Much like humans, horses need a proper diet and adequate exercise to maintain a healthy body weight.

Do you have a full-figured mare that practically plumps up just by looking at green pasture? Have you owned a beer-belly gelding that would rather snack and watch the equine version of Sunday football than get out for a bracing walk? You’re not alone.

Although the 1998 National Animal Health Monitoring System survey reported the prevalence of overweight or obese horses to be only 5%, a 2008 Virginia-Maryland Regional College of Veterinary Medicine study suggests that obesity might be grossly underreported: Researchers found 51% of the horses sampled had a body condition score (BCS) greater than 6, including 19% with scores of 8 to 9. Normal BCS is 4-6 out of 9. A subsequent study at North Carolina State University showed 20% of horses were obese. While the incidence wasn’t as high as in the Virginia study, equine obesity is still a problem.

As with humans, underexercising, overeating, and high-cal foods are the primary culprits for that ever-increasing girth. Genetics is another factor: Some breeds, breed types, and individuals retain or gain pounds on the same diet and exercise routine that keep their stablemates trim. For example, draft breed weanlings only need about 80% of the calories that Thoroughbreds or Standardbreds require.

Regardless, the recipe for keeping pounds off the plump-prone pony or for shedding excess weight is the same for horses as it is humans: Fewer calories, more exercise.

Since your hefty horse isn’t likely to voluntarily hit the gym anytime soon or turn his nose up at th