Is eating making you hungry?

You eat too many 'bad' carbs

Sugary foods and processed carbohydrates, like white bread, white rice and low-fibre breakfast cereals, have a poor ability to fill you up, because of their high GI, glycaemic index. This means they're digested quickly and only raise blood sugar levels briefly, leaving you hungry again quite soon.
Beat it: Opt for slower-releasing minimally-processed carbs which fill you up for longer. Eg muesli, porridge oats, seeded or grainy bread and pulses, including baked beans.

Your diet doesn't have enough bulk

According to one scientific theory, we're satisfied by eating a given volume of food every day, not a particular calorie count. Choosing more foods with a 'low energy density', lots of bulk but not many calories, will achieve fullness without you getting fat.
Beat it: Include more fruits and vegetables, salads and potatoes or pasta without butter or creamy sauces in your diet. and fewer crisps, fries and fast food which have loads of calories in a small portion!

You're not having enough protein

Protein is more filling than either carbohydrate or fat, so take a look at how much of this nutrient you're eating. As a nation we over consume protein but there's a lot of individual variation and having one large portion daily might be less effective for hunger management than having two smaller ones.
Beat it: Make sure you have two separate small servings a day of lean meat, fish, Quorn or tofu.