Ketosis, Weight Loss and a Low-Carb Diet

A low-carb diet comes with a great weight-loss aid: ketones. In this introduction to ketosis and weight loss, learn how protein and fats fuel body needs.

A low-carbohydrate diet brings many misunderstandings. While dietary ketosis does correct metabolic imbalances and ushers in the blessed state of satiety, confusion exists regarding its place, safety, and role in diets for weight loss. Carbohydrate restriction is only one of many possible solutions. It does not work for everyone. Often chosen due to its quick fat-loss claims, understanding ketosis, weight loss, and the myths that surround ketones is vital to the diet’s success.

Most Weight-Loss Solutions Focus on Normal Metabolism

Most diets focus on calories. For those with a normal metabolism, lowering calories works well. The body uses four different types of fuel depending upon current metabolic needs: glucose, protein, fatty acids, and ketones. All diets (including low-carb programs) switch between these fuels depending on current energy requirements.

When glucose is available, it is burned first. What is not immediately needed gets shuttled off to the liver which converts it into glycogen, the body’s storage form of carbohydrates. Glucose is not turned into body fat unless glycogen stores are full. The idea that overweight comes from eating too much holds true. What the body cannot store in the liver and muscles converts into triglycerides and becomes body fat.

However, storing glucose is a normal metabolic function. Glucose only causes excess body fat when a person eats more than needed for energy purposes, body repair, and glycogen storage on a regular basis. Setting up a low-calorie diet for weight loss is a good solution for those with a normal metabolism.

Carbohydrate Restriction Focuses on Ketosis and Weight Loss

A low-carb plan focuses on the ketosis-metabolic pathway. The liver stores more than enough glycogen to keep the blood glucose level stable, but severe carbohydrate restriction uses up that safety net within a single day. Since triglycerides cannot be turned into glucose (only the glycerol molecule attached to the fatty acids), when supplies begin to run low, the liver hunts for protein it can break down into the type of amino acids needed. This process is called gluconeogenesis.

There is nothing unusual about using this pathway. Many low-calorie diets contain fewer carbohydrates than a typical American diet and work in a similar manner. The difference is that carb restriction programs typically focus on the ketosis-metabolic angle exclusively. Unfortunately, many low-carb authors and dieters downplay the role of calories in weight loss. For some individuals, ignoring calories and overeating dietary fats has caused their low-carb diet plan to stop working.

Fat-Burning Metabolism as a Weight-Loss Aid Misunderstood

High levels of ketones are thought to exclusively create a fat-burning metabolism resulting in quick fat loss. Often low-carb dieters refer to this process as the body switching from a glucose-burning metabolism to a fat-burning one. This is a misunderstanding. The body uses whatever fuel source is available at the time; high levels of ketones in the blood do not change that.

When carbohydrates are reduced, the glucose produced from vegetables and other carbohydrate sources take precedence immediately after being eaten. Momentarily these sources of glucose turn the dieter temporarily back into a glucose-burning metabolism until those carbs are used.

What are Ketones? How is a Low-Carb Diet Fueled?

When glucose runs short, most of the body’s tissues can use fatty acids for fuel, including the liver, but not all of them. The brain, red blood cells, bone marrow, some muscle and kidney cells need glucose. According to Dr. Michael Eades, author of The Protein Power Lifeplan, "Metabolism and Ketosis,” glucose needs amounts to about 200 grams of sugar per day. To fulfill this need, the liver uses protein sources.

With severe carbohydrate restriction, eating enough protein is essential. If a dieter ignores this important nutrient, the liver will take what it needs from the body’s protein stores: the muscles. However, there is a back-up system for needed glucose, though it takes time to implement. To get the caloric energy the liver needs to break down proteins, it uses stored triglycerides or dietary fats. When triglycerides are broken down into fatty acids for fuel, Ketones are a by-product that results.

Ketones are always produced when triglycerides are broken down, even on a low-calorie program. Since most body tissues can use ketones for fuel, this initial state of ketone use is often held up by low carbers as being the ultimate magic that drives the quick weight loss seen on a low-carb diet. However, once the body adapts to using ketones, other body tissues switch to using fatty acids exclusively. This saves ketones for the brain’s needs and cuts the body’s overall glucose and ketone requirements tremendously.

Understanding Ketosis and Metabolism

Understanding the process of ketosis and what actually creates a low-carb metabolism is essential to the diet's success. For example, one of the most common misunderstandings regarding ketosis is dietary fats. Dietary fat has nothing to do with getting into the state of ketosis. Ketones are produced when glycogen stores get too low. At that point, the liver uses stored body fat, or dietary fats, to convert amino acids from available protein into glucose. Diets always require an individual to eat less than their body needs; low-carb plans are no different.


Atkins, Robert C., MD, Dr. Atkins’ New Diet Revolution, M. Evans and Company, Inc.

Eades, Michael, R., MD and Eades, Mary Dan, MD, The Protein Power Lifeplan: A New Comprehensive Blueprint for Optimal Health, Warner Books

Eades, Michael, R., MD, “Metabolism and Ketosis

McDonald, Lyle, The Ketogenic Diet: A Complete Guide for the Dieter and Practitioner, Lyle McDonald

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