The keto diet emphasizes weight loss through fat-burning. The goal is to quickly lose weight and ultimately feel fuller with fewer cravings, while boosting your mood, mental focus and energy. According to keto proponents, by slashing the carbs you consume and instead filling up on fats, you safely enter a state of ketosis. That’s when the body breaks down both dietary and stored body fat into substances called ketones. Your fat-burning system now relies mainly on fat – instead of sugar – for energy. While similar in some ways to familiar low-carb diets, the keto diet’s extreme carb restrictions – about 20 net carbs a day or less, depending on the version – and the deliberate shift into ketosis are what set this increasingly popular diet apart. In fact, other eating plans are pulling in keto elements, so you can find versions like eco-keto and at least one commercial diet that incorporates keto-friendly products.
Implementing the diet can present difficulties for caregivers and the patient due to the time commitment involved in measuring and planning meals. Since any unplanned eating can potentially break the nutritional balance required, some people find the discipline needed to maintain the diet challenging and unpleasant. Some people terminate the diet or switch to a less demanding diet, like the modified Atkins diet or the low-glycaemic index treatment diet, because they find the difficulties too great.[42]
When your body burns its stores of fat, it can be hard on your kidneys. And starting a ketogenic diet -- or going back to a normal diet afterward -- can be tricky if you’re obese because of other health issues you’re likely to have, like diabetes, a heart condition, or high blood pressure. If you have any of these conditions, make diet changes slowly and only with the guidance of your doctor.
Around this time, Bernarr Macfadden, an American exponent of physical culture, popularised the use of fasting to restore health. His disciple, the osteopathic physician Dr. Hugh William Conklin of Battle Creek, Michigan, began to treat his epilepsy patients by recommending fasting. Conklin conjectured that epileptic seizures were caused when a toxin, secreted from the Peyer's patches in the intestines, was discharged into the bloodstream. He recommended a fast lasting 18 to 25 days to allow this toxin to dissipate. Conklin probably treated hundreds of epilepsy patients with his "water diet" and boasted of a 90% cure rate in children, falling to 50% in adults. Later analysis of Conklin's case records showed 20% of his patients achieved freedom from seizures and 50% had some improvement.[10]
That’s not to say everyone starting out on a keto diet ends up wholly incapacitated for days. “You might find that you fatigue more quickly or that exercise seems harder than normal,” says Seattle-based nutritionist and Academy of Nutrition and Dietetics spokesperson Ginger Hultin, MS, RDN. Your body might also have an easier time transitioning (read: fewer symptoms) if you were already eating a relatively low-carb diet, Mancinelli explains.

Adopting a ketogenic diet may also hamper athletic performance, says Weiss, even though many athletes try it, thinking it will have the opposite effect. In a recent study in the Journal of Sports Medicine and Physical Fitness, Weiss and his colleagues found that after four days on a keto diet, participants performed worse on anaerobic exercise tasks—which involve short bursts of intense activity—than those who’d recently gone on a high-carb diet.
That said, you don’t have to jump in with both feet. Schmidt recommends trying to eat under 200 g of carbs a day initially (a moderate-carb diet) and then adjust lower based on how you feel. “If you start paying attention to the carbs in your diet, you’ll eat fewer processed foods,” she says. And it’s those whole foods that are the basis of good health.

In 1994, Hollywood producer Jim Abrahams, whose son's severe epilepsy was effectively controlled by the diet, created the Charlie Foundation for Ketogenic Therapies to further promote diet therapy. Publicity included an appearance on NBC's Dateline program and ...First Do No Harm (1997), a made-for-television film starring Meryl Streep. The foundation sponsored a research study, the results of which—announced in 1996—marked the beginning of renewed scientific interest in the diet.[1]
The ketogenic diet has been studied in at least 14 rodent animal models of seizures. It is protective in many of these models and has a different protection profile than any known anticonvulsant. Conversely, fenofibrate, not used clinically as an antiepileptic, exhibits experimental anticonvulsant properties in adult rats comparable to the ketogenic diet.[58] This, together with studies showing its efficacy in patients who have failed to achieve seizure control on half a dozen drugs, suggests a unique mechanism of action.[56]
A survey in 2005 of 88 paediatric neurologists in the US found that 36% regularly prescribed the diet after three or more drugs had failed, 24% occasionally prescribed the diet as a last resort, 24% had only prescribed the diet in a few rare cases, and 16% had never prescribed the diet. Several possible explanations exist for this gap between evidence and clinical practice.[34] One major factor may be the lack of adequately trained dietitians who are needed to administer a ketogenic diet programme.[31]
Certainly, prioritizing sleep, hydration, and overall healthy habits can keep you from feeling even worse, whether you’re on the keto diet or not. But the experts we spoke with agreed that avoiding ketosis altogether is a smarter way to feel good while you’re trying to lose weight, rather than putting a Band-Aid on something that could have more serious consequences down the road.
Implementing the diet can present difficulties for caregivers and the patient due to the time commitment involved in measuring and planning meals. Since any unplanned eating can potentially break the nutritional balance required, some people find the discipline needed to maintain the diet challenging and unpleasant. Some people terminate the diet or switch to a less demanding diet, like the modified Atkins diet or the low-glycaemic index treatment diet, because they find the difficulties too great.[42]
If you feel as if you’re starving, you’re likely to feel tired and want to give up your diet. But a ketogenic diet should not result in hunger, making it sustainable and possibly making you feel great. So eat enough protein foods and low-carb veggies, with enough added fat to feel satisfied. If you’re hungry all the time, check that you are getting adequate amounts of protein at most meals and, if so, add more fat to your meals (like more butter, more olive oil, or some delicious sauces). Our keto recipes have plenty of fat included, but you can adjust up or down, according to your own needs.
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