Figure 1. Setup to measure water balance in mice of different ages.

A) Diagram showing experimental design. Mice were placed in metabolic cages and subjected to 4 consecutive periods (3 days each) of progressively reduced water content (from 56% to 33%) of their gel food. B) Consumption of food and water, calculated based on the water content of the gel food and the amount of gel food consumed each day (median and IQR, n = 3–4, ^# P<0.05 relative to 56% water in gel food). 3 and 18 month old mice eat similar amount of food at all water availability that does not change with decreasing water content. 27 month old mice decrease amount of food eaten when water content decreases to 33%.