Couple of more cents from my running coach training, and my experience as a guy.
I'll second the observation that guys put on their fat around the gut and butt. Mostly the gut. I had a furnace-like metabolism until I turned 40. Then the warrantee expired and I've gained weight over the years. 80-90% of it around the belly.
Calories in minus calories out is the way of it for weight gain or loss, with the obnoxious qualifier that your body can be very devious about changing how many calories out you get in a day. If it thinks you're in a famine, it'll drop your basal metabolism like a rock.
One generality mentioned to us in the training is that guys do better at losing weight by increasing their calories out -- exercising more. Not much progress to make by reducing calories in. There is also a tendency shared by women that if you are exercising, your body is less inclined to think that it's in a famine and drop the basal metabolism.
So the OP has a good idea in taking up some form of exercise. Anything aerobic will do. I'm partial to running, so would be happy to answer questions on that. Walking is also good, biking, cross-country skiing, and on and on. Swimming needs a little asterisk -- there's a tendency to lay in or maintain a layer of fat, more so than other aerobic activities.
A benefit for aerobic activity: among its many other good points, it is an antidepressant as effective as medications (for people with mild or moderate depression, who can maintain a fairly regular program).
Damian (and any others interested):
Running shoes should be comfortable from the first time you try walking and jogging around. Wherever you go for the shoes, be sure that they let you jog some -- at least, say, 50 yards. If they won't let you, they're not knowledgeable enough to match you up to a good shoe. (they may not be even if they do let you jog, but it's near-certainty if they don't)
Also, each maker has a wide variety of kinds of shoes. It is the type of shoe that matters more than the maker. For my running form, I need a shoe for neutral to over-pronators. I once got a shoe, from the same company, that was for under-pronators (supinators). At the time, a 10 mile run was an easy thing for me. After a single 10 mile run in those shoes, my knees were hurting. End of trying supinator shoes.
You don't need to know what supinator, over-pronator, etc. mean. But the person selling you shoes had better.
If you don't have luck finding a store near you, look for an area running club; they'll have good ideas. If you're in the US, see
http://www.rrca.org/ for a listing of clubs.
