Fixed rate home loans are not a particularly profitable category for lenders, even as demand for fixed rate loans has been rising.Mike Tilley, managing director of Challenger Financial Services Group said yesterday (at the bank's profit briefing for analysts) that "fixed rate (lending) is a product category that we don't think anybody is making any money out of."The proportion of fixed rate mortgage lending in Australia has doubled, to almost 20 per cent, according to data cited by Challenger yesterday.In response to this trend, ANZ yesterday said it would introduce a monthly loan administration fee of $10 on new fixed rate loans. The fee will not apply to existing loans. ANZ says other large banks already charge such a fee, while some other lenders do as well. Monthly administration fees are reasonably common on variable rate home loans with plenty of features as well and have been for years.