It's not that simple. It's not always the number of calories we eat, but the type of calories that caused weight gain.
The biggest cause of weight gain is eating fructose. Fructose can only be metabolized (broken down) in the liver, and fatty acids are produced. These fatty acids then cause fat to build up in the liver, but also around the belly, and through your whole body. If you really want to lose weight.. you need to reduce refined carbs such as bread and pasta, eat more fresh fruit and vegetables and reduce the fructose you eat. Fructose is a natural sugar but it is found in fruit, maple syrup, honey, dates and if forms 50% of table sugar. It is also found in a very processed form in high fructose corn syrup and agave syrup. Check out this article which explains how to reduce your belly and body fat naturally http://superfoodmania.com/how-to-reduce-bodyfat-and-belly-fat-naturally/