Metabolic and Hormonal Response to a Feed‐challenge Test in Lean and Overweight Dogs

Background Obese dogs risk poor life quality, creating a need for increased knowledge of metabolism in overweight dogs. Objectives Investigate postprandial metabolic and hormonal responses to a high‐fat mixed‐meal in dogs and responses of lean versus overweight dogs. Animals Twenty‐eight healthy intact male Labrador Retrievers were included. Methods Prospective observational study. Twelve dogs were grouped as lean (body condition score (BCS 4–5), 10 as slightly overweight (BCS 6), and 6 as overweight (BCS 6.5–8) on a 9‐point scale. After an overnight fast, urine and blood samples were collected. Dogs were then fed a high‐fat mixed‐meal, and blood was collected hourly for 4 hours and urine after 3 hours. Results Postprandial concentrations of insulin and glucagon were increased at 1 hour (both P < 0.0001), triglycerides at 2 hours (P < 0.0001), and glucose at 3 hours (P = 0.004); and all remained increased throughout the feed‐challenge in all dogs. Postprandial urine cortisol/creatinine ratio was higher than fasting values (P = 0.001). Comparing between groups, there was an overall higher triglyceride response in overweight compared to lean (P = 0.001) and slightly overweight (P = 0.015) dogs. Overweight dogs also had higher fasting cortisol/creatinine ratio compared to lean dogs (P = 0.024). Conclusions and Clinical Importance Postprandial responses of dogs to a high‐fat mixed‐meal were similar to those previously reported in people. The higher postprandial triglyceride response and fasting cortisol/creatinine ratio in the overweight dogs could be early signs of metabolic imbalance. Thus, although overweight dogs often appear healthy, metabolic alterations might be present.