Quick Answer: My horse is too fat? This is important and can lead to laminitis. You will need to restrict the amount of calories he is getting, restrict grass perhaps by using a grazing muzzle, make sure your hay is low in sugar and feed 1.5% of body weight. No extra hard feed only a balancer like Lite and Lean. If people are saying “wow he’s put on weight” you may need to consult a vet or horse nutritionist.
Learn the signs of a fat horse, fat feels softer than muscle so feel his crest, it should hardly be there. Run your hand over his ribs, can you feel them but not see them? Then learn the way to fat score your horse and do this every week, you can also use a weigh tape and record the weight to see them reduce. There is a free Laminitis Log Book to download on www.litebitehorsemuzzle.com you can record everything in there.
Exercise is important, even if it is only walking out, go with energy either walking or riding and/or lunging is good too.
Why bother with all this? Well an overweight horse is at risk of laminitis and from experience, I can tell you it is beyond awful. It is painful and means the horse will always have a higher risk of relapse – so take action before that happens.