If you make the right meal (and drink) choices, get enough sleep, and do resistance training (to boost calorie burning), then, yes, three hours of cardio a week should do it.
While you’re at it, try these tweaks to ignite extra fat burning:
Do 30–60 minutes of cardio at a time.
Keep your heart rate at 65–85% of your anaerobic threshold but spike it with higher-intensity intervals.
I’d say daily, so it becomes routine. But bottom line, do what fits your schedule without adding stress—that raises cortisol, causing your body to hoard the very fat you’re trying to jettison.
Just be consistent and have fun with it, because there’s simply no getting around having to do it!
Gunnar Peterson is a celebrity trainer and columnist for Men's Fitness. Follow him on Twitter.