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.
Individuals who successfully loss weight and keep it off burn about 2,800 calories a week through planned exercise, according to statistics from the National WeightControl Registry. Assuming an average of 100 calories per mile, that's about 28 miles, so make that your goal if running is your only form of exercise.