Weight gain can be attributed to a number of factors, but in a nutshell if we eat more calories than we burn off, we will put on weight.

The energy density of the food we eat is very important when trying to lose or maintain weight. A low density food means that we can eat more of it and consume fewer calories. Oats are a great example of a low density high nutrient food - an average 40g serving is just 148 calories.

The calorie intake from oats comes mainly from non-refined carbohydrates, which are high in fibre and help to make us feel fuller for longer. Porridge has a low glycaemic index which means that energy is released slowly into the bloodstream which helps to keep us feeling satisfied for longer. Some cereals have extra calories because they have added sugar. They may also contain less fibre so we end up feeling hungry more quickly.