Yes.
Research by Pleasant et al. found that horses that were overweight had higher insulin and leptin levels than horses that were the correct weight. Obese horses had higher triglyceride levels. They concluded that keeping horses at a Body Condition Score less than 7 might be important for decreasing the risk of pasture-associated laminitis.
Pleasant RS, Suagee JK, Thatcher CD, Elvinger F, Geor RJ
Adiposity, plasma insulin, leptin, lipids, and oxidative stress in mature light breed horses
J Vet Intern Med. 2013 May-Jun;27(3):576-82
Research by Pleasant et al. found that horses that were overweight had higher insulin and leptin levels than horses that were the correct weight. Obese horses had higher triglyceride levels. They concluded that keeping horses at a Body Condition Score less than 7 might be important for decreasing the risk of pasture-associated laminitis.
Pleasant RS, Suagee JK, Thatcher CD, Elvinger F, Geor RJ
Adiposity, plasma insulin, leptin, lipids, and oxidative stress in mature light breed horses
J Vet Intern Med. 2013 May-Jun;27(3):576-82