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.
Most runners have heard that running burns about 100 calories a mile. And since walking a mile requires you to move the same body weight over the same distance, walking should also burn about 100 calories a mile. Sir Isaac Newton said so.