Definition of organism for English Language Learners. : 1  an individual living thing. : 2  a system with many parts that depend on each other and work together.
Figuring out how many calories you burn when running is, on a simple level, a fairly straightforward calculation. Most experts (and lots of studies) suggest that a person of average weight burns about 100 calories in a mile of running.
Many people believe that running and walking the same distance burns the same number of calories, but that isn't true. A 2004 study in Medicine & Science in Sports & Exercise found that the average female participant burned 74 calories when she walked 1 mile, but 105 calories by running the same distance.