Balancing life/knitting/exercise

I admit it -- I've gained 25 pounds in the 2-1/2 years I've been knitting, and all this sedentary inactivity is getting to me. (What, you mean knit one-purl two isn't aerobic?)
I used to be a bit of a gym rat; or at least I've had spells when I was at the gym, or doing something active, once or twice a day. I did a triathlon in '05, and even though I think I had the slowest time in the history of the event, I won my heat in swimming (against two other slow people, but they weren't old and fat!) and I did finish. The toughest part was the run, 3-plus miles of hilly, rocky torture that might have been scenic from, say, a stretcher or the back of a pack mule. I hadn't been able to train for the run much because of persistent leg cramps, and race-day was no exception. So I basically half-trotted, half-limped through that final stretch. The triathlon happened to be a qualifying event for the Senior Olympics, and the oldest participant, an 83-year-old woman, passed me on the trail. I swear to God she would've gone down if I'd known she was sneaking up behind me, but lucky for her I never saw her coming.
Anyway, since the advent of my needle addiction, life has changed. Instead of running, swimming or biking, I've been concentrating on lace and hats and shawls and scarves.
Rolling a skein of yarn into a ball gets me out of breath, and the closest I've come to weight-training is lugging around an obscene number of bags overflowing with yarn to suit any exigency. Like, for instance, if I happened upon an entire class of preschoolers stranded in the snow without mittens. Or if one of my kids called and said, "Mom, I need you to knit matching hats and hand mitts for everybody in Chicago." Really, you have to be prepared for these things.
You'd think that sheer dedication alone would be enough to scare the nasty beastie pounds off. But no. They say that loved ones grow to look like each other. And so perhaps that is why I've grown rounder, and softer, and fluffier, comfortably smooshy like my knitting chair.
Still, enough is enough. I am intent on reversing the trend, to resembling the strand of yarn more than the fat round yarn ball.
I'm not going to do silly tricks like vowing not to knit any given day until I've worked out. Games don't work for me. I've rejoined Weight Watchers and lost 5 pounds so far. And I am going to make sure I get myself to the gym, or out for an hour with Bandit, five days a week. I'll keep track of my progress here, and maybe that'll help keep me honest. So here goes...
Activity today: Gym
Knitting today: Sock-blank socks. I'm way behind everybody else, most of whom finished their socks months and months ago. Hope I can figure out how to do the heel etc. doing two socks at once on one circ!