Another good thing to do is to go to
channel4.com/bodies and log into 'Healthchecker' and then take the 'BMR' test. It will tell you how many calories you burn during the day without any exercise and therefore you can then find out, if you want to loose weight and can't exercise for a few days, how may calories you should have. The best thing to do is... If it says you burn 1550 calories a day, only have 1400 and you will already be losing weight.
But that won't make you lean, you'll have to do exercise and the best thing to do is when you go to the gym just do cardio one day and the nest just do weights. When you do cardio, have green carbs like veg and fruit but when you do weight work outs have starchy wholemeal food. But eat more than the 1400 that you were eating as you need the energy.
Also ALWAYS have recovery food after a workout which means you need something that has protein but also a little bit of sugar in to revamp your body... such as a banana or even a glass of chocolate nesquik and milk...have this between 20mins of your workout session.
GOOD LUCK....Just put your mind to it and you'll do it.