I lost 10 kilos in about three months. The way I did it was:
1. Watch your portion size. Put half as much on your plate than you normally do. If you're still feeling hungry wait for 20 minutes or spans if you still feel hungry eat a bit more.
2. Cut out processed foods. They contain salt, sugar and fat which are difficult to keep track of. So eat fresh meat, vegetables and fruit. Don't eat red meat too often. Chicken and fish are good.
3. Cut out sugary foods like chocolate bars, soft drinks, cookies, etc.
Giving up sugar can be difficult as it's addictive. If you persevere the urge for sugar will diminish quite quickly. Don't let people try to tempt you. Exercise is really good for you but, in spite of popular myth, it won't help you to lose weight. Stick with it and you'll be surprised how quickly you'll reach your goal.