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So if you’re doing the most pedestrian of things, putting one foot in front of the other and just walking—not jogging, not running—are you burning fat?
Short answer is yes, walking for exercise burns fat. So if you walk “everywhere” then why don’t you look as lean as Chris Hemsworth?
The concepts of “fat burning” and “walking” have a more complicated relationship than they need to. The concept of an activity being a “fat-burning” exercise got really muddled by those charts on the treadmills at the gym that showed that slower speeds put you in the “fat-burning zone.”
The “fat-burning” zone doesn’t mean that your body is reaching into stored fat that’s accumulated around your organs or your waist, and is frying it up to serve this workout. The fat-burning zone simply refers to the type of fuel your body preferentially burns at a lower intensity of exercise. To oversimplify things a bit, the more intense the exercise, the higher proportion of carbohydrates it prefers to use for fuel (although it still likely burns some fats).
When you’re working at lower speeds and efforts, your body is taking fat molecules and turning them into fuel. It’s a time-consuming, oxygen-requiring process, and at lower speeds or when you’re just hanging out, your body is happy to primarily use this source of fuel.
As your speed and effort increases, your body needs fuel faster. It starts taking less of those fats and starts reaching more for carbs (glycogen), which is quicker burning (think kindling and newspaper instead of a gigantic log for a campfire).
So if you’re aiming to lose belly fat around your organs that can increase risk of concerns like heart disease, should you s