The three fundamental body shapes mentioned above reflect the interplay of many factors, namely the environment, genetic and hormonal influence, race, age, fitness, height, build, lifestyle, metabolism, attitude towards food, preexisting conditions, medical history, drug use, and so on. Within these factors, your genetic makeup plays a significant role in whether you’ll end up overweight or underweight. In particular, you can be genetically predisposed to obesity if your family is known to have overweight members or relatives.
Among other factors, the influence of hormones on fat distribution is well documented. For example, estrogen is responsible for the traditional female characteristics (the hour-glass figure) by encouraging the pear-shaped fat distribution model. Estrogen compels the body to deposit fat on the buttocks, thighs, and hips, while testosterone encourages fat storage in the belly and upper body.
Furthermore, your digestive system and your metabolism rate aren’t the only processes that help balance your weight either; your nervous system can also play a significant role by secreting hormone like chemical agents. One such agent, known as serotonin, is the key substance that allows your nervous system to keep your body fat distribution in check. High levels of serotonin have been shown to reduce appetite. It convinces your brain to think that you’re satiated regardless of how much you’ve eaten, which affects the amount of food and fat you ingest. Furthermore, this neurotransmitter’s involvement in such processes as memory, depression, and sleep, enables it to manage a person’s body weight in many different ways.
Conversely, another neurotransmitter, endorphin, can encourage your appetite by sending signals to your brain to compel you to eat more. Depending on how much endorphins you have in your body, they can either induce or reduce the need to eat, with serotonin levels acting as a counterbalance of sorts.