Exercise = Weight Loss, Except When it Doesn't 

This article goes to a lot of effort to defend the concept of calories as an useful measure of exercise. I have difficulty with a lot of fitness articles that make claims without any scientific rigor. Another straw man presented in this article is the claim that gravity-based exercise, such as walking, gives a better workout than supported exercise, like swimming. On reflection, that should seem ridiculous, as the benefit one gets from exercise is proportional to the amount of work the muscles perform, and the work is largely based on resistance. Since swimming does not eliminate gravity - you still have to work against gravity to stay afloat - and the resistance of water is greater than the resistance of air, you're dealing with much more resistance swimming than walking...*if* you are trying to work your muscles. A swimmer pushing himself to speed is going to work a lot harder than a speed walker, but a person doing lazy laps might just work less than a person walking briskly to the store.