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.