What Ketosis Actually Means When You're Following A Keto Diet

Unless you've been living under a rock for the better part of the last decade, you've heard about the keto diet. Fans tout it as a relatively quick and easy weight-loss program. Detractors argue the high-fat, low-carb eating plan is inherently unhealthy, even dangerous.

A 2021 statement released by the Physicians Committee for Responsible Medicine cites the findings of a report published by Frontiers in Nutrition listing key concerns about ketogenic diets including potential risk of neural tube defects in developing fetuses, increased risk of kidney failure among the kidney-compromised population, a rise in LDL (the so-called bad cholesterol), and greater risk of diseases including heart disease, cancer, diabetes, and Alzheimer's.

At the other end of the spectrum, a 2019 report by The New York Times references the experience of University of California preventive cardiologist Dr. Ethan Weiss, a long-time keto skeptic turned proponent. In an effort to gain a better understanding of why ketogenic diets were becoming so popular, Weiss decided to try the eating plan he so vehemently opposed. He lost 20 pounds and told The New York Times, "I haven't felt this good since I was in high school."

According to Healthline, ketosis refers to a metabolic state in which the human body switches up the way it produces energy, relying on fat instead of carbohydrates for fuel. It's the opposite of gluconeogenesis, the body's default mechanism for producing the glucose that fuels our cells (via Very Well Fit).

A ketogenic diet jumpstarts that switch by depriving the body of carbohydrates to produce glucose and forcing it to burn fat to make ketones, an alternate source of fuel. According to the Mayo Clinic, a typical American diet usually includes at least 50% carbohydrates. In contrast, a keto diet breaks down to about 75% fat, 20% protein, and just 5% carbohydrates (via Bolst Global). The Mayo Clinic acknowledges the eating plan can lead to weight loss, but cautions it can take up to three weeks for ketosis to kick in and start burning fat.

So how do you know when you're in ketosis? You'll begin to notice a few signs — and some are less than pleasant. Monitoring blood and urine samples is one sure way to test for ketosis, according to Medical News Today. Additionally, the growing popularity of keto diets has spurred the development of at-home tests, like breath analyzers, to test ketone levels. In addition to weight loss, physical signs to note may include increased thirst, muscle cramps caused by dehydration and electrolyte imbalances, headaches, fatigue, and bad breath. On the plus side, enhanced clarity and more focused thinking can be indicators of ketosis.