Eat meat and vegetables, nuts, seeds, some fruit, little starch and no sugar. Keep intake to levels that will support exercise but not body fat.
Practice and train major lifts : deadlift, clean, squat, presses, clean-and-jerk and snatch. Similarly, master the basics of gymnastics : pull-ups, dips, rope climbs, push-ups, sit-ups, presses to handstands, pirouettes, flips, splits, and holds. Bike, run, row, etc. hard and fast
Five or six days peerweek, mix these elements in as many combinations and patterns as creativity will allow. Routine is the enemy. Keep workouts short and intense.
Regularly learn and play new sports.