Calories lost on the ride is probably about right but like you I weigh myself before a ride--And if it was a hard or hot ride- I weigh myself afterwards. Any weight loss I put back on with fluids and then carry on for the rest of the day. Weight loss during a ride is most likely Fluid and IF I don't put it back on by drinking after the ride- then I have a thirst for the rest of the day that is difficult to get rid of. I eat lightly for the rest of the day and next morning usually find there is no weight loss but providing I don't pig out on buns and pies then the weight will come off over the next few days.

But I am lucky in that I am not trying to lose weight. I am at 140 lbs and may go up to 144 with less exercise and more eating. I recently did a ride and 142 in the morning--137 after an easy 50 miles but with heat and over 5 hours. Drank to get back to 140 and without cutting food or "Extra" exercise was still 140 5 days later. But at the start of the year I was 155lbs. That did take some serious Exercise and a very good look at my diet. The extra 15lbs came off in about 4 months and luckily I have kept it off

I stress that I am trying to keep my weight steady and not lose weight so my regime will be different to someone trying to lose weight. If I was it would be Use 2,000 calories- eat 1500. And eat the right food that will not give a weight gain--No fats- no sugars and cut back on carbs.