I truly hope you have checked with a doctor about exercixe levels and safe heart rates. 20 miles in one hour at a resistance level equal to real riding might run your pulse a tad high at your current weight. The machine at the gym might be set too low. I am for you 100%. Last spring I went from 225lb. to 195lb. in 6 months; a 1 1/4 l. a week. If I had really watched my diet and biked enough (without overstressing my body) 2 pounds a week loss would be safe for me according to the doc. I can see some reasons for the lbs plan. At the least they want your body used to being on a bike long enough to get some good out of it and to see if you have enough stick-to-itiveness before spending bucks on a good bike. Sounds like a responsible shop. Be prepared to go through two or three saddle sizes as your measurements change. Luck.