Kourtney Kardashian recently blogged about trying a diet that dates back to the 1920s, when it was first used to treat pediatric epilepsy: the ketosis (aka keto or ketogenic) diet.
Kourtney said she jumped on board to alleviate high levels of mercury and lead within her body — more on that below — but many people use the diet for weight loss or other health issues. Interest in the eating approach began to pick up in 2016 and soared in January 2018, according to Google Trends. “People are recognizing the value of eating whole foods,” says registered dietitian Amy Goss, PhD, assistant professor of nutrition sciences at University of Alabama At Birmingham’s Nutrition Obesity Research Center, of the diet’s newfound popularity.
Here’s what you need to know about the diet everyone’s been talking about:
WTF Is Ketosis?
Ketosis is a metabolic state in which fat becomes the body’s primary fuel source instead of usual its go-to: blood sugar (aka glucose) which is derived from carbs you eat. Typically, eating carbs triggers the release of the hormone insulin, which helps cells use glucose for energy.
When you follow a high-fat, moderate protein, low-carb diet, glucose levels remain steady, and insulin doesn’t surge. Instead, dietary or body fat is broken down into organic compounds known as ketones. “Ketones are a good source of fuel,” Goss says. “Your brain loves them, your muscles can metabolize them, and your body can’t really store them as fat.”
An at-home urine test can confirm whether it’s working, since ketosis is marked by the presence of ketones in the blood and urine. “The strip changes color when you’re burning fat as fuel,” Goss says. “It’s a surefire way to tell whether your body is metabolizing fat, which provides positive reinforcement without stepping on a scale.”
What to Eat on a Ketogenic Diet
The easiest way trigger ketosis is to consume no more than 20 to 50 grams of carbs a day from whole foods like vegetables that barely affect your blood sugar. “I think of it as a whole-foods diet that cuts out processed stuff and grains,” Goss says, comparing the dietary components to Whole 30, although it doesn’t necessarily lead to ketosis.
About 90 percent of calories should come from fat, with the remaining 10 percent split between carbs and protein, says Dr. Mackenzie Cervenka, M.D., associate professor of neurology and medical director of the Johns Hopkins Hospital Adult Epilepsy Diet Center, and ketosis researcher.
While veggies and some cheese contain trace amounts of carbs, most are permissible, as are oil, eggs, seafood, poultry, and meats, which contain virtually no carbs, according to the United States Department of Agriculture’s Agricultural Research Service.
However, a medium-size apple contains 25 grams of carbs, while a bagel has 48 grams, and a cup of brown rice has 52 grams; these foods, and other sources of starch and sugar — including most fruits — are prohibited on the keto diet since they raise your blood sugar.
Nonetheless, since cutting back on carbs can lead to vitamin and mineral deficiencies, it’s smart to consult a doctor about adding supplements to your diet before jumping in, Dr. Cervenka says.
Technically, the diet permits most liquors and dry wines (most reds, some rosé, and whites like Chardonnay and Pinot Grigio), which are low in sugar and carbs. Although alcohol is digested differently from carbs, so it doesn’t interfere with ketosis, booze doesn’t exactly help if weight loss is the goal since alcohol is caloric, and is processed in the liver, which can’t simultaneously oxidize fat, Goss says.
There are many different ways to trigger ketosis, including Kim Kardashian’s go-to approach: The Atkins Diet, a multi-phase, low-carb eating plan. “Atkins can be ketogenic, especially in the early phases,” says registered dietitian Jeff Volek, PhD, a professor at The Ohio State University and author of The Art and Science of Low Carbohydrate Living, “but it often includes enough carbs or protein in latter phases that is not associated with elevated ketones.”
Certain supplements also may help the body create ketones. An example is medium chain triglycerides oil (like the stuff found in Bulletproof Coffee some fitluencers swear by for breakfast) which is absorbed differently from other fats: It goes straight to the liver, where it forces the body to produce ketones, Goss says. “If you add it without changing the rest of your diet, and your insulin levels are still high, I don’t know if you’d benefit,” she adds.
What The Keto Diet Is Used For
Weight loss: Typical dieters who cut back on calories to lose weight shed body fat and muscle mass indiscriminately, but the keto diet selectively reduces body fat while preserving muscle mass, according to Goss. For this, researchers credit ketogenesis’ fat-burning effects. Meanwhile, the diet itself, which includes foods rich in fat, protein, and fiber, and levels blood-sugar spikes that make you hungry, keeps dieters feeling satisfied. “It naturally helps people self-regulate their food intake without restricting food portions,” Goss says.
Meanwhile, Goss says her patients often report higher energy levels. “Ketone energy can’t be stored, so people are compelled to use it and may end up more active,” she says.
Beware, though, that initial weight loss often results from the loss of fluids, not fat, she says. That’s because, on a low-carb diet, the body produces less insulin, and insulin make the body retain water. Meaning: As soon as a keto dieter falters, and insulin levels soar, lost pounds easily can return.
Those who stick with the diet report mental clarity and improvements in concentration, according to Dr. Cervenka. (Remember: Ketones are A+ brain fuel.)
Detoxification: While Goss says there’s no research-backed reason why Kourtney’s doctor prescribed a keto diet to eliminate excess mercury and lead in her system, she has an untested theory: Research suggests certain toxins can sometimes be stored in body fat, which is mobilized by the keto diet. And yet? “I can’t say there’s a scientific basis for that recommendation,” Goss says. (After all, most detoxes are bullsh*t.)
Seizures: The ketogenic diet was first used to treat pediatric epilepsy without medication, since ketosis helps neurons function properly, both by suppressing the hyper excitability and inhibition that leads to seizures, according to Dr. Cervenka.
Diabetes: Type 1 diabetics need insulin shots to clear sugar from their blood streams, but ketosis does the same thing through dietary tweaks. Type 2 diabetics, on the other hand, are basically carb intolerant, according to Goss. Since the keto diet calls for very few carbs, research shows it can be a cure-all that helps patients wean off medication with a doctor’s supervision, she says.
Cancer: In addition to chemotherapy or radiation, dietary changes that promote ketosis are also being studied for improving cancer outcomes, according to Goss. That’s because, unlike healthy cells, which can use ketones for fuel, certain cancer cells require glucose to replicate and need insulin to absorb it, she says, citing promising research. Because ketosis lowers insulin levels, it can starve cancer cells, effectively stalling their growth.
Alzheimer’s: “Alzheimer’s may originate from insulin resistance in the brain,” Goss says, citing emerging research that supports the theory. “Compared to glucose, ketones are excellent fuel for the brain, and might aid in prevention or treatment.”
Polycystic ovary syndrome: Research suggests the low-carb diet, which helps balance hormone levels, may alleviate symptoms of this endocrine disorder, such as irregular periods and excess hair growth. Benefits may be tied to weight loss resulting from ketogensis.
Heart health: People think high-fat intake is detrimental to heart-disease risk, but that’s not necessarily the case on the keto diet,” Goss says. “Cholesterol levels improve with fewer markers of inflammation.”
Endurance: Ultra-marathoners who burn through carb-rich meals in a snap often train in ketosis to help their bodies move more readily between carb- and fat-burning modesduring competitions, Goss says: “They manipulate the way their muscles use fuel so they can get more without replenishing.”
The Downsides of the Keto Diet
No diet is perfect — and this one isn’t all avocado, salmon, and sunshine, either. Short-term side effects are common, according to Goss, who says they can include:
“Keto flu”: Depending on a person’s baseline diet and its carbohydrate content, the drop in insulin that results from changing things up can trigger flu-like symptoms such as fatigue, nausea, and headaches for the first few days, Goss says, citing dehydration from initial fluid loss as a likely cause. Symptoms typically go away on their own, but drinking water, a high-sodium broth, or a sugar-free electrolyte drink can help.
Bad breath: Ketosis can produce an organic compound called acetone that’s eliminated by the lungs, which can make your breath smell sweet, or metallic or like poop, depending on who’s sniffing.
Digestive issues: Constipation and bloating are common complaints among keto dieters: “TMI, it felt like I had a softball in my butt all the time,” one Redditor wrote after six months on the diet. Since you retain less water on the keto diet, dehydration could be to blame, as well as lack of fiber. However, eating high-fiber foods like veggies and drinking plenty of water can help, Dr. Cervenka says.
Kidney stress: One rare but potential side effect of forgoing carbs: High concentration ketones can make your blood acidic, according to Dr. Cervenka, who says this can lead to kidney stones. (The average keto dieter need not worry, she says.)
The Bottom Line
Cutting out foods like pizza, fries, cupcakes, and bread are only the half of it: The keto diet eliminates nutritious options like fruit, yogurt, whole grains like rice and quinoa, and hummus — HUMMUS! — just because they interfere with ketosis. “It’s a perfectly healthy way to eat,” Goss says of the keto diet. “But I wouldn’t recommend it for people without an underlying metabolic condition. For the average person, it’s not necessary to be that restrictive. A diet that emphases whole foods is the best, healthiest approach.”