be careful to eat enough carbs to cover your high volume or you'll get overtrained/sick... i didn't realize you were 240! That's like me slapping an 80lb weight on my back, i'd barely be able to pedal. As your weight drops you'll be flying. I know some big dudes who are monsters on the flats... a local cat 2 is 210lbs and he'll take a pull into a headwind that drops everyone within a minute. On a small hill he can use his power to go up in a huge gear and then I have to pedal just to stay in his draft on the way down.
plugging some rough estimates into a
calc for you:
30 miles, 160 watts (estimate) and no hills:
240lbs @ 160w: 16.93mph
200lbs @ 160w: 17.17mph
Now add 20 watts for improvement (still a realistic increase for you) to the 200lb effort and make it a
1% grade hill:
240lbs @ 160w: 13.37mph
200lbs @ 180w: 15.05mph
Some more fun:
my best estimate of your 5miles avg power might be 205w
on a 5 mile hill @ 3% you'll go up it 3 minutes (!) faster at 200lbs with the current power.
What I'm getting at is that even though 240 is high now, if you keep riding and improving as you drop some weight you'll keep seeing "huge gains" for a
long time. Constant reward.
For weight loss the LONG (3+hour) group rides at ~70% can melt the fat while not being nearly as boring as riding alone. Intensity is low enough that you don't have to cram the carbs, just try to take in 2-300 cals of carbs an hour and then fight like hell to not binge that night. Eat the biggest breakfast you can manage before, too.
The best thing you can do is find a club to ride with. Second best thing is fork control :-P
