Exercise is almost useless for weight loss. Just about every serious expert know that trying to make people exercise more, in scientific studies, has an almost negligible impact on their weight.
A new study shows a possible reason. People who are very physically active do not necessarily burn more calories than people who are moderately active. The body seems to adapt, possibly by resting more after exercising.
It may be one of the main reasons why exercise is not useful for weight loss. Exercise is good for health, strength, well-being, many things. But when it comes to weight loss, it's almost all about what you eat.
The Guardian: Exercise Alone Won't Cause Weight Loss, Study Shows Cell: Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans