1 pound of fat is roughly 3500 calories. Depressing thought. basic metabolic rate around 1500 for a guy(again this varies but stay with me). Add in a session at the gym(4 mile run/a few weights) and you add 5-600 calories.
Cycle to the gym and back, take the stairs not the lift, walk to the tube/train and leave the car, and you're up to 2500 a day.
Leave a deficit of 500 calories a day and you will lose a pound a week- maybe more as your body builds muscle which will increase your metabolic rate.
You might be able to crash diet a few pounds by starvation but your body will have its revenge by slowing down your basic metabolic rate(it very sensibly assumes famine and therefore stores everything as fat....) resulting in you putting weight back on as soon as you even look at a slice of bread.
Take it slow and steady and the weight will stay off and you will stay healthy with plenty of energy.