Increased calorie needs when shedding?

My old horse, a hard keeper, was a ball-ache to keep weight on during the winter. But some winters I’d feel like I won a million bucks because she would get to February and still look great. Then inevitably, March came along, and she’d drop tons of weight. It always seemed to coincide with her blowing her winter coat, but I never knew if it was actually a thing or a coincidence.

Too bad that theory doesn’t seem to be working for my two easy keepers. Now that would be useful.

My understanding is that hormones change in fall so they put on more fat to get ready for the cold, and then in the spring they change again to get ready for the rich grass of spring time, so they adapt for the calorie changes that would occur in nature (but don’t occur in a horse keeping situation)