"Research indicates that people actually underestimate the amount they eat by about 40 percent if you are overweight and 20 percent if you are at a normal weight," Albers says. It's true that exercise does give us a little more leeway to splurge, but keep in mind that a three-mile run (at a quick pace—10 min/mile) will take you 30 minutes, and you'll burn about 307 calories (based on a 135 lb. woman). That's about the equivalent of a grande Green Tea Frappuccino.
Bushard adds that this strategy can actually hurt your workouts, saying that "by splurging (normally with sugary foods) you’ll increase inflammation and slow down recovery."