Published on March 11, 2025

There are two reasons for horses to become obese. The first reason is that they eat more calories daily than they use. The intake of calories is in the form of excess starch from hay and grains and excess fat from the digestion of cellulose in the hindgut.

The second reason is often misunderstood. There must be a demand for the fat stored in the body fat; otherwise, it will remain or even increase body fat. The demand is created when muscle cells are used to the point of exhaustion, which, in terms of metabolism, means the lactate and glycogen are nearly all consumed within the muscle cells. This exhaustion of glucose and lactate forces the cell to use the fat stored within the cell, thus creating a demand for replacement of cell fat from body fat stores.

Horses with limited exercise ability (lameness, age) should still be encouraged to move, but they will need less food. However, remember that calorie restriction signals the horse to maintain or increase body fat because it will believe there is little food available, so it needs to conserve energy. Increasing exercise allows for adequate calorie consumption due to its effect of lowering hunger.

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