Weight loss in horses can be a difficult struggle for owners.  Obesity is a welfare concern as excess adipose tissue can result in generalized inflammation, be a risk factor for equine metabolic syndrome and insulin dysregulation, osteoarthritis and reduced performance.  However, simple caloric restriction may not result in whole body changes in adiposity.

The use of body condition score is a common tool to assess the degree of adiposity of the horse and reflects the palpation of specific locations on the horse's body.   Best practices include providing a score to each "part" of the horse and then compiling an average. However, specific locations of adipose tissue are more correlated to disease risk.   Adipose tissue over the tailhead and nuchal crest have higher expression of pro-inflammatory adipokines and cytokines than do regions with more subcutaneous fat. Therefore, just as in humans, all fat is not equivalent.
Further, weight loss studies of feed restriction or feed restriction plus exercise have either found the two methods are equivalent or that the inclusion of exercise is more effective in achieving weight loss.  However, these studies have looked at changes in BCS in its entirety or weight loss in general. Therefore, it is unknown if diet alone, or diet plus exercise would result in greater changes in adipose tissue at specific locations in the horse that may yield better overall health outcomes.

Thirty-two horses with a BCS of at least 7 were enrolled in a weight loss of regimen of either a restriction to 85% of their energy requirements, 85% caloric restriction with an additional work load to utilize 15% of their caloric intake, and no restriction of calories but a similar degree of exercise. A control group was also included but should be noted that the horses went from free choice intake, to restriction of 100% of intake needed to maintain weight. Exercise was performed on a longe line at a trot for a total of 20 minutes 5 days per week.  Horses were weighed, an average body condition score was taken, as well as scores for 8 individual locations (neck, shoulder, inner front legs, withers, ribs, crease down back, crease down haunches and tailhead).

All groups decreased weight in the first 5 weeks (even controls fed at 100% of energy requirements), but horses in the exercised group continued to lose weight until week 10. While all groups reduced overall BCS, only addition of exercise was effective in reducing cresty neck and tail head scores.
It should be noted that the control horses were transitioned from free choice hay intake to only 2% of their body weight, which is certainly a reduction in caloric intake, as many horses will willingly consume more than 2% of their body weight.  Addition of exercise did not change the effects of simple feed restriction on body weight or overall BCS. However, feed restriction alone was unable to create reductions in adiposity in the neck and tailhead, which indicate an addition of exercise (if tolerated) is necessary or potentially a greater restriction in caloric intake. Therefore weight loss programs that can create reductions in cresty necks and tailheads may be more physiologically relevant.

Garland et al. BMC Veterinary Research          (2025) 21:596 https://doi.org/10.1186/s12917-025-05032-z

Article by OSU equine newsletter