Being a product of evolution, all mammals have developed a safeguard against times of famine. When food is abundant, we store excess energy in the form of fat. When food if scarce, our bodies can use the stored fat to make up the extra energy that is needed.

In this day and age, in first world countries, food is rarely scarce. So any excessive fat that we have is a bit "useless" (note: we all need a bit of body fat to function, especially women, so this is talking about fat beyond a healthy normal amount).

This means that:

• The excess fat needs to have a blood supply, which puts undue pressure on your heart

• The fat disrupts the way your body produces and uses insulin, leading to higher risk of diabetes

• The extra weight also puts more stress on your body in general, leading to more wear and tear: joint problems, feet problems etc

Ann additional thing to think about is where the extra energy is coming from. Foods that are high in saturated fats, salt, or sugar can have additional health detriments on top of the weight gain itself