Is it heresy to believe in the evolution of the human body?

Yes, in this sense. In Humani Generis of 1951, Pius XII permitted Catholic scholars to study evolution but set one hoop they must pass through: no Catholic may believe in polygenism. Polygenism means many first generations, thousands of Adams and Eves emerging from apes across the world; monogenism means one first couple, Adam and Eve, from whom every generation descends. This matters because the Church teaches that original sin began with one first couple and is passed down to all their descendants. If there were many first parents, then only one couple could have committed the original sin, so the others would not have it, which shatters the doctrine. From 1951 to today, no one has been able to reconcile polygenism with the doctrine of original sin from monogenism; Jimmy Akin's attempt is, frankly, laughable. No pope has yet formally declared evolution a heresy, but Pius XII's requirement is nearly as good, because it puts the ball in the evolutionists' court, and they have never answered it and never will. So in that sense it is a heresy.