There are a lot of wonderful things about summer that make it easier to stick to a healthy lifestyle: The nicer weather makes heading outside for a walk, bike ride or swim more tempting; fresh veggies are abundant and affordable at roadside stands and farmers’ markets; and dessert is easier (and healthier) than ever thanks to the availability of ripe, fresh, sweet fruit! Of course, there’s room in our diets for the occasional piece of pie or fudgy brownie, but for…