The simplest reason why we gain weight is that we eat more than what we burn. Anytime we eat something, our body converts it into sugar. This sugar than is converted to energy. This is the basic principle on which our body works.
However, if we do not use this energy by working then it is stored in the body as fat and is used as a resource when there is lack of energy. But if we keep on eating like this daily without using the produced energy then this gets adding up in the stored fat and as a result we gain weight. In order to lose weight naturally we have to maintain the intake and output. We have to eat what we can burn. If we eat more than what we consume than we would sure gain weight.
In the previous time, there was lot of physical labour, our ancestors had to work more to get the food and thus they never faced the problem of obesity. However, now with the changed lifestyle and higher standards of living there is no dearth of more rich food and that too is readily available. We don’t like our ancestors have to grow our food neither we have to grind the ingredients that we add in our food. We now have ready to eat things demanding no labour from us.
We also now live in an atmosphere surrounded by too many food joints offering high calorie food. Also, in the fast paced life we depend a lot on the packed and preserved food products that have more calories than the natural foods.