What Is the Ketogenic Diet?

Keto is all the rage. The internet is filled with stories of how everyone from movie stars to ordinary people have shed stubborn pounds with the ketogenic diet. Some suggest this eating pattern also may be helpful for managing diabetes and warding off Alzheimer’s disease. So, is it a miracle diet or just the latest fad?

How the keto diet works

The ketogenic diet is a high-fat, moderate-protein, low-carbohydrate eating pattern, which differs from general, healthful eating recommendations. Many nutrient-rich foods are sources of carbohydrates, including fruits, vegetables, whole grains, milk and yogurt. On a keto diet, carbs from all sources are severely restricted. With the goal of keeping carbs below 50 grams per day, keto dieters often consume no breads, grains or cereals. And, even fruits and vegetables are limited because they, too, contain carbs. For most people, the keto diet requires making big shifts in how they usually eat.

Why does the keto diet restrict carbs?

Carbs are the main source of energy for our body. Without enough carbs for energy, the body breaks down fat into ketones. The ketones then become the primary source of fuel for the body. Ketones provide energy for the heart, kidneys and other muscles. The body also uses ketones as an alternative energy source for the brain. Hence, the name for this eating pattern.

For our bodies, a ketogenic diet is actually a partial fast. During a total fast or starvation state, the body isn’t taking in a food source of energy. When this happens, it breaks down lean muscle mass for fuel. With the keto diet, the ketones provide an alternative source of energy. Unlike a full fast, the keto diet helps to maintain lean muscle mass.

Is the keto diet safe?

This eating pattern is not recommended for individuals with:

• Pancreatic disease
• Liver conditions
• Eating disorders or a history of eating disorders
• Gallbladder disease or those who have had their gallbladders removed

Plus, there are both short-term and long-term health risks associated with the keto diet for all people. Short-term health risks include flu-like symptoms, for example, upset stomach, headache, exhaustion and dizzy spells. This is often called the “keto flu.” Some people also report trouble sleeping. Decreasing intake of high-fiber vegetables, fruits and whole grains may increase the risk of constipation. Often keto dieters must take a fiber supplement to help stay regular, but this should be discussed with a health care provider first.

Long-term health risks of the keto diet include kidney stones, liver disease and deficiencies of vitamins and minerals. Because so many nutrient-rich foods are cut out, vitamins A, C, K and folate levels usually are low.

The high-fat nature of the keto diet is very controversial. A considerable body of research has shown that diets high in saturated fat may increase the risk for heart disease and other chronic health problems. The risk that keto dieters might be taking with regard to their long-term cardiovascular health has not been fully studied.

What the science says about keto

The keto diet has been used to help manage epilepsy, a disorder characterized by seizures, for more than 100 years. More recent studies are evaluating the keto diet as an alternative dietary treatment for obesity and diabetes. Research on the benefits of the keto diet for these health conditions are limited. Most studies on the effectiveness of the keto diet in these groups has been done in small groups of people. Or, for some conditions like Alzheimer’s disease, the research has focused primarily on lab animals. To fully assess the safety of this eating pattern, more research is needed. Plus, studies must be done on the long-term health effects of the keto diet.

Body mass index and individual metabolic rates impact how quickly different individuals produce ketones. This means that on the keto diet, some people lose weight more slowly than others — even if they are following the exact same keto diet plan. For this group of people, the keto diet can be frustrating and may impact their motivation for making changes. Plus, many people are not able to stick with the keto diet and gain back the weight after returning to their previous pattern of eating.

The bottom line

The ketogenic diet is quite restrictive. Research supports this eating pattern for epilepsy when managed along with a health care team, since its treatment can be very complex. However, with regard to the keto diet as a tool for weight management and other health conditions, the jury is still out.

For a personalized weight management plan that meets your individual needs, consult a registered dietitian nutritionist. An RDN can create a personalized weight-loss program based on your unique health and nutrition needs and goals. To find a dietitian in your area, search the Academy's Find a Nutrition Expert database.