Effect of increased adiposity on insulin sensitivity and adipokine concentrations in horses and ponies fed a high fat diet, with or without a once daily high glycaemic meal.
Authors: Bamford N J, Potter S J, Harris P A, Bailey S R
Journal: Equine veterinary journal
Summary
# Editorial Summary Obesity in horses is frequently associated with insulin dysregulation, but whether excess body fat itself drives this problem or whether dietary composition plays the crucial role remained unclear until this 2016 investigation. Bamford and colleagues fed 18 horses and ponies either a high-fat low-glycaemic diet, an isocaloric diet with a daily glucose bolus (1.5 g/kg bodyweight), or a control ration over 20 weeks, measuring insulin sensitivity via frequently sampled intravenous glucose tolerance testing alongside adiposity markers and inflammatory adipokines. Both obesity-inducing groups achieved body condition scores ≥7 with substantially elevated total body fat mass and leptin concentrations, yet counterintuitively, the glucose-supplemented group demonstrated superior insulin-dependent and insulin-independent glucose disposal compared to the high-fat group and controls—suggesting that increased adiposity alone may not directly impair insulin sensitivity as previously assumed. Notably, adiponectin, TNF-α and serum amyloid A concentrations showed no differences between groups, indicating the inflammatory adipokine response was not the mechanism driving any insulin changes. These findings challenge conventional assumptions about obesity-driven insulin resistance in equids and indicate that dietary glycaemic patterns warrant more careful investigation as potential modulators of glucose metabolism independently of body fat accumulation.
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Practical Takeaways
- •Obesity itself may not be the primary driver of insulin resistance in horses—other dietary or management factors warrant investigation before assuming overweight horses are inevitably insulin-dysregulated
- •High-fat diets did not confer metabolic protection against obesity-related insulin changes, challenging assumptions that low-glycaemic feeding prevents insulin problems in obese individuals
- •Once-daily glucose feeding unexpectedly improved insulin sensitivity markers; feeding patterns and meal frequency may be more important metabolic factors than previously recognized
Key Findings
- •Increased adiposity alone did not reduce insulin sensitivity in horses and ponies fed either high-fat or control diets over 20 weeks
- •Once-daily high glycaemic glucose meal unexpectedly increased insulin-dependent (SI) and insulin-independent (Sg) glucose disposal compared to high-fat and control groups (P=0.006 and P=0.03 respectively)
- •Leptin concentrations were elevated in obese groups (FAT and GLU) compared to controls (P=0.003), but adiponectin, TNF-α and SAA showed no significant differences between groups
- •Body condition score and total body fat mass increased similarly in both FAT and GLU groups, suggesting dietary macronutrient composition rather than caloric load drives metabolic differences