They are in practice true. When people imagine exercising to lose weight, very few imagine that this implies running at a moderate pace for nearly 4 hours per week (while also holding diet to maintenance levels) to lose just 1 pound per week.

The real kicker is that an unchecked diet will offset virtually any amount of exercise. An unchecked diet means people will feel hungrier after exercise and thus eat more. It takes a lot of exercise to reach the point that it manages to outrun appetite and bad eating habits. There are a lot of fat people who work physically demanding jobs.