Riding, or at least riding well, is a high-skills, fast-paced, high-risk sport, up there with downhill skiing, white water kayaking, etc. For those sports, no one questions that you need to be in good fitness, and participants self-select for athletic ability.
Many excellent riders (pros, coaches, trainers) have the ability, inclination, and fitness to participate in these other high-skill, high-risk, sports. But riding at the lower levels attracts a large number of people who are not athletic at all, not fit at all, who do no other high-skill, high-speed, sports, and wouldn’t dream of even trying one. They are attracted to riding because they love horses, and because at the lower, beginner, end of riding, being a passenger on a horse can compensate for not having much physical strength or skill on the ground, or in the saddle. Riding a horse can be very empowering, in this way.
The problem, though, is that this means you get far more unfit, unathletic, people wanting to be riders, than you would get wanting to downhill ski, scuba dive, race sail boats, rock climb, etc.
Weight in the United States is very directly linked to economic status, class, race, and region of the country. I would expect that in an expensive hunter/jumper barn on one of the coasts, you are going to see a lot slim young women, the kind who are slim enough already but then are susceptible to fad diets and eating disorders on top of that. This is the kind of environment where girls can get shamed about having any body fat whatsoever, and where the prevailing competitive atmosphere would encourage everyone to go for any advantage whatsoever, whether it is good or bad for their health (or for their horse).
In this environment, as an instructor, you might get students who were “thick,” and never going to look as willowy on a horse as the 5 foot 10 115 pound child. You might get a few adults or returning riders who were 20 or 30 pounds overweight. But you probably would never see a truly obese person from one year to the next. And, interestingly, this is the kind of environment where large horses are currently valued, the kind of place where re-riders want the 17 hand dream warmblood now.
In other parts of the country, almost everyone right up to the upper middle classes is over weight, and the prevalence of actual obesity is much higher too. There is less of a culture of physical fitness, fewer places to work out, and in some cases a climate that makes outdoor activity unpleasant. There is less general information about diet and nutrition, even among people who are otherwise well informed. And there can be fewer options for healthy eating, as well as cultural pressures to eat and enjoy high calorie foods.
I can totally imagine that if you were running a beginner riding program in this kind of area, that you would see many clients who were 20 to 30 pounds overweight, and a significant number that were clinically obese, to the extent that it interfered with their position and balance in the saddle. And if you were in a discipline or area that favored small horses (arabs, QH), that would make the problem worse.
I’ve lived in both types of places in the US, not in horses but in academia, and saw the clear differences in body type in my colleagues and in my students, and how it correlated to life-long patterns of eating and exercise, as well as to the prevalent norm. Sometimes I think the only options are anorexia or obesity, that there is very little room for a middle ground of sturdy and healthy, at least for women.
So, depending on where the OP is located, and what the average body type of the average young woman in her area is, she might in fact be seeing far more genuinely overweight or obese students than anyone in a high-end East Coast barn could ever imagine.
