Read recent headlines or scroll through your social media feeds and you’ll likely see people talking about “keto” diets and keto-friendly recipes. This popular diet has gained attention for a variety of reasons ranging from weight loss success stories to the unexpected body odors some people on the diet experience. If the term “keto” is new to you, you may wonder what it is and if it’s dangerous or beneficial to your health. Read on for a breakdown.
Ketogenesis happens when we burn our own body fat to use as fuel. When fatty acids break down, they produce a molecule called acetyl-CoA that the liver uses to make what are known as ketone bodies. Being “in ketosis” means you have high levels of ketone bodies—sometimes simply called ketones—in your blood because you’re burning body fat instead of carbohydrates. Ketosis can be dangerous for some people, especially those who have diabetes.
Ketosis may have evolved as a survival mechanism when food—especially energy-rich carbohydrates—was in short supply. Without food as a source of incoming energy, blood sugar (glucose) levels decrease. Glucose is the preferred fuel source for most body tissues when it’s available. But during periods of starvation, energy must come from elsewhere; otherwise we’d be unable to function and would eventually die. Historically, ketosis was a way to produce energy by using stored fat to feed the brain, heart and muscles. Ketones likely helped hunter-gatherers avoid an energy drain so they could, well, hunt and gather.
Ketosis was—and might still be—beneficial. But today, we rarely experience carbohydrate deprivation or go more than a few hours without eating. For this reason, people are turning to ketogenic diets to boost their body and brain.
A keto diet is a more extreme version of a low-carbohydrate, high-fat diet. Seventy-five percent or more of its total calories comes from fat and 20 to 30 percent comes from protein. You’ll eat a meager amount of carbohydrates on a keto diet. Think heavy on oils, eggs and cheese and low on spaghetti.
Despite the fear many people may have of eating too much fat, ketogenic diets are being used to treat metabolic disorders. A recent article in the American Journal of Physiology—Regulatory, Integrative and Comparative Physiology found that a low-carb, high-fat diet lowered blood sugar in people with type 2 diabetes.
A ketogenic diet might also increase the expression of genes involved in fat burning, blood sugar regulation and the amount of energy we expend. These changes also occur with exercise and fasting. Another popular claim is that ketosis is a “magic pill” that improves mental clarity and energy levels. While this theory has not been studied, ketosis is a natural physiological function we evolved with that helped our ancestors survive and might enhance health in the 21st century. With that in mind, further study may be worth exploring.
Brady Holmer is a PhD student in exercise physiology at the University of Florida. His lab focuses on cardiovascular physiology; mainly how exercise can play a role in health, disease and aging.