Considerations to maximize fat mass gain in a mouse model of diet-induced weight gain.

Mouse experimental models of diet-induced weight gain are commonly used as analogs to human obesity; however, a wide variety of feeding methods have been used and the most effective way to maximize weight gain is not known. Maximizing weight gain may allow for a reduction in the number of animals required for a given experiment. The purpose of this study was how to cause the greatest amount of weight gain in CD-1 mice by modifying the composition and source of their diet. To accomplish this goal, we completed two experiments: (1) Effect of dietary macronutrient fat intake (60% (HF60), 45% (HF45), 30% (HF30), or 13.5% (CON) fat diet for 18 weeks); and (2) Effect of 1:1 mixed HF60 and CON diets. Outcome measures included food intake, body mass, and body composition, which were measured bi-weekly and statistically analyzed using a repeated measures analysis of variance (RM-ANOVA). In Experiment 1, the greatest increase in body and fat mass was observed in HF60 (36%) and HF45 (29%) compared with HF30 and CON (P < 0.05). In Experiment 2, HF + stock diet (SK) gained 25% more body mass and 70% more fat mass than HF (P < 0.05). Collectively, these findings suggest that using a high-fat based diet (>45% calories from fat), mixed with a stock diet, results in substantially more weight gain over a similar period, of time, which would allow an investigator to use ~40% fewer animals in their experimental model.