Great article here from The Times on how coffee can help with weight loss and fitness:
Scientists at the Australian institute of Sport have shown that if you drink it before a workout, the caffeine in coffee helps the body utilise fat effectively.
In another study, Dr Jason Tallis, a scientist at Coventry's department of biomolecular and sport science, it was found that drinking an espresso 20 minutes before you exercise can produce a 6 per cent improvement in your power output during endurance exercises, such as marathon running, swimming, rowing and cycling. This is because caffeine helps to release calcium stored in muscles, which in turn, boosts their power output. You can keep going for longer at a higher intensity and will burn more calories in the process.