First, I would suggest that anyone who is looking for a good in-home workout check out the comments to the last post. The Woulfes recommended "Never Gymless" by Ross Enamait as a resource of exercises that don't need equipment. I knew there would be one out there, that is probably a better way to go than my thoughts expressed on a blog.
Then Emily asked the question that I wanted to answer next. Yes, running is the way to lose fat. I'll got into more detail. I'm going to write about running today, but what I really mean is aerobic exercise. The best aerobic exercises are repetitive movements of large muscle groups. Cycling is my favorite, but running, walking, rowing, cross country skiing, in-line skating, and swimming would also fit the bill. The thing is, all you need to run is shoes, so I'm going to write from a running perspective, but keep in mind that any aerobic exercise would work.
The key to fat loss is burning more calories than you consume. The American College of Sports Medicine says to participate in 30 or more minutes of moderate intensity aerobic exercise most if not all days of the week. That would mean at least four days a week. I think that is good advice.
Moderate intensity and 30 minutes or more are getting to the idea of duration and intensity and I think those points need to be discussed together. The faster you run, the less time you will be able to endure the torture... I mean running. Also note, that the faster you run, the more calories you will be burning. The slower you run, the fewer calories you will be burning, but the longer you will be able to run before exhaustion.
Do you know those little charts they have on exercise machines that show the "fat burning zone"? Forget everything you know about them, they're dumb and misleading. It doesn't matter if you are burning fat or carbohydrates, if you burn more calories than you consume, in the long run that will come from your fat stores. Sure, you may burn some protein from muscle and you may deplete glycogen (carbohydrate) stores, but the carbohydrate stores will return when you eat and the protein... there's not much you can do about the protein except weight training. So do that.
If you go and do wind sprints (10 second sprints with 30 seconds of rest repeated for 30 minutes), you will burn almost entirely carbohydrates. If you sit on your couch watching television, you will burn mostly fat. The difference is that the wind sprints will burn a lot more total calories. The next time you eat after the wind sprints your body will replenish carbohydrate stores with the calories in the meal, and use fat stores to provide you energy while it is replenishing carbohydrate stores. Eventually, caloric deficit will lead to fat loss. That's just how it works.
I still haven't addressed how long and how hard. How about this. Run for 30-40 minutes and when you are done you should be completely spent. So find the pace that you can barely maintain for 30-40 minutes. If you really want a heart rate to go along with it, look it up on the internet, it's around 70-80% of your max heart rate. If you don't have that much time, run faster. If you have more time, or need to get somewhere, walk instead of driving.
Emily asked if it was OK to walk, as long as you keep your heart rate up. No. Well, I mean it's fine to walk, I'm not trying to be a nasty drill sergeant that is just mean, but running burns more calories. When you are running, you're burning lots of calories. When you walk, you are burning fewer calories, even if your heart rate is still up. Run as much as you can. Or walk briskly. Here's the thing. The harder it is to do, the more calories it is burning. Sorry, you just can't get around that.
As an interesting aside, I've seen a study that showed that the greater the energy flux, the better the body is able to accurately gauge energy intake with hunger. That means that the more energy you are expending with exercise, the better your body is at regulating how much you eat, without you having to think about it.
4 days a week of aerobic and 2-3 days a week of resistance training would be a good mix.
I have to go do something now...