With obesity rates continuing to rise, gyms are turning to the newest population of would-be exercisers: children. The programs are a welcome substitute for school-based physical-education classes, which are among the first to be sacrificed when budgets shrink. Thanks in part to First Lady Michelle Obama’s Let’s Move campaign, which encourages youngsters to become more physically active, child-focused gyms and wellness centers are hoping to build good exercise habits in kids so that they’ll become part of a lifetime routine. Teaching children about the importance of exercise early on can help make them fitter adults, which in turn might finally lead to a drop in chronic diseases such as diabetes and heart disease.