I don't like to see any "points" - hips, sacrum, shoulder - on my horses, but I don't want them to be fat, either. My objective is for them to be lean, well-muscled and fit. I like to be able to feel the last rib or two as I run my hand along their barrel, and I'd like to see a suggestion of ribs when they're in motion. And I certainly don't want to see any accumulation of fat over the loins, a thickened crest on the neck, or tailhead fat, or fat on the belly in front of a mare's udder (what I call a "pooch").
Here's Maisie from a few years ago displaying tailhead fat - notice that bump in the smooth curve from the high point of the rump down to the tail:
and a "pooch":
Why do I care that my horses not get fat? Just as with people, when a horse is fat it puts extra stress on joints and soft tissues, making injury more likely, and being fat can predispose a horse to metabolic problems (particularly if the horse is genetically primed), including insulin resistance and foot problems such as laminitis.
So, what can I do to keep my horses at a healthy weight? First, reduce or eliminate concentrated feeds - most pleasure horses do not need much if any grain, and even a horse in heavy work will benefit from nutrient-dense but low NSC (non-structural carbohydrates that are easily digested) feeds, and some of these feeds are also high fat. My horses get a vitamin and mineral balancer pellet that is formulated for our area, and rice bran or beet pulp if needed in winter for weight maintenance. Quality forage is the foundation of a good diet for horses. Oils can be good, but they very widely in their omega 3/6 ratios.
Second, maximize movement. The more turnout the better, and regular work on the line and/or under saddle is desirable. I'm wrestling a bit with the turnout situation right now - due to the amount of grass we have - way more than our tiny herds need - 24/7 turnout was leading to undesirable weight gains, particularly for Dawn. (I don't like it when someone meeting my mare for the first time tends to ask: "When is the baby due?") My horses are generally stalled for part of a 24-hour period - right now this tends to be during the day due to the heat - and get a controlled portion of hay during this time.
Pie's looking good right now - he's only on the grass part-day and in a dry-lot paddock the rest of the time. Drift was starting to chub up, but now that he's on solo turnout he's on a sparse pasture for part day and in a small paddock with minimal grass the rest of the time, and I've been riding him regularly, so he's starting to look better. Dawn is frankly fat, although she doesn't have the dreaded tailhead fat or a crest (yet), so I've reduced her hours of grass turnout to control her intake. More riding would help her as well. All three get good-quality grass hay spread through the day so they're eating small meals continuously, which is how horses are designed to eat.
We're keeping an eye on the "battle of the bulge"!