Insulin Resistance in Horses - Signs, Symptoms and Solutions

Insulin Resistance in Horses - Signs, Symptoms and Solutions

Posted by Marijke van de Water on 2018 Jul 23rd

So many of our horses are struggling with weight gain, easy-keeping, and lack of exercise, all of which results in Insulin Resistance (IR). IR causes a variety of different symptoms and is mostly caused by the over-feeding of sugars and starches, usually combined with a lack of exercise or stress.

Easy Keepers at Risk

It often affects the at-risk ‘easy keeping’ breeds: ponies, Minnies, Icelandics, Arabs, Mustangs, Morgans, draft horses and gaited horses. Although to be honest, almost all breeds are now susceptible because of the domestic environment that we have forced them into.

Easy keepers are ‘easy’ because their ancestry and metabolism is adapted for survival in harsh, low nutrient environments rather than lush sugar-laden pastures with oats for dessert. The over-weight horse standing knee-deep in a lush grass field with no reason to walk or run, other than to graze and saunter over to the water trough is a classic image. However, IR is now also seen in recreational horses and even performance horses.

Senior horses are also prone to IR which is to be expected since their overall metabolic rate is lower, their stress coping abilities are reduced, and their hormones are no longer as efficient.

How It All Begins

IR occurs as a result of over-feeding unsuitable feeds and unrestricted grass grazing usually combined with lack of exercise. When blood sugar rises after eating, insulin is secreted by the pancreas to open up glucose receptors in the muscles and liver. This transports the sugars out of the blood and into the tissues for energy or for storage.

Normally sugars are stored in the muscles and liver as glycogen – the storage form of sugar – from where they are converted back into sugar and released into the blood when needed for energy. However, when the muscles and liver storage depots are full the receptors will no longer respond to insulin and will therefore not open to allow the sugars entry into the tissues. At this point the insulin production will continue to rise in an effort to keep signaling the receptors to open.

Sugars which cannot be stored as glycogen must now convert to fat or triglycerides resulting, of course, in weight gain and sometimes a fatty liver. Blood sugar and insulin imbalances can also disrupt other endocrine glands including the adrenals, thyroid and pituitary as they work harder to regulate the insulin levels and the disruption to the metabolism.

Once the fat cells are full the sugar, with nowhere else to go, will continue to rise in the blood resulting in a condition known as diabetes. High blood sugar levels are responsible for a number of different problems including poor immunity, fatigue, thirst, increased urination, general inflammation, body soreness, and perhaps most significantly, laminitis, as the circulation sugar adversely affects the tissues in the hooves. This is a particular problem if the hooves have not been properly trimmed.

The Dangers of Cortisol

When insulin levels are consistently high, the cortisol levels produced by the adrenal glands will rise as well. Cortisol is the stress hormone produced by the adrenals that plays a significant role in immunity, inflammation, stress, carbohydrate metabolism, mental well-being, hoof health and weight gain. Cortisol is catabolic meaning that it degenerates tissue, including hoof tissue. And, once insulin and cortisol levels rise they interfere with both the thyroid and pituitary hormone production.

Low thyroid slows down the metabolism causing further weight gain, poor immunity, poor hoof circulation, digestive problems, fatigue, and mental irritability or depression.

If high cortisol levels continue then the pituitary, a small gland at the base of the brain, is signaled to help regulate the unbalanced adrenal function by producing adrenocorticotropic (ACTH) hormone. If the underlying problems of blood sugar, insulin production and/or adrenal function are not corrected then the pituitary becomes hyperactive which then affects the balance of all the other hormones including the thyroid. This pituitary condition known as PPID or Cushing’s disease is evident by the presence of curly hair, poor shedding, sweating, low energy or depression. Pituitary dysfunction can also cause imbalances with estrogen, progesterone, and testosterone; hormones that are also important for healthy metabolism, energy levels, immunity, and overall well-being including emotional health.

The Role of Leptins

Leptin, a hormone released from fat cells, sends signals to the hypothalamus in the brain to tell the brain that the body is full of food. It is therefore called the satiety hormone because it inhibits hunger and regulates energy levels by only triggering hunger when it needs energy. Therefore, the primary purpose of leptin is to help the body maintain normal weight; it is the master hormone of body fat regulation.

When levels of this hormone fall, it sends a ‘starvation alarm’ to the brain triggering huge increases in appetite and food cravings – usually sugar, as well as an increase in fat storage. It also reduces the motivation to exercise and decreases the resting metabolism which slows weight loss.

And while overweight horses may have enough leptin, many of them have become “leptin resistant” (LR); like insulin resistance the body becomes resistant to any hormones which are excessively high. This is part of a defense mechanism to protect the body’s metabolism. Once a horse is leptin resistant the fat cells nor the brain are receiving the leptin signal to burn fat or to stop eating. This causes the brain to think that it needs to conserve energy because it is missing fat, so the horse becomes lazy and heavier.

6 Ways to Help Your Horse Overcome Insulin Resistance

1. EXERCISE is critical in helping your horse overcome weight gain, LR and IR. Horses should be encouraged to exercise two-three times per week through hand-walking or jogging, light riding, ponying, liberty work, or playing with other horses. Studies show that within three weeks of regular exercise the insulin receptors quadruple. In addition, regular exercise increases the metabolism, accelerates weight loss, improves the immune system, contributes to mental well-being, and is critical to maintain healthy hooves.

2. USE SLOW FEEDERS so that they do not run out of hay at any given time. Slow feeders help stabilize blood sugar, reduce stress levels, improve digestion and promote weight loss. Many times people want to restrict an IR horse from eating by reducing their feeding times and their quantities of hay. However, anytime that a horse gets hungry and cannot graze, forage or nibble, their stress levels rise and so do their stress hormones. Stress causes the adrenal glands to produce higher cortisol levels which then increases weight gain, depresses the immune system, and disturbs the metabolic hormones including insulin and leptin. When leptin levels drop due to lack of food, it triggers extreme hunger. Restricted feeding also adversely affects digestion resulting in more cases of acidity and/or colic.

Click here more information on slow feeders:

3. REDUCE STRESS. Stress will exacerbate Insulin Resistance and interfere with hormone production including reproductive, adrenal, thyroid, and pituitary hormones. Stress also causes inflammation, pain, and soreness.


  1. Eliminate all high sugar feeds including grains, oats, corn, and barley
  2. Eliminate or drastically reduce grass grazing
  3. Eliminate all commercial feeds which often contain cheap by-products and ingredients that drive inflammation
  4. Feed a low-sugar hay in slow feeders
  5. Increase fibre with two cups of soaked beet pulp if tolerated and add extra protein such as one cup of alfalfa pellets, also only if tolerated. Fibre and protein help to decrease the absorption of sugars from the intestines into the blood.

5. AVOID THE USE OF NUTRACEUTICALS. Horses who are overweight, have IR or any other metabolic issues should avoid using nutraceuticals such as glucosamine or chondroitin. These products are concentrated sugars and are therefore contraindicated in metabolic problems. They interfere with insulin production, can increase blood sugar levels, promote weight gain, and cause heart irregularities.

Note: Use extreme caution feeding alfalfa to laminitic horses, arthritic horses, or horses prone to colic.



Pro-Colon – ¼ tsp daily
Pre- and probiotics, improves digestion and nutrient absorption, aids intestinal immunity, aids leaky gut

Blood Sugar Formula

Blood Sugar Formula, homeopathic – One dose (5-10 sprays) daily for 21 days.
Encourages weight loss, promotes normal blood sugar levels and insulin production. Regulates appetite.

Vitamin B6

Vitamin B6 – 1 tsp daily (= 750 mg)
Blood sugar regulation, insulin production, immunity, hormone nutrient, weight loss. Thyroid and pituitary nutrient.

Vitamin B12

Vitamin B12 - 1 tsp daily (= 6,000 mcg)
Colon support, improves metabolism, liver detoxification, nerve nutrient.