The key to losing weight is not what you do, its doing it on a regular basis and sticking to it. Walking is good. Excellent in many ways. It burns off the same number of calories as running (it just takes you longer to do it, but a mile run and a mile walk are about the same in caloric output), its low impact, and its very human.
You just have to set out time and do it on a constant basis. And vary it. Most day's you'll walk say a couple of miles, once a week, do two or three times that, and take a day off for rest too. Or to do something different.
I like biking, and I ride all the time, but I do that for conditioning more than anything, of course I tend to ride to the next town on a wandering path go to a brew pub there for a spell, ride back, meander some more, and stop at my favorite brew pub a couple of blocks from my house when I'm done - say about 20 miles in all, so its not like I'm losing weight with that regime.
For muscles, depends on if you want them toned, or if you want guns. For toning, light weights at a high level of reps, for bigger muscles, progressively heavier weights - like to the straining point - fewer times.
And you do have to watch the food. When I have like 20 shows in a month, and that's 20 trucks to load, and unload, and 20 shows to set up and run (and I've put a pedometer on myself and I can walk 25 miles on a show day) I still gain weight because of the backstage food deal.