The Keto Diet: Healthful or Harmful for Diabetes?

As a registered dietitian nutritionist and certified diabetes educator specializing in diabetes, I find that many of the patients I see in Overlake’s Diabetes Education and Outpatient Nutrition clinics are following or have followed the ketogenic, or “keto,” diet in an effort to lose weight or manage their diabetes.

The diet is pervasive and heavily marketed. There are keto products everywhere! Does the diet work? Is it safe? Is it effective?

How does the keto diet work?

When a diet that contains carbohydrate is consumed, the carbohydrate is broken down into glucose, and that glucose is absorbed through the small intestine. Cells then use that glucose for energy, and glucose not used immediately is stored in the liver and muscle as glycogen. When carbohydrate is strictly limited, the body turns to fat and protein for fuel or energy. It takes about three to four days for your body to run out of glucose for energy. When this happens, and you convert to using proteins and fats for fuel, this is called ketosis.

What is the keto diet?

As you may know, or have guessed, the keto diet is a low-carb diet, which means you can generally have about 50 grams per day, depending on who’s defining it. The keto diet is also high in fat, about 70 to 80 percent of total daily calories. In general, most carbs are off limits including whole grains; starchy vegetables such as potatoes, corn and winter squashes; many types of fruit and all fruit juices; dairy products; legumes such as lentils, peas, beans and peanuts; and condiments high in sugar content including barbecue and teriyaki sauces and white and brown sugar, honey, maple syrup and agave.

The diet permits berries, low-carb vegetables, eggs, meats, poultry, seafood, cheeses, nuts and seeds, avocado, avocado and coconut oils, unsweetened tea and coffee, butter and cream. 

What are the benefits for diabetes? What are the downsides?

There are only short-term studies on the diet, many of which have included very few participants, but the outcomes have been positive. The positive outcomes include a reduction in A1c (blood sugar levels) and weight loss. However, the downsides to the diet include increased risk of kidney stones and gout, constipation, and nutritional deficiencies in vitamins and minerals such as calcium, Vitamin D, magnesium, zinc and iron. There also could be a negative impact on gut health from decreased intake of fruit and whole grains.

Those with kidney disease or a history of kidney transplant, gestational diabetes, or are pregnant with diabetes should not follow this diet. Some experts don’t recommend this diet for those with type 1 diabetes.

As a nutrition and diabetes specialist, I do not recommend the keto diet because it restricts the foods that are protective against chronic diseases like diabetes. I am not an advocate of diets as they are not sustainable, do not work long-term and potentially can cause emotional harm and adverse health outcomes.

Always consult your healthcare provider before making any major changes to your diet or lifestyle, especially if you have a chronic disease.