Walking is often viewed as a simple, low-impact exercise, and many people wonder how it affects the body’s energy stores. Yes, walking does burn carbohydrates, but not in the way that a high-intensity workout does. The body uses two primary energy sources during exercise: fat (stored as triglycerides) and carbohydrates (stored as glycogen). Walking contributes to your total energy expenditure by utilizing a mix of these stored fuels.
How the Body Chooses Fuel Sources
The immediate energy currency for all muscle action is Adenosine Triphosphate (ATP), which must be constantly generated to sustain activity. The body uses both fat and carbohydrates to create ATP through different metabolic pathways, and the selection of which fuel source to prioritize is governed primarily by exercise intensity.
At rest, the body is highly efficient and uses mostly fat as its energy source, contributing approximately 85% of the total energy production. As exercise intensity increases, the body requires ATP faster than fat metabolism can provide, since fat oxidation is a relatively slow process. This shift is known as the “crossover point,” where the body transitions from using fat as the predominant fuel to relying more heavily on carbohydrates. This transition typically occurs around 30% to 40% of an individual’s maximum oxygen consumption (\(\text{VO}_2\text{max}\)).
Carbohydrate Use During Walking
Since a typical walk is low-intensity, steady-state exercise, it generally occurs below the metabolic crossover point. This means the majority of energy expended during a moderate walk comes from fat stores. For example, at an intensity around 20% of \(\text{VO}_2\text{max}\), roughly 60% of the total calories burned come from fat.
Despite being fat-dominant, walking still requires a continuous supply of glucose, the simplest form of carbohydrate. Carbohydrates stored as glycogen in the muscles and liver are used to sustain the metabolic process and provide fuel for the central nervous system. This reliance on fat at lower intensities allows for “glycogen sparing,” meaning the body conserves its limited carbohydrate reserves for higher-intensity effort. The body always burns both fuel types simultaneously, but the percentage derived from carbohydrates remains relatively small during a standard walk.
Strategies for Increasing Carbohydrate Burn
If your goal is to increase the proportion of carbohydrates burned, you must increase the intensity of your walk to move closer to the metabolic crossover point. The faster energy demands of higher intensity exercise necessitate using the quicker carbohydrate pathway. Increasing your walking speed to a brisk pace, where it becomes difficult to talk in full sentences, is one effective method.
Incorporating periods of greater effort, such as walking up hills or adding short bursts of fast walking, can dramatically increase carbohydrate utilization. This type of interval training forces the body to temporarily rely on anaerobic metabolism, which uses carbohydrates almost exclusively. Adding an incline engages more muscle mass and elevates your heart rate, pushing your body past the fat-dominant zone. Alternating between speeds has also been shown to burn up to 20% more total calories than maintaining a steady pace.
The Role of Total Calorie Expenditure
While optimizing the percentage of carbohydrate burn can be useful for certain fitness goals, the total number of calories expended remains the most significant factor for weight management. High-intensity activity burns a greater proportion of carbohydrates, and it also burns significantly more total calories per minute than low-intensity activity. This means that even if a higher-intensity effort uses a lower percentage of fat, the total amount of fat calories burned may still be greater because the overall energy output is higher.
Focusing solely on the “fat-burning zone” can be misleading, as the goal for managing body weight is creating a sustained calorie deficit. Walking, even at a moderate pace, is an effective tool for increasing your total daily energy expenditure and contributing to this deficit. The total duration of a walk, combined with its intensity, determines the final caloric burn, regardless of the precise fuel mix used.