What You Need to Know About the Ketogenic Diet
Is the keto diet right for you? Learn all about it.
The ketogenic diet may seem like the latest weight-loss craze, but it’s actually been around for nearly a century. Developed in the 1920s, this ultra-low-carb, high-fat eating plan was originally used to treat seizures in people with epilepsy. Today, it’s getting some serious attention for an entirely different reason. “There’s growing research showing that the ketogenic diet is effective for managing blood sugar in people with diabetes,” says William Yancy, MD, program director at the Duke Diet and Fitness Center in Durham, North Carolina. “However, because we don’t have studies [lasting] longer than two or three years, we don’t know what can happen with regard to complications over longer periods of time.”
That hasn’t stopped its followers. Whether you’re considering it yourself or just curious what all the buzz is about, read on to find out what you need to know.
The Diet Defined
Despite its explosive popularity, there’s a lot of confusion about what the ketogenic (keto) diet really is. “Many people think they’re following a keto diet when they’re really just consuming a low-carbohydrate diet,” says Patti Urbanski, MEd, RD, CDE, a certified diabetes educator with St. Luke’s Hospital in Duluth, Minnesota. “So one person’s ‘keto diet’ may look very different than another’s.”
The backbone of a keto plan is its extraordinarily high fat content, making up 65 to 80 percent of calories daily. Protein—which can raise blood glucose, though not as much as carbohydrate does—makes up 15 to 25 percent of calories on the keto diet. And carbs are even more heavily restricted to just 5 to 15 percent of calories. That’s only about 20 to 50 grams a day (compared with the average 245 grams daily), or the amount in a small apple or a cup of cooked brown rice, respectively.
How does it work? Normally the body runs on glucose for fuel. However, with less glucose on board, the body converts fat to substances called ketones that it uses for energy, resulting in a state known as ketosis. In addition to increased fat burning, ketosis is also believed to accelerate weight loss by suppressing appetite.
Sound familiar? Long before insulin became available in the 1920s, a very low carbohydrate diet—often with as many as 75 percent of calories from fat—was the mainstay of blood glucose management for people with diabetes. This made Yancy and his team wonder if this age-old diet might have some benefits for people with diabetes today.
The Science Says
While many health care providers aren’t comfortable recommending the keto diet for people with diabetes, there’s a substantial body of research indicating that it can help with weight loss, reduce the need for medication, and even lower A1C into the non-diabetes range. It’s so effective that when researchers assigned 349 volunteers with type 2 diabetes to follow either a keto diet or a traditional diabetes eating plan (the makeup of that plan wasn’t defined in the study) for one year, they observed some powerful results. While the people on the “diabetes diet” didn’t experience any positive movement in their A1C, body weight, or medication requirements, those on the keto plan reduced their A1C from 7.6 to 6.3 percent, shed 12 percent of their body weight, eliminated their need for sulfonylurea medication, and lowered or reduced their need for insulin by 94 percent. The results were published in 2018 in the journal Diabetes Therapy.
Yancy has seen similar results in his practice. “Carbohydrate intake is the main driver of blood sugar. So if you’re able to lower blood sugar by reducing carbohydrate intake, then you may be able to reduce diabetes medication,” he says. “We’ve seen people come off of hundreds of units of insulin just by changing the way they eat, and that can happen really quickly, in just a few weeks.”
There’s plenty of research suggesting benefits of a keto diet for people with type 2 diabetes, but studies for type 1 are more limited and less conclusive. For example, a small study of 11 adults with type 1 diabetes published last year in Diabetic Medicine found the keto diet to be extremely effective for lowering A1C.
A Balancing Act
The keto diet’s ability to reduce A1C may also be one of its greatest dangers. In the Diabetic Medicine study, those A1C reductions came at the price of frequent low blood glucose (hypoglycemia), calling into question the diet’s short-term safety.
“If someone with diabetes is [taking insulin or oral type 2 meds in the sulfonylurea or meglitinide class and is] following this diet, they need to know that their blood sugar can drop really quickly, so it’s critical that they check it more frequently,” says Toby Smithson, MS, RDN, CDE, author of Diabetes Meal Planning & Nutrition for Dummies. “Don’t wait for it to happen. Meet with your doctor or diabetes educator in advance so that you can troubleshoot exactly what to do if your blood sugar drops.” If it’s an infrequent occurrence, you may be advised to treat with fast-acting glucose. But frequent lows may require medication adjustments or the addition of more carbs to your eating plan.
To minimize the risk of hypoglycemia, Yancy and his team decrease medication as soon as a patient starts the diet. While drugs like metformin and liraglutide (Victoza) are less of a concern, there are others that pose a substantial hypoglycemia threat. In addition to insulin, the sulfonylurea drugs glipizide and glyburide require a watchful eye, as they work by stimulating the pancreas to make more insulin, increasing the risk of dangerous lows in the face of insufficient carbohydrate intake. “People on this diet need to be prepared to check their blood glucose any time they feel like it could be getting too low,” says Urbanski. “I would say a minimum of twice a day, but ideally three to four times a day, at least in the beginning in order to see the effect of the diet on their blood glucose readings.”
Eyes Wide Open
To stay healthy on the keto diet, know its drawbacks from the start—and work with your health care provider to plan ways around them.
- Missing Nutrients. One of the biggest concerns for dietitians is the keto diet’s lack of key foods. Many question the eating plan’s impact on the development of certain chronic diseases. Without milk, for example, getting enough calcium and vitamin D for sturdy bones becomes a challenge. Take away whole grains, fruit, beans, and potatoes, and it’s nearly impossible to consume enough potassium for healthy blood pressure or enough fiber to stay regular. And unless you’re eating lots of low-carb, leafy green vegetables, you miss out on vitamins A, C, K, and folate, too.
- Cost. At the grocery store, your shopping cart can take on a whole new look (and price tag) thanks to high-ticket items such as beef, fish, poultry, pork, and cheese, which are replacing budget-friendly pasta, potatoes, rice, and bread. And chronic constipation may require fiber supplements or stool softeners. Before beginning a keto diet, determine whether it’ll fit within your budget.
- Kidney Danger. Some health professionals worry about the impact of so much protein on kidney health. Most experts agree that the keto diet isn’t a good fit for anyone with chronic kidney disease; both Urbanski and Yancy, however, believe there’s little concern for people with healthy kidneys.
- Dehydration. With fewer water-binding carbohydrates in the diet, the body is less able to hold onto fluids, which can lead to dehydration. Eating more salt can help offset this, but it can also raise blood pressure, creating a whole new set of issues. If you plan to follow a keto diet, hydration is key. To know how many ounces of fluid you need each day, Yancy recommends dividing your body weight in half. Then think of the resulting number as your daily fluid goal in ounces. So if you weigh 200 pounds, strive for 100 ounces of water a day.
- Difficulty. Many experts question how long a person can realistically give up carbs. “This is a very restrictive diet that requires a drastic change in eating behaviors and even taste,” says Sandra Arevalo, MPH, RDN, CDE, a certified diabetes educator and spokesperson for the Academy of Nutrition and Dietetics. “It isn’t very practical or easy to maintain, for people both with and without diabetes.” That’s not saying you can’t stick with it, but before you commit, make a plan and set measurable goals to help you stay on track. Being prepared with the right foods can also help. Urbanski recommends making a shopping list that focuses on a few basic keto-friendly meals and snacks, so you’ll always have the right foods on hand to ensure success.
The Long Term
One of the most-cited worries about the keto diet is the long-term impact it may have on heart health—especially because people with diabetes are at greater risk for heart disease. In the small Diabetic Medicine study that found people with type 1 improved their A1Cs on a keto diet, participants had higher triglycerides and LDL (“bad”) cholesterol. This raises concerns about the diet’s longer-term heart health implications, as do the results of research published last year in The Lancet. That study followed more than 15,000 adults for 25 years and found that people who consumed less than 40 percent of their calories from carbohydrates were significantly more likely to die from heart disease than those whose diets contained 50 to 55 percent of calories from carbs—especially if the foods that replaced those carbs were rich in animal fats and proteins.
“Because most of the calories on this plan come from fat, there’s a real concern about heart health,” says Urbanski. “There’s currently a lot of debate regarding saturated fat and its impact on cardiovascular disease risk.”
Yancy also has concerns. “At this point, no long-term studies have been performed to examine whether a low-carbohydrate eating pattern lowers one’s risk for cardiovascular events or mortality,” he says. “In fact, there is a dearth of high-quality, randomized-trial evidence to support any particular eating pattern.”
To lower your heart risks while following a keto diet, be mindful of the types of fats you’re eating. “Most nutritionists encourage people to get their fat from heart-healthy mono- and polyunsaturated fats,” Urbanski says. So even though going keto may sound like a license to load up on bacon and butter, reach for unsaturated fats from foods such as olives, nuts, seeds, and avocados, and olive, canola, and nut oils.
The Bottom Line
“Health professionals have been hesitant to encourage this eating plan, but there may be a potential role for it in diabetes management,” says Urbanski. “Over the last five years, my outlook on very low carbohydrate diets, including the keto diet, for people with type 1 and 2 diabetes, has really changed.”
Ketosis vs. Ketoacidosis
If you’re wondering about the difference between ketosis and diabetic ketoacidosis, you’re not alone. “The word ketone is scary for most people with type 1 diabetes because they relate ketones to diabetic ketoacidosis,” says Patti Urbanski, MEd, RD, CDE, a certified diabetes educator with St. Luke’s Hospital in Duluth, Minnesota. “But with the ketogenic diet, we’re talking about a much lower level of ketones.”
Why does this matter? Ketosis is a completely normal physiological process that occurs when our bodies run low on carbohydrates, turning to fat for fuel instead. It happens when you skip breakfast, go too long between meals, or exercise extra hard. And it happens when you follow a very low-carb eating plan like the keto diet.
Ketoacidosis, on the other hand, is dangerous. But it’s usually limited to people with type 1 diabetes, striking when their glucose levels rise due to illness or a missed insulin dose. Without insulin, cells can’t take in glucose, so they burn fat for fuel instead, producing exceptionally high ketone levels—much higher than the amount generated by the keto diet. That, in combination with high blood glucose levels, essentially poisons the blood. “It’s very easy to tell the difference between nutritional ketosis, which has no negative symptoms [aside from ‘keto breath,’ which can smell like nail polish remover], and dietary ketoacidosis, which is an illness that requires hospitalization and causes lethargy, abdominal pain, nausea, vomiting, rapid breathing, and lack of appetite,” says William Yancy, MD, program director at the Duke Diet and Fitness Center in Durham, North Carolina.
Keto Flu: Fact or Fiction?
For many people, one of the more surprising side effects of starting a ketogenic diet is a bout with the “keto flu.” How so? “When you go on this diet, your kidneys don’t retain as much salt or water, which can lead to flu-like symptoms, such as fatigue and headache, or constipation,” says Laura Saslow, PhD, an assistant professor at the University of Michigan School of Nursing. “But these are typically short-lived symptoms that can be prevented or treated by increasing your salt and water intake.” However, if you have high blood pressure, speak with your doctor before adding more sodium to your diet. And know that the keto flu only lasts a week or two; symptoms typically subside once the body adjusts to the diet.
What Can I Eat?
- full-fat Greek yogurt (small portions)
- chicken and turkey
- fish and shellfish
- pork and beef (small portions)
- nuts and nut butters
- sunflower and pumpkin seeds
- low-carb vegetables such as: spinach, kale, and lettuce; broccoli and cauliflower
- unsweetened fortified almond milk
- olive, canola, avocado, and nut oils
- milk, bread, pasta, cereal, beans, fruit (other than berries), root vegetables (such as carrots and potatoes), corn, alcohol
Keto in a Day
Wondering what the ketogenic diet looks like in real life? This sample meal plan provides a one-day snapshot.
Breakfast: Almond buter yogurt sunday (swirl 3 tablespoons almond butter into 2/3 cup full-fat plain Greek yogurt and top with 3/4 cup raspberies)
Snack: 1 1/2 ounces brie cheese
Lunch: Chicken-kale salad (toss 3 cups baby kale with 2/3 sliced avocado, 2 ounces grilled chicken, 1 tablespoon olive oil, and 2 teaspoons red wine vinegar
Snack: 15 kalamata olives
Dinner: 4 ounces broiled salmon and 1 cup cooked broccoli drizzled with 1 tablespoon avocado oil
Total Nutrition: Calories 1,620, Total Fat 127 g (Sat. Fat 25 g), Cholesterol 195 mg, Sodium 1,520 mg, Potassium 2,765 mg, Total Carbohydrate 49 g (Fiber 25 g, Sugars 16 g), Protein 85 g, Phosporus 1,130 mg
Choices: Fruit 1, Whole Milk 1, Nonstarchy Vegetable 4, Carbohydrate 0.4, Lean Protein 8, Fat 20