Does Running on a Low Carb Diet Burn Fat Quicker?

When you follow them successfully, low-carb diets make your body switch from using glucose as its main source of energy to using fat. When you exercise, your body prefers using glucose to fat or protein. However, if you are following a low-carb diet, your stores of stored glucose are depleted, so the body is forced to break down fat to produce energy for the exercise.

Glucose Metabolism and Exercise

Your body needs energy to function and requires additional energy to perform exercise. It produces this energy by converting dietary nutrients or stored nutrients into energy in the mitochondria, the cells’ engines. If you eat before exercising, the body will convert glucose from that food into energy. If you exercise on an empty stomach, your pancreas will secrete the food-metabolizing hormone glucagon. When this hormone binds to cell receptors, it signals to the cells that energy is needed. The cells respond by releasing glucose into the bloodstream. The muscles can then absorb the glucose and convert it into energy. Muscle cells also have their own stores of glucose that they can convert into energy.

Prolonged Exercise

After exercising continuously for an extended time period, you deplete your stores of glycogen, the stored form of glucose. At this point, the body will switch from using glucose as a fuel to using fat. Fat cells store fat in the form of triglycerides. When the body requires energy from fat, stored fat breaks down into glycerol and fatty acids, which can then convert into energy in the muscles. Glycerol and fatty acids are a more efficient source of energy than glucose, yielding about twice as much energy per unit.

Low-Carb Diets

Low-carb diets deplete the body’s stores of glycogen. Once the stores of glycogen are depleted, the body uses fat as its main fuel. This metabolism mode is also known as ketosis or the fat-burning mode. To enter a fat-burning mode, the calorie intake must be lower than the calories the body uses. However, because fat and protein are more filling than carbohydrates, successful low-carb diets naturally restrict the calorie intake without the dieter having to actually count calories.

Running with Empty Sugar Stores

When you run while observing a low-carb diet, your stores of glucose are already depleted. So, the energy your muscles need to carry out the exercise comes from fatty acids and glycerol released from fat cells. Though fat is a more efficient source of energy than glucose, it is also more difficult for the body to turn fat into energy. So, exercising while following a low-carb diet may lead to exhaustion, especially in the initial phases. Once the body gets into the habit of using fat rather than glucose as an energy source, the exhaustion normally goes away.