The ketogenic diet is not a benign, holistic or natural treatment for epilepsy; as with any serious medical therapy, there may be complications.[27] These are generally less severe and less frequent than with anticonvulsant medication or surgery.[27] Common but easily treatable short-term side effects include constipation, low-grade acidosis and hypoglycaemia if there is an initial fast. Raised levels of lipids in the blood affect up to 60% of children[37] and cholesterol levels may increase by around 30%.[27] This can be treated by changes to the fat content of the diet, such as from saturated fats towards polyunsaturated fats, and, if persistent, by lowering the ketogenic ratio.[37] Supplements are necessary to counter the dietary deficiency of many micronutrients.[3]

But if no carbs are available, our bodies start burning fat as a primary fuel source and producing ketones in the liver, which the body can turn into energy. This metabolic state, called ketosis, is what happens when someone is starving. But it's also how Harper's body works every day. His system relies on fats like butter, oil, and lard as a primary energy source instead of packing them on as in-case-of-emergency poundage.

I know you’ve been hearing and seeing the keto diet advertised everywhere. Maybe you’re already on the keto diet, but maybe you’re not and have no idea what all the buzz is about. Maybe you’re just doing a low carb diet and that’s working for you. Wherever you are in your health and journey, the keto diet is hot right now and getting a lot of attention and for good reason.


Before we dive further into weight loss, a note: Weight loss isn't for everybody, and neither is following a specific, restrictive eating plan. If your goal is to lose weight, that's fine, but your health matters more than a number on a scale (and if you have a history of disordered eating, you should discuss any plans to change your diet with a doctor first). In addition, successful long-term weight loss is the product of many factors: Your physical activity, how much sleep you get, stress management, and other factors like medical issues and hormones all play an important role. What you eat is just one part of the weight loss puzzle.
And good news for coffee addicts: you can still have your morning cup of joe. You’ll just need to adjust what you stir into it. Switch out flavored creamer for the real deal—full-fat heavy whipping cream, which has only 1 gram of carbs per tablespoon. If you want to give your java a jolt of sweet, stir in a low-carb sweetener that uses sugar alcohols. But if you can skip the sweet, even better. In time, you’ll retrain your palate to not crave a sugary start to the day.

As for how it feels to follow the diet, St. Pierre says it will vary from person to person; as with most diet-related things, whether or not a way of eating works is in the eye of the beholder. He’s seen some people feel fine, but that “some clients have found it causes brain fog and lethargy, decreases their performance, disrupts their regular bowel movements, and makes them feel generally crappy,” he says. Some keto adherents also report having pretty atrocious breath, which might be caused by the presence of acetone, a ketone and byproduct of fat metabolism, in exhaled breath.

But if no carbs are available, our bodies start burning fat as a primary fuel source and producing ketones in the liver, which the body can turn into energy. This metabolic state, called ketosis, is what happens when someone is starving. But it's also how Harper's body works every day. His system relies on fats like butter, oil, and lard as a primary energy source instead of packing them on as in-case-of-emergency poundage.
When some people attempt a ketogenic diet, they experience the “keto flu” during the period of time their bodies are adapting to the diet. This is a period of feeling lightheaded, lethargic, irritable, and unmotivated. “It typically lasts one to three days, and may very well be just the result of dehydration. A drop in insulin can impact renal sodium retention such that sodium and fluids are excreted more readily. This also acts to lower blood pressure,” Goss says.
But people who started following the keto diet noticed weight loss for a few reasons: When you eat carbs, your body retains fluid in order to store carbs for energy (you know, in case it needs it). But when you’re not having much in the carb department, you lose this water weight, says Warren. Also, it's easy to go overboard on carbohydrates—but if you're loading up on fat, it may help curb cravings since it keeps you satisfied.

This means that if you have risk factors for heart disease — such as elevated cholesterol levels, high blood pressure (hypertension), or a strong family history of the disease — you should use caution when following this diet. The diet's heavy reliance on fat, especially saturated fat, can elevate cholesterol levels, further increasing your chances of developing heart disease in the future. (7)


We have solid evidence showing that a ketogenic diet reduces seizures in children, sometimes as effectively as medication. Because of these neuroprotective effects, questions have been raised about the possible benefits for other brain disorders such as Parkinson’s, Alzheimer’s, multiple sclerosis, sleep disorders, autism, and even brain cancer. However, there are no human studies to support recommending ketosis to treat these conditions.
The reason you eat a balanced diet, which includes fruits, vegetables, dairy, protein, grains, legumes, nuts, and seeds, is to get a variety of nutrients your body needs to stay healthy. You can do so on a lower calorie diet *and* successfully lose weight. However, on the keto diet, grains, legumes, and fruit are pretty much eliminated (berries, watermelon, and apples are allowed sparingly). These food groups provide a ton of nutrients including fiber, phytonutrients, and antioxidants like vitamins A and C. Keto dieters are also known to have constipation because of the lack of fiber in their diet. (FYI, here are the supplements you should take if you're on the keto diet.)
The brain is composed of a network of neurons that transmit signals by propagating nerve impulses. The propagation of this impulse from one neuron to another is typically controlled by neurotransmitters, though there are also electrical pathways between some neurons. Neurotransmitters can inhibit impulse firing (primarily done by γ-aminobutyric acid, or GABA) or they can excite the neuron into firing (primarily done by glutamate). A neuron that releases inhibitory neurotransmitters from its terminals is called an inhibitory neuron, while one that releases excitatory neurotransmitters is an excitatory neuron. When the normal balance between inhibition and excitation is significantly disrupted in all or part of the brain, a seizure can occur. The GABA system is an important target for anticonvulsant drugs, since seizures may be discouraged by increasing GABA synthesis, decreasing its breakdown, or enhancing its effect on neurons.[7]
There are several types of the keto diet, but essentially, to achieve a state of ketosis, you have to severely reduce the amount of carbs you eat. (You can use this ketogenic calculator to create a custom food plan.) Data suggest the average American man over age 20 consumes 47.4 percent of his daily calories from carbs, and the average American woman over age 20 consumes 49.6 percent of her daily calories from carbs. (3) But in the classic ketogenic diet, which was originally used for the management of seizure disorders, 80 to 90 percent of calories come from fat, 5 to 15 percent come from protein, and 5 to 10 percent come from carbohydrates.
The main objective of the ketogenic diet is to get the body to start relying primarily on fat for energy. In general, our bodies are predominantly fueled by glucose (also known as blood sugar), which we get from carb-rich foods (bread, cereal, pasta, rice, etc.). The digestive tract breaks these foods down into glucose so it can be converted into adenosine triphosphate (ATP), which is the chemical our bodies can use for energy. But when the body is deprived of carby delights, it finds other ways to make energy, and one way is a process called ketogenesis. During ketogenesis, the body turns to fat for energy; the liver breaks it down into ketones, making it a usable energy source, Amy M. Goss, Ph.D., assistant professor at the University of Alabama at Birmingham’s Nutrition Obesity Research Center, explains to SELF via email.
Symptoms of the keto flu include headache, fatigue, dizziness, sleep problems, heart palpitations, cramps, and diarrhea. These side effects usually lessen and eventually resolve in about two weeks. (2) But to lessen the effects of any discomfort, simply consider slowly transitioning onto a ketogenic diet rather than rushing to change your eating habits. By slowly lowering your carbohydrate intake, while gradually increasing your intake of dietary fat over time, you can transition with less of a negative impact and potentially prevent the keto flu.

Bottom line: If you don't measure and calculate exactly each food and ingredient, you won't be able to get into ketosis or maintain it. And who wants to be sitting around measuring and counting everything? Again, this diet really takes the enjoyment out of cooking and eating. (Related: I Had Keto Meals Delivered to See If Sticking to the Diet Was Any Easier)
Con: Results can vary depending on how much fluid you drink. By drinking more water, you dilute the concentration of ketones in the urine and thus a lower level of ketones will be detected on the strips. The strips don’t show a precise ketone level. Finally, and most importantly, as you become increasingly keto-adapted and your body reabsorbs ketones from the urine, urine strips may become unreliable, even if you’re in ketosis.
For people with diabetes, rapidly rising ketone levels can signal a health crisis that requires immediate medical attention. When there is an absence or not enough of the hormone insulin (or the body is too resistant to insulin to allow it to drive glucose into the cells for energy), the body cannot use glucose for fuel. Insulin helps ferry glucose to our cells and muscles for energy. Instead, in this case, the body resorts to burning stored fat for energy through the process of ketosis, leading to a buildup of ketones in the body.
After about two to seven days of following this eating routine, you go into something called ketosis, or the state your body enters when it doesn't have enough carbs for your cells to use for energy. Then it starts making ketones, or organic compounds that your bod then uses in place of those missing carbs—and oh, it also burns fat for more energy, says Beth Warren, R.D., founder of Beth Warren Nutrition and author of Living A Real Life With Real Food.
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