How Chronic Stress Alone Can Contribute to and Even Cause Insulin Resistance

August 3, 2026

Cortisol, Blood Glucose and High Insulin Explained

Hi, I'm Katey, Equine Holistic Nutrition Practitioner and Equine Osteopath. I talk everything crunchy and holistic horse care. If your horse seems grumpy, reactive, reluctant to work, is just not themselves, or has any of the typical signs I describe in my prior blog, and no one can give you a straight answer about why, the answer might be living inside their physiology. Today we are unpacking that in a way horse owners can actually understand.

Today we are talking about how chronic stress affects your horse’s internal chemistry, how that chemistry affects behaviour and comfort, and how you can start supporting your horse naturally through awareness, nutrition, environment, and management.

Cortisol is your horse’s primary stress hormone. It is meant to rise during short bursts of stress such as danger, movement, excitement, herd dynamics, or environmental changes. In those moments, cortisol tells the body to release glucose for quick energy. That is normal and healthy. The problem begins when stress stops being temporary and becomes a constant background noise in your horse’s life. When cortisol stays elevated, glucose stays elevated. And when glucose stays elevated, the body keeps producing insulin to deal with it. Over time, the cells stop responding properly to insulin’s signal. Now you have a horse living in a state of chronically high glucose and chronically high insulin, and that internal dysfunction shows up externally as behaviour changes, discomfort, inflammation, and eventually metabolic issues.

Here is the part I need you to hear: high insulin is not just a metabolic concern. It affects the entire body. It tightens blood flow in the hooves. It increases inflammation in soft tissues. It activates pain pathways, especially in the feet and lower limbs. A horse who refuses to move forward, pins their ears during grooming, flinches at the girth, or seems moody under saddle may not be misbehaving. They may be uncomfortable in ways no one has ever connected to their internal chemistry.

This is where the cycle becomes vicious. Chronic stress raises cortisol. Cortisol raises glucose. Glucose demands more insulin. High insulin creates inflammation and pain. Pain is a stressor. Stress raises cortisol. And the loop continues. This is why some horses slowly deteriorate even when nothing obvious has changed in their environment. Something has changed. Their internal systems have been struggling for months or years.

And here is something most horse owners never hear: chronic stress alone can cause insulin resistance. Stress is not inherently bad. Horses experience stress throughout their lives. The issue is when stress becomes constant and the body can no longer regulate it. Emotional stressors like isolation, travel, herd instability, food scarcity, or human pressure activate the same internal pathways as physical stressors like hoof pain, ulcers, saddle fit issues, or chronic discomfort. The body does not differentiate. Stress is stress.

The chain looks like this: Stress → cortisol → glucose → insulin → inflammation → more stress.

A stressed horse can look metabolic even when the diet is not the main problem. And once insulin is high, it creates inflammation and pain which creates more stress which keeps the cycle going. Add a high sugar diet, mineral imbalance, or gut dysfunction on top of that and you have the perfect storm.

So what can you do? Start by looking at the whole picture. What is your horse eating? Is the forage balanced? Are they on lush pasture? Are they receiving minerals that actually match their health profile or just a generic multi vitamin? Are the minerals they are getting being absorbed? Are they living in a way that supports their nervous system with consistent routines, herd companionship, movement, and safety? Are there physical stressors like hoof discomfort, saddle fit issues, or chronic tension patterns? All of these contribute to the cortisol load.

Holistic care starts with awareness. When you understand how your horse’s internal systems respond to stress, nutrition, and environment, you can start making changes that support healing instead of accidentally feeding the cycle.