While intense exercise will take off the weight, especially moderate to intense cardio, a healthy diet used in conjuction to the exercise would help them drop the pounds even faster. If there is absolutely no getting them to eat less (we all know how stubborn some guys are); intensive cardio exercise, given that they're healthy enough to jump into that activity level, is a very effective way to drop the pounds. In order to keep the pounds off however, strength training exercises, along with a general diet reduction will allow a great body without anywhere near the upkeep that would be required from a bad diet and sedentary lifestyle.