Thanks for the reply, and the advice. And I'm male.

tbh, I don't think I was eating properly prior to starting the cycling. The cycling is probably amplifying the effect. I'd like to lose some fat, and build some leg muscle/stamina, so I've been adding some 10 mile cycles at the weekend, just to get started. I'm finding the 7km/20minute commute cycles are getting 'too easy'.

In the mornings I'm eating a banana before the cycle, and ham/chicken/cheese/meat for breakfast after the cycle. I try to have a light lunch, and before the evening cycle I have mostly fruit salad.

And yes, lots of endorphins, as I'm getting a good kick out of cycling, mixed with adrenalin, due to cycling on city streets... ;-)