But researchers have taken a greater interest in it as a medical diet, too. In 2015, there were 159 studies listed in the database PubMed (which is run by the U.S. National Library of Medicine and the National Institutes of Health). In 2018, that number doubled, with 322 published studies. After you follow the diet for a few days, your body enters ketosis, which means it has started to use fat for energy. Newbies on the diet find it helpful to track whether they’re in ketosis with a urine ketone strip or a blood-prick meter, but Nisevich Bede says you’ll eventually learn what ketosis feels like and will know whether you’re in it.
Keto-Friendly Foods
Here are some of the foods you may eat on keto:
Oils (like olive oil, avocado oil, and coconut oil)AvocadoHeavy creamButterCream cheeseCheeseCoconut (unsweetened)Nuts (almonds, macadamia) and seeds (chia seeds, flaxseed, sunflower seeds)Leafy green vegetables (romaine, spinach, kale, collards)Nonstarchy vegetables, including zucchini, asparagus, cucumber, broccoli, cauliflower, and bell peppersMeats (chicken, beef, pork, lamb)EggsFish (particularly fatty fish like salmon and sardines)
What You Can’t Eat (or Drink) on the Keto Diet
Foods and drinks that you’ll avoid on the keto diet include many whole fruits (though some fruits are keto-friendly), dried fruits, whole grains, cold cuts, chicken nuggets, milk, ice cream, alcohol, and desserts. Snack Full-fat cottage cheese topped with pine nuts Lunch Spinach salad with a grass-fed burger on top, cheese and avocado Snack Roasted, salted almonds Dinner Grilled salmon with a side of broccoli topped with butter The only clear and proven health benefit of the keto diet is reducing epileptic seizures in children. In fact, doctors have been using keto therapeutically for this purpose since the 1920s. Keto is often suggested for children who suffer from certain disorders (like Lennox-Gastaut syndrome or Rett syndrome) and don’t respond to seizure medication, according to the Epilepsy Foundation. (1) They note that keto can decrease the number of seizures these children have by half, with 10 to 15 percent becoming seizure-free. In other cases, it may also help patients reduce the dose of their medication. The keto diet may also be beneficial for adults with epilepsy, though the Epilepsy Foundation notes that it’s less frequently recommended for this group because it is so restrictive and difficult to stick with. (1) One study, published in May 2016 in the journal Epilepsy & Behavior, found the diet reduced the frequency of seizures for many study participants, 7 percent of whom were seizure-free at the four-year mark. (2) And though it wasn’t the goal for this study, nearly 20 percent of the participants lost weight while following the diet. Initially, the weight loss comes from loss of water because you cut down on carbs in your diet and your body uses up the carbohydrates stored in the liver, which hold onto water. The diet results in further weight loss because it encourages you to load up on whole, high-fat foods, Nisevich Bede says. By cutting carbs, you’ll also cut sugar and simple, refined carbohydrates, which means a steadier supply of energy. (No more sugar highs and crashes!) Once their bodies are used to the diet, “The first thing people report is, ‘Oh my gosh, I have this steady energy and I don’t have the need to snack at 3 p.m. because my energy is waning,’” Nisevich Bede says. Research published in January 2015 in the journal Obesity Review showed that the keto diet may lead to fewer hunger pangs and a lower desire to eat. (3) You lose weight temporarily because “if you’re not hungry every five minutes and can work on your willpower,” you won’t eat as much, Nisevich Bede says. But while some research is promising — one study published in October 2013 in the British Journal of Nutrition found that the keto diet led to greater weight loss than a low-fat diet, for example (4) — there is a lack of long-term research (greater than two years) that suggests a highly restrictive diet like keto is superior for weight loss than others, and it’s certainly not right for everyone. In the 2019 U.S. News & World Report Best Diets rankings, keto lands at number 38 of 41 diets profiled. (5) That’s because while it may lead to a short-term weight loss, experts flag how difficult it is to follow, the lack of nutrition, and potential health risks from cutting major food groups and eating more saturated fat.
Metabolic Syndrome Limited research, including a study published in November 2017 in the journal Diabetes & Metabolic Syndrome: Clinical Research & Reviews, has suggested that adults with metabolic disease following keto shed more weight and body fat compared with those on a standard American diet, which is heavy in processed food and added sugars. (6)Type 2 Diabetes Research published in September 2016 in the Journal of Obesity & Eating Disorders suggested the diet could help people with type 2 diabetes and can lead to improvements in HbA1c levels (though be warned, it can also lead to hypoglycemia — that’s low blood sugar levels — if you take medication to lower your blood sugar). (7)
Other potential risks include kidney stones, several vitamin and mineral deficiencies, decreased bone mineral density, and gastrointestinal distress. (7) Here’s why: When you’re eliminating certain food groups (like fruits, legumes, and whole grains) and severely limiting others (like many vegetables), it’s not uncommon to experience nutritional deficiencies. A lack of fiber, for instance, can make it more likely you’ll experience constipation. In order to avoid some of these risks, the diet needs to be well planned to ensure you’re hitting all of your nutritional bases. Unfortunately, a restrictive diet makes this planning a challenge, especially if you’re not working with a registered dietitian who is knowledgeable in keto. And while some fats can be healthy, there’s a risk that in following a high-fat diet, you’ll increase your intake of unhealthy trans and saturated fats. These “bad” fats are found in things like red meat, poultry skin, cheese, and butter, and can lead to an increase in LDL, or “bad” cholesterol and increased risk of heart disease. (14) This is a controversial issue, as some experts do recommend adopting a low-carbohydrate diet to lower heart disease risk. If you’re at risk or have heart disease, it’s important to speak with your doctor first about your health needs. Bottom line, the hype around this diet is tempered by the fact that researchers just don’t know about the long-term safety of following a high-fat diet (particularly one that may be high in saturated fat). People With Type 1 Diabetes These individuals are insulin-dependent, and a keto diet could lower their blood sugar to dangerous levels, says Moree. People With a History of Eating Disorders Going on a strict diet that eliminates food groups could trigger a relapse if you have a personal history of having an eating disorder. And while there’s a growing popularity in treating binge eating disorder (BED) with keto, experts strongly advise against it. Treatment of BED requires regular, adequate food intake without restriction, says Sumner Brooks, MPH, RDN, a certified eating disorder dietitian in Portland, Oregon. People Who Have Had Their Gallbladder Removed A gallbladder holds bile, which aids in fat digestion. Without this organ, you will not feel your best on a high-fat diet. People With Thyroid Disease A a keto diet may suppress levels of thyroid hormones, says Audrey Fleck, RDN, an integrative and functional nutritionist and certified diabetes educator in Perkasie, Pennsylvania. That means the diet has been touted as a treatment for hyperthyroidism; nonetheless, the approach is controversial. People With Multiple Sclerosis (MS) The National Multiple Sclerosis Society raises questions about the long-term safety of the diet for MS, and cautions about the possible side effects, like fatigue and constipation. (15) If you’re looking to lose weight, keep in mind that the diet likely requires a complete overhaul to the way you normally eat. But it may be worth it if you’re looking to lose weight or have one of the health conditions it’s been shown to help with. To be on the safe side, be sure to discuss with your doctor whether the keto diet is right for you before you drastically change your eating habits. While the diet has roots in medicine, its widespread use is still new, and not every doctor understands the keto diet. For more information, you can look to national programs that are gaining steam. Two examples: Virta Health, where they are studying the diet’s role in prediabetes and type 2 diabetes treatment, and the Cleveland Clinic’s Functional Ketogenics Program. Additional reporting by Moira Lawler.
