Cut out all unhealthy foods such as chips, biscuits, cakes, crisps, sweets, sugar desserts but do allow yourself a couple of squares of dark chocolate as a treat.
Reduce fried foods to a minimum.
Boost your vegetable and fruit intake.
Drink water, or tea.
Do exercise; fast walking is very good or jogging if you like that. It's important to make up muscle, as muscle uses calories all the time even when you're asleep!
Most important, after the prom stick to this new healthy way of living.
By July you could easily lose a stone.