Depends on the elevation gains in your 100km ride but I think that 3,300kcal for a 100km/4h ride is generous.
800kcal/hr is hard work and keeping that up for 4h is even harder. 25kph does not sound like 800kcal/hr unless there was some reasonable elevation gains. I’d expect at least 1000m elevation gain over that 100km for those numbers to at least approach something sensible. If it was a flatter ride than that then Strava is just lying to you.
But, yes, long distance cycling is an awesome way of burning calories. When I used to do Brevet/Audax riding I was the closest to my old teenage weight as I have been in the last ~30 years.
[1] https://en.wikipedia.org/wiki/Bicycle_performance#Total_powe..., https://www.road-bike.co.uk/articles/cycling-power.php [2] https://www.quora.com/How-efficient-is-the-human-body-at-con...
Being someone who has a power meter, I can say that strava's estimates over a long time period aren't that terrible, but if you're riding in a group, or there was a some wind, or a million other reasons they can be absolutely miles out.
That's hardly strava's fault, it's more about what's actually possible with an estimate.
What is completely made up and should be ignored is the calorie burn estimates you get from gym equipment.
Strava’s calorie estimation is awful.
> I’d expect at least 1000m elevation gain over that 100km
1% average grade is pretty mild. I'd bet OP did at least 3000m to get those numbers
And one doesn't have to do 100km all at once. A 10km commute each way over a 5 day workweek is a much less intimidating prospect.
Now I live in America need a car :(
> Now I live in America need a car :(
Why? Are there even longer distances?
I was doing it on a roadbike and could comfortably average 27km which got me there 3h. Driving was about 1.2h.
In the summer, I would start pedalling at 5am and get to a local cafe at 8. The first hour was amazing, broad daylight and you basically had the whole road network to myself.
It could depend on how you define "almost 100%" of course. There's a big difference between 5% and 0.001%.
NB nobody would be able to do this without ingesting a substantial amount of food during. If you didn't start eating hourly after about 1-2 hours in, you'll "bonk" or run out of glycogen.
After a few years of regular (monthly) 200km rides I could do a 200km ride (~10h elapsed) without eating anything on the way round.
Cycling at 15mph on flat ground is pretty easy. If you can do that for an hour, and can progress at 10% increase in riding time week over week (pretty reasonable for someone who is still gaining fitness from "nothing"), you'll be doing four hour rides after just 16 weeks.
that said, ok, 15mph is not that easy -- maybe starting more like 10mph on a road bike for an hour would be more reasonable.
I still think most able bodied people could get to OP's fitness in much less than a year.
One data point - I was horribly out of shape in my mid 20s and got to riding 4 hour/15mph about four months after I bought my bike. But I was also unemployed for about a month of that!