I figure about 300 per hour while cycling (of course, everyone is different), but for long distance, your body chemistry changes. Not sure, but it might be better to increase the protein ratio towards the end. (That's what I do, there is probably a good scientific article on the internet somewhere, may completely contradict that.
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It also matters what your body type is., Mesomorph, Endomorph, Ectomorph, bone structure, etc. I'm a mesomorph (naturally more muscular) with heavy bones. And I'm 5'7'', so my baseline calories are higher than someone whose ideal weight is lower. (Mine is about 150, maybe down to 145 if I want to go extremely lean).
I figure (and some disagree, plus, body-type matters) my current weight times 12 to maintain current weight. So, 150 X 12 ='s 1800 calories per day. That is without exercise. With exercise would be 1800 per day plus however many per hour of cycling.
For a short, 1 hour ride at speed, I add about 300 calories, total. Someone who is more petit might have a much higher metabolism, so that 12 could be a 15. And my metabolism tends to increase as I get leaner, mostly because I'm exercising more, I think. But perhaps also I'm burning faster when I weigh less. (Seems like it, anyway). If I wanted to lose weight, I'd subtract 3500 calories per week from my diet, or 500 calories per day (not including ride fuel). One pound ='s 3500 calories. So, 1800-500=1300 calories per day with no exercise should, theoretically, make me lose about a pound per week, or 1800-500 + ride fuel.
I’ve read to take 15 times weight for moderately active women, and even more for very active. For myself, I could see taking 15, but not the next level, which might be 18 times weight. I'd gain eating that much, and probably the 15, too. Point is, know how many calories you need to maintain, and subtract 500 to lose in a healthful manner. (One that isn't too fast and forces your body to lose muscle rather than fat).
Most formulas and doctors' recommendations tend to exaggerate the amount of calories needed, and the amount burned. Same with formulas in Aps like MyFitnessPal.
Certainly, if you have been at your current weight for awhile, the place to start is to figure out your average caloric intake per day, maybe over the course of a couple of weeks, and go from there. But it does sound like you are under-fueling on the bike.
On the ride you mention, you ate approximately 1050 calories. If you look at online cycling calculators, they will probably tell you that is about the amount you burned per hour. I think that is exaggerated, but what you ate is still not nearly enough. You probably needed at least double. Depending.