1. He rolls in the dust and can't get back up
2. Endurance riders ask if they can ride laps around him
3. Your farrier arrives with a back brace and an engine hoist
4. Friends ask, "when did you get the pregnant mare?"
5. Meat buyers stop by your farm "just to chat"
6. He tries to nip your foot while riding, but can't bend that far
7. When trotting, he leaves hoof impressions in hard pavement
8. You have to grease the stall door to lead him out
9. On a hot day, other horses rest in his shade
10. Your girth is actually two girths and tie-down winch strap
11. You can't longe him because he leaves ruts in the round pen
12. He gets in the trailer, and the truck tips upwards
13. You start to become bow-legged after two rides
14. Your neighbor says an escaped hippo is in your pasture
15. Your vet wants to try the world's first equine liposuction
16. You can't canter, because people complain about the thundering noise
17. He becomes breathless after looking at a hot walker
18. Rather than attempt to pass you on trails, people just turn around
19. While riding, you start to pay attention to weight capacity signs on bridges
All hilarity aside, obesity in horses is even more dangerous than obesity in humans. Be sure to check for fat pockets, excess sweating and heavy breathing while working, and other signs of obesity. One of the easiest ways to tell if a horse is overweight is by standing behind him and looking at this backbone. It should be a slight hill, not a shallow valley:
Unfortunately, this isn't a fool-proof test. A horse can still have a normal looking backbone and still be overweight, especially if he has metabolic issues-- the fat tends to collect in different places. You also shouldn't trust a weight tape-- they're not very accurate, especially for longer-bodied horses and horses with big butts/necks. A measurement taken in one place does NOT give you the whole picture. Here's one example of that, in human form:
How did she even fit in....? You know what, I don't wanna know. LOL, People of Walmart is a funny site, but I'm not linking to it because it has so many viruses and ads. Go get the book instead :) Here's a nice diagram (not made by me) about where fat deposits tend to collect on a horse:
...now get out there, and give your buddy some exercise!