Some people trying to lose weight will rely on calorie expenditure tables to figure out how many calories they're burning while running or doing other physical activities. The problem is that those tables tell you the calorie expenditure of an average person and usually overestimate the calorie expenditure. The same is true for treadmills and other cardio machines that display calorie expenditures. Some reports suggest that treadmills and other cardio machines actually overestimate calories
burned by up to 15% to 20%.
How to fix it: It's important that you take calories burned estimates with a grain of salt. It's fine to use the numbers as a benchmark for your runs, but don't plan on consuming additional calories based on that number. That's an easy way to start gaining weight, despite your exercise efforts. If you really want to get a better idea of how many calories you're burning during your runs, try using a heart rate monitor. That will be more accurate than relying on tables or cardio machine readings.