Back in the day I rode 4K miles in 60 days and lost maybe 2 pounds at the most and being 5' 10" and 155 (and a soccer playing, running, paddling fool)...I didn't have a lot to lose. I'd bet cyclocross and MTB'ers are lighter than roadies in general. Also, smartphone apps overestimate caloric burn and likely BMR. All things considered, I'll lose weight riding 80+ miles a week, maintain weight at 50 miles a week and gain weight sub 50 miles per week. Keeping an eating journal (aka My Fitness Pal or similar) and logging everything...and running a 200 calorie daily deficit...you'll lose weight. Many older athletes struggle with cycling efficiency and the time commitment because...they are used to running and when you go non-load bearing as noted above...gotta put the hours in! I'm heading for the hills (is it possible BF is contributing to my lazy ass Saturday morning?).