What is the Ketogenic Diet?
Sally Feltner, PhD, RDN
Glucose is the preferred fuel for the body to use for energy. However, when carbohydrates are limited there may not be adequate glucose for energy use. The body can make some glucose from protein but it can also supply an energy source from fatty acids called ketones.
Ketones ( ketosis) are molecules formed in the liver from fatty acids and released in the blood when there is not sufficient carbohydrate. Ketosis can be generated in a ketogenic diet by fasting or by strictly restricting carbohydrate intake to less than 20-40 grams a day. Fat intake is increased to about 70-80 percent of total calories. Protein intake makes up the rest of the calories.
Ketone production is a normal response to starvation or to a diet very low in carbohydrate. Ketones can be used for energy by the heart, muscle, and kidney. After about three days of fasting, even the brain adapts and can obtain about half its energy from ketones. Ketones not used are excreted in urine. However, if produced in excess, they can build up in the blood. If severe in untreated diabetes, it can increase the blood’s acidity so much that normal body processes cannot proceed, eventually causing possible coma or even death.
The ketogenic diet was originally developed to treat children with epilepsy with some success. Lately, it has become a new diet trend in weight loss. When ketones are used for energy, the body can burn fat stores more efficiently often resulting in rapid body fat loss. Ketosis also lessens hunger helping to avoid excessive calorie intake.
In general, registered dietitians, but not all, do not recommend the ketogenic diet for weight loss due to some serious concerns about its safety. This is due to the lack of research especially on long-term effects. It may in some people cause adverse kidney function and bone metabolism leading to a reduction in bone mineral content. Since it is a carbohydrate restrictive diet, there may be other nutritional deficiencies that occur from a lack of fruits, vegetables, or fiber-rich foods. It is also generally a high fat diet causing some to question the safety of consuming high saturated fats and increasing heart disease risks.
There are other cautions. It is estimated that about 7 million people don’t know they have diabetes type 2. With a high number of people in the population that may have undiagnosed diabetes, the serious dangers of high levels of ketones in the blood can have serious consequences as previously discussed above.
Food choices should be monitored by a registered dietitian/nutritionist (RDN) in order to keep the carbohydrate content low and help the dieter choose healthy fats. Electrolytes such as sodium and magnesium should be assessed periodically. Lab values for total cholesterol, LDL, HDL, triglycerides, blood glucose and blood pressure should be monitored.
My opinion? Long-term use of the ketogenic diet is not recommended until more research tells us more about its safety. Perhaps it may help people to lose weight on a short-term basis; however, please consult your physician before trying any version of a ketogenic diet.
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