I am 51 1/2 years old
not over weight... by much... but at 5'10, I was up to 185, and had been slender all my life (165 would make me happy again)
When I started to bike commute regularly (17 miles round trip over relatively flat terraiin with a couple modest hills) I started to see weight moving down ... about 8-10 pounds over a 6-8 month period... of fairly regular (not daily) commuting. Each way it takes about 35 minutes... and I keep a good pace (12-14 mph). So... 2 x 35 minutes a day, 2-4 days a week.

This is key... regular pace, regular exercise. Yogurt and granola for breakfast... and don't pig out (cept for some Friday brews!)

If I get busy (having to drive due to errands) the weight returns.
This year I am going to bike the bullet and try to commute as much as possible in nasty weather... so activity is year round.