Well I'm impressed. It's probably because you were already (before starting to run) pretty fit, seeing how you bike so much. Before I started running I was someone whose only exercise was walking to campus, so in the first few days I found even half a mile (maybe even a quarter due to cramps) to be a problem.
I suggest following the c25k program, for new runners:
http://www.coolrunning.com/engine/2/2_3/181.shtmlI did up to week 4 day 1, then got bored and just started doing 2-3 miles.
Damn. Rough. Seen a doc for ... what ... hypothyroidism?
No, but it's a family trait for sure. Everybody on my mom's side of the family has the same overall shape. I have one uncle who runs and managed to keep somewhat slim, but everybody else is well overweight.
The way I look at it, though, is that if I can bike 50km+ and run 4km+ without a whole lot of training, I must at least be in decent shape, even if I don't look it. So I take solice in that.
Next time I go for a checkup, though, I'll definitely talk to my doctor.