We all point down getting fat from eating too much but wait there's more to just eating to match. There is a lot of reason why we gain too much. Let's see what are the factors that lead to obesity.
1.) Genetics - research says that genetic components are more likely influenced to gaining weight. For example, children of obese parents are much more likely to become obese than children of lean parents.
2.) Medications - there are some drugs can have weight gain side effects.
3.) Food availability - this is on top of the list in why people gain weight so much. You can see a lot of foods everywhere which is more tempting to eat. When you're craving sweets and or anything that affects your calorie count per day which will also lead to gaining unwanted fats. It is hard to control our eating habits if you see a lot of tempting foods everywhere.
4.) Leptin Resistance - is believed to be a leading factor in the pathogenesis of obesity. The problem is that leptin isn't working as it should in many obese people, because for some reason it cannot cross the blood-brain barrier (1)
5.) Eating habits - some people experience strong food cravings or addiction. This especially applies to sugar-sweetened, high-fat junk foods which stimulate the reward centers in the brain.