In the rugged cowboy country of western Colorado, master saddle maker Bob Klenda has noticed a troublesome trend since he started stitching leather in 1961: The typical horseback rider has a much bigger posterior. So Klenda's custom saddles are bigger than ever.

Klenda tells ABC News: "When I started 50 years ago, 14 inch saddles were common and a 15 inch (saddle) was considered a big seat." Now, Klenda says, 15 ½ to 16 inch saddles are standard. (On Western saddles, the measurement is from front to back-the pommel to the top of the seat.)The custom saddle producer now even makes one or two 17-inch saddles among the dozen he turns out each year.

"Those were unheard of back in the 60's and '70's," he says.

The super-sized saddles reflect the fleshy facts: Americans are fatter than ever. More than a third of us are obese, according to the Centers for Disease Control.

"The saddles are bigger and so are the butts," says Lucille Nieslanik, owner of Broken Heart Ranch in Haugan, Montana-a former dude ranch that now caters to hunters. "When I was growing up, people walked more and just did more physical activity," Nieslanik tells ABC News. She says the saddles and customers "have definitely gotten bigger" since the business opened in 1976. Now, she is careful to match up horses with customers so the animals are not strained.

But even the horses are getting bigger to accommodate fatter Americans. Saddle-maker Klenda says dude ranch operators in Colorado are breeding draft horses with smaller stock so the animals can safely bear the strain of ever-larger wannabe cowboys.

At the K-Diamond-K guest ranch, 125 miles north of Spokane, Wash., owner Kathy McKay tells ABC News they are breeding Clydesdales-made famous in those Budweiser commercials-with quarter-horses just to make sturdier animals for bigger customers. Otherwise, McKay says, overweight riders "really take a toll on those poor horses."

At the ranch, also a veterinary clinic, the vets find horses becoming arthritic at younger ages because of heavier riders. K-Diamond-K used to impose a 230-pound weight limit on riders, but McKay says it became difficult to enforce because so many customers weigh more than that.

Now, she says, "it's a judgment call" as to whether riders are turned away for being too heavy. "We try to be as tactful as possible."