IT could be the ultimate diet food - low fat chocolate which is 60 per cent water but tastes exactly like a normal bar. Researchers at the University of Birmingham say their breakthrough, in which they replaced the fat, could lead to new ways to deal with rising levels of obesity. The team is also developing mayonnaise with five per cent fat that tastes identical to the full-fat version, and porridge that stays in the stomach for five to six hours, stopping people feeling hungry. The scientists are trying to replace fat particles with calorie-free substances such as water, air or gels, while keeping the foods taste, smell and feel in the mouth the same. It is possible that small, stable, air bubbles designed to resemble oil droplets in terms of their size and physical properties could be used to produce a new generation of low fat foods, said the research leader, Dr Philip Cox. The team created its water-chocolate by bonding water particles with crystals of cocoa butter. It retains its taste - and even melts at 32-34C - because the particles are so small. A similar technique can reduce salt content in foods by up to 80 per cent. Water is hidden inside oil droplets so only their outer skin contains any salt. The team is hopeful its super porridge could soon go into production. It works through liquid changing into a gel when it comes into contact with acid in the stomach. Professor Ian Norton, who is overseeing the research, said: It remains there for 5-6 hours, so is perfect for between meals. We are well advanced with the work and are already talking to manufacturers about creating products based on our research. Experts say the research could lead to a new generation of weight-loss foods. Bombarding the public with health messages doesnt seem to be working so if we really are to avoid an obesity pandemic we need to open our minds to completely new solutions, said Dickon Ross , editor in chief of the Institution of Engineering and Technologys E&T magazine. Perhaps if we steer publicity budget into this research, the UK could develop an industry to lead the world. LES