The easiest way to lose fat is to cause your body to use more calories than it takes in.
So if your daily calorie intake consists of 2500, and your usage is 2400, you will be gaining weight, same works for the other.
When you take less calories than what you spend, your body naturally starts to turn fat into energy and you begin the weight losing process...
Don't do diets, instead change your diet.
Don't eat ANY sweets (mars bars, snickers), don't drink sodas. Instead replace sodas with water, and replace sweets with a good belly rub and a reminder about what your goal is.
Sweets are useless and just have immense amounts of calories, for no real reason..
So basically.
Five steps:
1. No more unhealthy amounts of chocolate.
2. No more sodas
3. No more beer
4. Start using your calories (by doing anything really.. I would advise copious amounts of sexual activity)
5. Eat protein rich foods and vegetables. You will get your carbs from vegetables.. no need for bread, biscuits, spaghetti and similar things.
Hold onto these rules, and the more you do step 4, the less you will have to torture yourself by not eating really tasty food.. I reckon in a month you will look great (if you take step 4 really seriously)