“If someone says you can lose 20 pounds in the course of a year by punching a bag, then I’m signing up,” says Stephen Stoute, the 39-year-old chief executive of Carol’s Daughter beauty and skin-care line. “There’s a Rocky in all of us.”

Mr. Stoute did just that—except he dropped nearly 100 pounds over the course of nine years.

Mr. Stoute was in top shape in his teens and early 20s, playing football in both high school and college. “Once I got into the professional world, health was not at the forefront of things on my mind,” says Mr. Stoute, who was executive vice president of Interscope Geffen A&M Records. The pounds slowly started to creep on and by age 30 he weighed 315 pounds.