Specifically, your sex hormones. Testosterone and estrogen are two of the biggest drivers of fat storage—they’re the whole reason that men and women tend to have different body shapes when it comes to chub. Biologically female bodies stash the stuff in thighs and butts, whereas male bodies tend to pack pounds onto the stomach. This is also partly why men tend to have more cardiovascular problems. Abdominal fat exacerbates metabolic issues and triggers all kinds of metabolic changes that have a negative impact on your cardiovascular system.The way your body does this is way more complicated than just that. For example, too little testosterone has the same effect as too much testosterone! To learn the effects of hormones on body fat, scientists study the ways hormones change, specifically, at puberty and menopause, during gender reassignment therapy, and under abnormal genetic conditions. Read about the role of hormones in distributing your body fat at Popular Science.