Numerous sources of biological variation arise in rodents before translating results to humans is even considered. For instance, the age at which mice begin the high-fat diet greatly impacts the metabolic effects. In the strain of mice most commonly used for DIO models, C57BL/6J, mice who started the diet at 10 weeks old showed lower increases in body weight and cholesterol than mice who started at 54 weeks, despite the same diet type and duration. Similarly, 6-week-old mice did not develop type diabetes, while 7-8-month old mice did become diabetic due to differences in β-cell activity.
