A slow, low-intensity run uses more fat for fuel but takes longer to burn a lot of calories in total. That’s why it’s advised to run longer than 30 minutes when running at a low-intensity. However, a faster, high-intensity run can burn more calories in a shorter time period. And even if just a small percentage of those calories come from fat, it can still significantly boost your weight loss!
The prevailing formula for a long time on how much fat you’re going to burn was calories in minus calories out, based on your basal metabolic rate (BMR) and exercise efforts, explains strength and performance specialist Joel Seedman, Ph.D., owner of Advanced Human Performance in Atlanta. But with all the different biochemical reactions in the body, hormonal response, and endocrine function, there are an infinite number of factors that can affect how your body is storing and breaking down calories.