Ketosis and the Ketogenic Diet Explained – A Complete Beginners Guide
By: Alison Moodie
- The ketogenic diet is a high-fat, low-carb eating plan that causes your body to burn fat, and not glucose, for energy.
- The diet is made up of mostly fats (75 percent of your daily calories), some protein (20 percent) and a small amount of carbs (5 percent)
- Benefits of the diet include weight loss, reduced inflammation, and increased energy.
- The first two weeks of the diet can be tough, and some people experience the keto flu. Typical symptoms are insomnia, brain fog, irritability, nausea, stomach pains, sore throat, chills, and muscle aches.
- You can check if you’re in ketosis using urine, blood or breath measures.
It feels like everyone is talking about the keto diet — the high-fat, low-carb eating plan that promises to turn your body into a fat-burning machine. For that reason, keto has surged in popularity over the past year as a lose-weight-fast strategy. Thank Hollywood A-listers and professional athletes like Halle Berry, Adriana Lima, and Tim Tebow who’ve publicly touted the diet’s benefits, from shedding weight to slowing down aging. Here’s everything you need to know about going keto — and how to do it the Bulletproof way.
How does the ketogenic diet work?
The keto diet changes the way your body converts food into energy. Eating a lot of fat and very few carbs puts you in ketosis, a metabolic state where your body burns fat instead of carbs for fuel. When your body is unable to get glucose from carbs, your liver converts fatty acids from your diet into ketones, an alternative source of energy. Burning ketones in place of glucose reduces inflammation and spurs weight loss.
What are the origins of the keto diet?
The keto diet isn’t new, and it’s been around for nearly a century. It was originally developed to treat people with epilepsy. In the 1920s, researchers found that raised levels of ketones in the blood led to fewer epileptic seizures in patients. The keto diet is still used today to treat children with epilepsy who don’t respond well to anti-epileptic drugs.
The benefits of the ketogenic diet
- Burns fat: The keto diet often leads to rapid and substantial weight loss. Ketones suppress ghrelin, which is your hunger hormone, and increase cholecystokinin (CCK), which makes you feel full. Reduced appetite means it’s easier to go for longer periods without eating, which encourages your body to dip into its fat stores for energy.
- Increases energy: Ketosis helps the brain create more mitochondria, the power generators within cells. More energy in your cells means more energy for you to get stuff done.
- Reduces inflammation: The keto diet is anti-inflammatory, and could protect you against major degenerative diseases such as Alzheimer’s and cancer. One study found the keto diet can lower inflammation in the brain following injury.
What to expect when going keto
The first two weeks on the diet can be rough, when you may experience what is known as the “keto flu.” The keto flu is your body’s natural response as it adjusts to burning fat, and not sugar, for energy.
Symptoms include: insomnia, brain fog, irritability, nausea, stomach pains, sore throat, chills, and muscle aches.
The keto flu typically sets in at the 24- to 48-hour mark. It generally lasts for a few days, although symptoms can remain for up to one month. Whether you experience symptoms, and their severity, depends on your metabolic flexibility — your body’s ability to adapt to a new fuel source (in this case, fat versus carbs).
Metabolic flexibility is primarily determined by your genes and lifestyle. If you ate a diet high in refined sugar and carbs prior to going keto, you’ll likely experience more severe symptoms.
Related: How to Conquer the Keto Flu
Some people notice a metallic taste in their mouth within the first few days or week of starting the keto diet. This is normal, and a sign that acetone — a form of ketones — has been released in the body, usually in the breath, urine, and sweat. Keto breath is temporary, and usually subsides once your body has adjusted to fewer carbs.
As your body adapts to using fat as fuel, your symptoms should ease off and you’ll start to feel better than before you started. If you still experience flu symptoms, permanent ketosis may not be right for your body, and you might might want to try cyclical ketosis, where you eat slightly more carbs one day a week.
What to eat on a ketogenic diet
The diet is made up of mostly fats (75 percent of your daily calories), some protein (20 percent) and a small amount of carbs (5 percent). Choose low-carb foods such as meat, fish, eggs, vegetables, and smart fats. Take a look at the Bulletproof Diet Roadmap to make sure your keto diet is also Bulletproof-approved.
Vegetables: If it’s green and leafy, it’s probably keto-friendly. Stick to vegetables that grow above the ground, such as broccoli, asparagus, cucumbers and zucchini. Root vegetables like sweet potatoes, carrots, and parsnips tend to be higher in starch, so eat those in moderation.
Keep it Bulletproof: Lightly cook cruciferous and leafy greens like spinach and kale to reduce their oxalate content. Oxalates can prevent your body from absorbing minerals such as calcium. Limit nightshades– they can cause inflammation in sensitive people.
Protein: Keep in mind that keto is high-fat, and not high-protein, so you don’t need to eat very much meat. Too much protein turns into glucose in the body, making it harder to stay in ketosis. Stick to fatty cuts of grass-fed, pasture-raised, or wild meat, and wild-caught fish. Red meats, offal/organ meats, pork, eggs (preferably pastured), fish, shellfish, and whey protein concentrate.
Keep it Bulletproof: Avoid nut butters and soy. Limit poultry like chicken and turkey.
Dairy: Stick with organic and grass-fed dairy — it’s full of anti-inflammatory fats like omega-3s and conjugated linoleic acid. All full-fat butter, ghee, cheese, yoghurt, sour cream, and heavy cream are on the menu.
Keep it Bulletproof: Skip the cheese and opt for raw, full-fat, unpasteurized dairy where you can.
Oils and fats: Most calories on the keto diet come from fats, so load up. Choose saturated and monounsaturated fats like butter, lard, and ghee, along with coconut oil, fish oil, and medium-chain triglyceride (MCT) oil. Your daily fat count also comes from egg yolks and fatty meats and seafood.
Keep it Bulletproof: Opt for grass-fed butter and ghee, and avoid canola, cottonseed, corn, flaxseed, peanut, safflower, soy, and sunflower oils.
Fruits: The sugar content in most fruit can take you out of ketosis. Fruit is high in a type of sugar called fructose, which the liver converts into either glucose or triglycerides (a type of fat in the blood). Fresh berries, avocado, and coconut are the exceptions. Lemons and limes can be used sparingly to flavor water.
Keep it Bulletproof: Buy organic fruit where possible.
Nuts, seeds and legumes: Eat these in moderation. While high in fat, most nuts are also high in protein and carbs. Snack on lower carb nuts like pecans, macadamia nuts, and brazil nuts, along with chia, coconut, flax seed, hemp, pumpkin seeds, sesame, and black soybeans.
Keep it Bulletproof: Nuts are the one area where keto and Bulletproof diverge. All nuts and legumes — except for coconut — are labeled as suspect on the Bulletproof Diet. Nuts carry mold toxins and spoil easily once shelled. If you want nuts, buy them raw and keep them refrigerated or frozen.
Beverages: It’s common to become dehydrated on the keto diet. Your insulin levels drop when you restrict carbs, and low insulin makes it harder for your body to retain sodium and water. Drink plenty of plain water, and sip on bone broth to replenish electrolytes, especially during the first couple of weeks when your body is adjusting to the new diet.
Tea and coffee — including Bulletproof Coffee — are ketogenic. The fat and oil in Bulletproof Coffee increase your energy and keep you full for longer.
Keep it Bulletproof: Avoid nut milks, which are often high in mold toxins (the exception is full-fat coconut milk).
Types of ketogenic diets
Standard ketogenic diet: You eat very low carb (less than 50 grams net carbs a day), all the time.
Targeted ketogenic diet: You follow the standard keto diet, but eat extra carbs right before (30 minutes to an hour) a high-intensity workout. The glucose is meant to boost performance, although no scientific studies have linked low blood glucose to reduced weight-lifting performance.
Cyclical ketogenic diet: The Bulletproof Diet falls into this category. You eat high fat, low carb (less than 50 grams of net carbs a day) five to six days of the week. On day seven, you up your carb intake to roughly 150 grams, during what’s called a carb refeed day. Carb cycling this way helps you avoid the negative effects some people experience when they restrict carbs long term, like thyroid issues, fatigue and dry eyes.  Full ketosis isn’t for everyone, and adding carbs such as sweet potatoes, squash, and white rice one day a week keeps your body systems that need some amount of carbs functioning properly.
How to know you’re in ketosis
You’re in ketosis when your ketone levels measure 0.8 (that’s millimoles per liter). You can test your levels using urine sticks, blood sticks, or a blood meter. You can also test for acetone levels in your breath using a breath analyzer.
However, just tracking how your body feels is a simple way to know whether you’ve hit that ketosis sweet spot. Here are signs you’re probably in ketosis:
- Reduced hunger: Ketones suppress your hunger hormones, helping you feel full for longer.
- Keto breath: People often experience a metallic taste in their mouth due to raised ketone levels.
- Weight loss: The keto diet burns fat, so if you’re losing weight, you’re likely in ketosis.
Related: How to Find Your Ideal Carb Intake
Need some inspiration to get started? Check out our simple Bulletproof meal plan with recipes included.
Going keto doesn’t mean you have to forgo comfort foods. Here are some delectable recipes that will satisfy any cravings but keep you in ketosis: