Lean horses can still have EMS, new sport horse data suggest
Bottom line
Horses can have equine metabolic syndrome, or at least its hallmark feature, insulin dysregulation, without looking overweight. That’s the key takeaway from recent coverage and supporting research on sport horses, including a North Carolina State University study reported October 23, 2026, by The Horse. In that cohort of 180 sport horses, 41 horses, or 22.8%, tested positive for insulin dysregulation on an oral sugar test, and body condition score and neck fat were not associated with which horses were affected. The same report found fasting insulin alone missed most positive cases: only 11 of the 41 insulin-dysregulated horses were identified on fasting insulin, while the oral sugar test picked up the remaining 30. Broader veterinary guidance also makes clear that lack of obesity does not rule out insulin dysregulation or EMS. (thehorse.com)
Why it matters: For veterinary professionals, the message is practical: visual assessment is not enough. Current references emphasize that EMS diagnosis should focus on documenting insulin dysregulation, not just body condition or a cresty neck, because some horses have normal weight yet still carry meaningful laminitis risk. That makes dynamic testing, especially the oral sugar test, more important when evaluating at-risk horses, including athletic animals that might otherwise be missed in routine screening. (msdvetmanual.com)
What to watch: Expect more discussion around when to add dynamic insulin testing to routine sport horse and pre-laminitis workups, especially as stall-side screening options continue to be evaluated. (thehorse.com)
Key facts
- Study
- North Carolina State University sport horse study
- Reported
- October 23, 2026
- Sample size
- 180 sport horses
- Positive cases
- 41 horses, or 22.8%, tested positive for insulin dysregulation
- Main finding
- Body condition score and neck fat were not associated with insulin dysregulation
- Testing result
- Fasting insulin identified 11 of 41 affected horses; oral sugar test found the remaining 30
- Clinical takeaway
- Horses can have insulin dysregulation without being overweight
A horse doesn’t have to be overweight to have equine metabolic syndrome. Recent reporting in The Horse and EquiManagement highlights a point many equine clinicians already suspect: insulin dysregulation, the core metabolic abnormality linked to EMS and hyperinsulinemia-associated laminitis, can be present in fit-looking, actively working horses that don’t show classic obesity or a pronounced cresty neck. In a North Carolina State University sport horse study covered October 23, 2026, nearly 1 in 4 horses tested positive for insulin dysregulation despite physical appearance being a poor predictor. (thehorse.com)
That finding fits with the broader evolution of EMS thinking. More recent reviews and consensus guidance define EMS less as a simple obesity syndrome and more as a cluster of metabolic and clinical features centered on insulin dysregulation and laminitis risk. Obesity is common, but it is not required for diagnosis, and absence of obesity does not exclude disease. The MSD Veterinary Manual states this directly, and the 2019 ECEIM consensus statement likewise frames diagnosis as a combination of history, clinical examination, and laboratory testing, with insulin dysregulation as the most important risk factor. (msdvetmanual.com)
The new sport horse data sharpen that point for everyday practice. According to The Horse, NCSU investigators evaluated 180 sport horses from the university hospital and local farms using an oral sugar test and diagnosed insulin dysregulation in 41 horses, a prevalence of 22.8%. Just as important, body condition and neck fat were not associated with insulin dysregulation in that population. That matters because sport horses can look lean, muscular, and clinically well while still carrying endocrine risk that could influence laminitis prevention, feeding plans, and even medication decisions. (thehorse.com)
The diagnostic implications may be the most actionable part of the story. In the NCSU report, fasting insulin alone identified only 11 of the 41 affected horses, meaning most positive cases would have been missed without dynamic testing. That aligns with AAEP proceedings and other published work showing basal insulin is an insensitive standalone screen and that low fasting insulin does not rule out insulin dysregulation. The MSD Veterinary Manual similarly recommends moving to an oral sugar test or oral glucose test when baseline insulin is normal but suspicion remains. (thehorse.com)
This also isn’t the first sign that non-obese horses can be affected. A 2024 study in non-obese stock-type horses, indexed in PubMed, specifically reported that insulin dysregulation may present without obesity. Earlier literature has also shown that morphometric markers such as neck measurements are imperfect proxies for metabolic status. Taken together, the evidence suggests clinicians should be cautious about relying on phenotype alone, particularly in breeds or use types where excess adiposity may be less obvious. (pubmed.ncbi.nlm.nih.gov)
Expert and industry commentary has been fairly consistent. In The Horse report, Lauren Schnabel and Kimberly Hallowell emphasized that testing is the only way to confirm which horses are affected, and Schnabel said dynamic testing can help clinicians catch cases earlier and reduce laminitis risk. The same coverage noted a potential downstream management issue for sport horses: these patients commonly receive intra-articular corticosteroids, and the researchers flagged prior findings suggesting steroid joint injections can worsen insulin dysregulation, which could alter risk-benefit discussions in susceptible horses. (thehorse.com)
Why it matters: For veterinary professionals, this is a screening and case-management story as much as a research story. If EMS is still being mentally filtered through an “overweight horse” template, some cases may be missed until laminitic change is already underway. Current guidance recommends focusing diagnosis on insulin dysregulation, taking a careful diet and laminitis history, and examining the feet even when no laminitis has been recognized by the pet parent. In practice, that may mean a lower threshold for oral sugar testing in horses with unexplained laminitic history, regional adiposity, breed predisposition, performance-horse medication exposure, or recurrent metabolic concerns despite normal body condition. (msdvetmanual.com)
What to watch: The next step is whether these findings change field screening habits. Clinicians will likely watch for publication of the underlying sport horse study, wider uptake of dynamic testing protocols, and more validation work on rapid stall-side insulin assays that could make screening easier in ambulatory practice. (thehorse.com)