Q: My horse has equine metabolic syndrome (EMS) but maintains a normal body condition score. Can horses have metabolic problems without being overweight?

A:  Yes! Horses with healthy body conditions can have metabolic issues such as EMS, just as some overweight horses can remain healthy. However, overweight horses more commonly have metabolic problems. A large body of evidence shows that adipose (fat) tissue can produce hormones and other chemical signals (known as adipocytokines) that can affect insulin signaling, resulting in insulin resistance and hyperinsulinemia, referred to as insulin dysregulation (ID). Even pockets of fat along the neck or tailhead area that might be present on a leaner horse could be problematic. Of course, horses with more adipose tissue produce more adipocytokines and are more likely to have ID. However, ID and EMS can also be influenced by the diet, particularly those high in starch and sugar (nonstructural carbohydrates or NSCs), or the horse’s genetics.

Why Monitoring Your Horse’s Insulin Matters

Regardless of the cause of EMS or your horse’s body condition score, work closely with your veterinarian to monitor your horse’s insulin concentrations because hyperinsulinemia-associated laminitis (HAL) accounts for up to 90% of laminitis cases. (Laminitis is a painful condition involving inflammation and damage to the tissues that suspend the coffin bone within the hoof.) Regularly checking your horse’s insulin concentrations can help determine how high that risk is.

Testing Horses for Insulin Dysregulation

Basal blood samples, taken at rest, ideally after a horse has only had hay for the previous six hours, are a common screening tool. However, your veterinarian might also suggest a dynamic test, such as an oral sugar test, to see how high your horse’s insulin levels get after a dose of glucose. It can also be particularly helpful to test the blood about 60-90 minutes after feeding your horse’s regular meal, or in the late afternoon if on pasture (because grass this time of day typically has the highest sugar content). This shows postprandial (after eating) insulin concentrations and would represent your horse’s real world risk for HAL.

Diet and Exercise for EMS Horses

Managing horses with EMS typically involves addressing diet and exercise. Reducing your horse’s calorie intake to facilitate weight loss (if overweight) and limiting NSC content to less than 10% of the total diet is important. This might require limiting or avoiding pasture access. Exercise—even low-intensity exercise such as walking, pole work, and hills—can contribute to better glucose metabolism (though exercise is not recommended in the acutely laminitic horse). If these methods do not fully control your horse’s insulin concentrations, your veterinarian might turn to medications to support diet and exercise changes.

Take-Home Message

Though rare, horses with normal body condition scores might develop EMS, and insulin monitoring is an important part of EMS management and laminitis prevention. Staying proactive with routine testing for your metabolic horse and working closely with your veterinarian can help you catch problems early and manage them more effectively.