More and more, I am finding an increasing number of people are limiting their carbohydrate intake and doing some form of a ketogenic diet. There is significant misunderstanding about this kind of eating pattern and its long-term health consequences.

Carbohydrates are the body’s primary energy source. The preferred fuel for the brain is glucose, the result of carbohydrate digestion. With the help of insulin, it enters your body’s cells and fuels all your activities — whether one is going for a jog or simply breathing. Extra glucose is stored in your liver, muscles, and other cells for later use, or is converted to fat. When our brain does not have access to glucose, it will “dampen” brain electrical activity.

During starvation or fasting states where adequate carbohydrate is not available, the body has an emergency back-up plan whereby it can use ketones as an energy source. Normally produced by the liver in low amounts, ketone production increases (ketosis) when there are inadequate amounts of glucose in the body. First the body uses carbohydrate stores for glycogen conversion to glucose. Then the body turns to protein stores from muscle to make glucose, or gluconeogenesis; lastly it can use fat stores which results in ketosis.  However, ketones can only be used by some of our cells, meeting only 50% of basal metabolic needs and 70% of the brain’s energy needs. 

Getting the body to a state of ketosis is not as simple as it seems. It generally takes up to several weeks during which people often experience nausea, fatigue, headaches, and muscle aches, which some call the “keto flu”. In the initial period lean muscle mass is lost and then only if one adheres strictly to the diet, will there be fat loss. Eat fruit, more vegetables, bread, pasta, cereal, lentils, beans, seeds, or nuts and the body will quickly move out of ketosis and back to using its preferred fuel, carbohydrates.

Ketogenic diets generally include 75-90% of calories from fat, less than 10% from carbohydrates and the remaining 5-15% of calories from protein sources. This means a diet high in saturated fat including various meats, eggs, and plenty of oils. Initially a century ago, this kind of diet was used to treat children with refractory epilepsy to prevent seizures. Although these children were on multiple anti-seizure medications, they continued to have seizures. As a last resort they were put on a high fat ketogenic diet. After some time to reach ketosis, their seizures diminished as they experienced diminished brain electrical activity. It makes me wonder why a healthy adult, without a similar condition would want to lessen their brain activity.

There are three macronutrients, carbohydrates, protein & fat. When we consume a diet reducing carbohydrates, there must be increases in the other two, protein and fat. Protein also triggers an insulin release, and excess calories from protein turn into fat, just like those of the other macronutrients. We can get all the protein we need from a diverse diet of plants. All plant foods provide all essential amino acids, in varying combinations.

Some people are attracted to this kind of diet for quick weight loss. This may initially occur due to less water retention in the body, as carbohydrates hold water. Others may be interested in improvements in blood sugar which may initially be seen due to restriction of calories & to eliminating processed foods (ie. refined carbohydrates including flours, and sugars) from the diet.  However, any method of weight loss & calorie restriction (including starvation, cancer, & drug addiction) will transiently improve glycemic control. It does not mean that these methods should be universally recommended or that they are health promoting.  

In fact, the short-term side effects of ketogenic diets include nutrient deficiencies, constipation, impaired glucose tolerance, elevated LDL cholesterol, impaired athletic performance, negative effects on bone and bad breath. In the long term, there are increased risks of colon cancer, heart disease, kidney stones, and even birth defects. Those on diets low in carbohydrates have increased risk for death from any reason, or all-cause mortality.

High intake of meat and low intake of fruits and vegetables are among the factors linked to premature death around the world. Routine intake of whole grains is clearly linked to reduced cardiovascular risk with better overall health and weight. Reliance on beans and other legumes as a primary source of protein is associated with reduced risk of all chronic diseases and premature death, enhanced vitality, and longevity. The keto diet generally emphasizes the foods most linked to global chronic disease and premature death and excludes nearly all the foods that promote lasting health.