t always reliable, especially if you’ve been in ketosis for a while. When you’re more efficient at using ketones, a lower level of ketones might show up — even if you’re burning through them.
Other factors can affect the reading too, such as hydration and electrolyte levels.
Acetone is the ketone that shows up on the breath, and you can test it using a breath meter.
After purchasing the breath meter, there are no ongoing costs for testing like with urine strips. However, this method isn’t the most reliable and usually shouldn’t be your sole method for testing.
This is the most accurate way to monitor ketone levels. Using a blood glucose meter, you can check ketone levels using a blood strip. Just be warned that this method can be pricey if you test frequently.
For best results, you’ll (ideally) be providing your body with optimal nutrition from rich, healthy fat sources, nutritious protein, and other foods that provide the vitamins and minerals your body needs. See the full ketogenic diet food list so you know what to eat to get keto working for you.
How Does the Keto Diet Work? By Helping You Burn Fat for Energy
The keto diet is a high-fat, low-carb diet. Originally used as a treatment for epilepsy, this diet has been shown to help improve mental clarity, boost energy levels, improve sleep patterns, and lead to rapid weight and fat loss.
The keto diet works by restricting your body of carbohydrates, which is converted to glucose in your body. When your body doesn’t have glucose for energy, it starts burning fat instead. When your body converts fat (which are then turned into ketones) as its primary fuel source, you are in a metabolic state of ketosis, the goal of the keto diet.
While cutting out entire food groups (hello, grains and starch) may sound intimidating at first, it’s a lifestyle that many people find preferable to high-carb diets. For more information on how to get started on keto, view this beginner’s guide.