The Overweight Horse Who Won't Stop Eating - Leptin Resistance is the Key!
By Juliet M. Getty, Ph.D.
Your horse is overweight. You’ve been told to feed him a lot less hay and you’re desperately trying to do the right thing. But it won’t work! It won’t work for your horse any more than a strict diet would work for people. We have known this for years when it comes to human obesity. The reason is simple – dieting restricts calories, which lowers the metabolic rate. Weight loss may occur at first, but the body goes into “survival mode” and starts to hold on to fat and becomes sluggish in burning calories, making it extremely easy to put all the weight back on.
Horses have an additional issue: Their digestive tract cannot tolerate periods of time without food; it requires a steady flow of forage. There are several reasons for this, including the constant secretion of stomach acid, the potential for ulcers, the need for the cecum to be full in order for digested feed to exit at the top, and more. Please take a look at my book, Equine Digestion - It’s Decidedly Different, for a complete understanding of how the horse is designed on the inside.
Free-choice forage (hay and/or pasture) does not make a horse obese; on the contrary, restricting forage is what leads to obesity. You should reduce or even eliminate the amount of concentrates you feed (e.g., beet pulp, grains, commercial feeds, etc.) but you must never reduce forage (be sure to add a vitamin/mineral supplement to a hay diet). Ideally, you should test your hay[i] to make certain it is low enough in calories, sugar, and starch to be fed to an overweight horse (who is likely insulin resistant) and then, feed it free-choice, 24/7, all day and all night. At first the horse will overeat, but once he gets the message that the hay is always there, that he can walk away from it and it will still be there when he returns – then, and only then, will he start to self-regulate and eat only what his body needs to maintain condition. If you let him run out of hay, even for 10 minutes, he will always perceive that as a shortage, and will continue to overeat.
But why does self-regulation take forever to occur in some horses?
It often has to do with the way he was previously fed. If the horse had been enduring periods of time where there was no hay, his body went into starvation mode; that is, his metabolic rate severely declined. Now that you’re feeding free-choice, he will gain weight (which is temporary for most horses, especially if you are providing him opportunities to move). But for some horses, the drive to continually eat seems to never end and self-regulation appears impossible. The reason? Leptin.
Leptin comes from body fat
Excess body fat, especially regional fat deposits along particular areas of the body[ii], is a clear indication of the tissues’ reluctance to recognize insulin. Insulin is required for glucose (blood sugar) to enter the cells. When the fat slows down the tissues’ recognition of insulin, the pancreas will continue to produce more and more in an attempt to finally get glucose to enter the cells. Elevated insulin tells the tissues to hold onto body fat, making the horse even fatter.
Enter leptin. Leptin is a hormone that is secreted from body fat. It is a good hormone; it tells the brain that the horse is full and he can stop eating. This mechanism works perfectly for the horse of normal weight. But the overly fat horse does not get the message that he is satisfied; the signal that the brain is supposed to get that says I’m no longer hungry doesn’t happen. He has become leptin resistant.
In an effort to help the horse lose weight, more times than not the horse owner will be advised to severely restrict the amount that the horse eats, and this starts a vicious cycle: The horse will likely lose some body fat and hence, the leptin level will drop. A decline in leptin signals the horse to eat more, potentially gaining back all of the body fat lost (which also happens in humans[iii]) combined with a decreased metabolic rate making it very easy to put back the pounds. Forage restriction, in particular, is extremely detrimental because the stress involved will increase cortisol, which subsequently induces elevated insulin, which promotes fat storage, and you’re back where you started.
But that’s the key! The more body fat, the more leptin is produced. That should be a good thing, no? The higher leptin level should tell the brain that it has had enough to eat, right? That’s what leptin is supposed to do. But it doesn’t.
It has to do with inflammation. Body fat produces inflammatory molecules known as cytokines. These substances have two negative impacts: First, cytokines disrupt insulin action, reducing the cells’ insulin sensitivity, making your horse store more body fat. And second, and very important, cytokines impair the neurons in the brain’s hypothalamus[iv] —the area that normally responds to leptin!
What’s the solution?
Reduce inflammation.[v] This can be accomplished through dietary changes and adding anti-inflammatory nutraceuticals to the diet:
- Improve protein quality by feeding several sources: Mixed grasses and legumes, as well as whole foods such as ground flaxseeds, split peas, copra meal, whey protein isolate, hemp seeds, and chia seeds.
- Avoid added sugar and starch by eliminating sweetened feeds, cereal grains, wheat middlings, and rice bran.
- Avoid high-omega 6 oils, which are highly inflammatory (e.g., soybean, vegetable, corn, wheat germ, and safflower oils).
- Increase omega 3s by feeding ground flaxseeds and/or chia seeds. Fish oils can be included for high levels of inflammation.
- Look for a vitamin/mineral supplement that provides high amounts of antioxidants, particularly vitamins E, C, beta carotene (or vitamin A), and lipoic acid.
- Offer anti-inflammatory herbs such as yucca, grape seed extract, green tea extract, spirulina, curcumin, and boswellia.[vi]
By reducing inflammation, the brain will likely become more responsive to leptin, allowing the horse to stop eating when he is full. Stress needs to be eliminated through unlimited grazing on an appropriate forage. Slow-feeders can be useful in reducing intake.[vii] Combine all this with increased movement, and you have a formula for success.
[i] Testing your hay for its caloric content (digestible energy), as well as its sugar (ESC) and starch levels, is the only true way to know if the hay is appropriate to feed free-choice. Equi-Analytical Labs offers economical tests to provide equine-based results – https://equi-analytical.com. Equi-Tech test is recommended.
[ii] Areas include a cresty neck, crease going down the spine, fat along the ribs, behind the shoulders, on the tail head, and even over the eyes.
[iii] Rosenbaum, M., Goldsmith, R., Bloomfield, D., et al., 2005. Low-dose leptin reverses skeletal muscle, autonomic, neuroendocrine adaptations to maintenance of reduced weight. J. Clin Invest, 115, 3579-3586.
[iv] Guyenet, S.J., and Schwartz, M.W., 2012. Regulation of food intake, energy balance, and body fat mass: Implications for the pathogenesis and treatment of obesity. J. Clin. Endocrinol Metab., 97(3), 745-755
[v] Thaler, J.P., Yi, C., Schur, E.A., et al., 2011. Obesity is association with hypothalamic injury in rodents and humans. J. Clin Invest, 10.1172/JC159660.[PubMed]
[vii] Getty, J.M., 2014. "The Correct Way to Use Slow Feeders."
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