Just like most health issues, many different factors contribute to obesity. The factors most responsible for the obesity epidemic seem to be our genetics and the environment, and how they interact to create our eating behavior. To gain a deeper understanding of how they contribute to obesity, let’s explore the organ responsible for our eating decisions — the brain. The brain was built over millions of years of genetic evolution. The evolution of the brain (and its deeply ingrained behavioral patterns) depended on its ability to adapt to an environment that shared almost nothing in common with where we spend most of our time today. The first humans didn’t have Walmart, grocery stores, and restaurants around every corner — they had wild plants to forage and animals to hunt that may or may not be there the next day. To adapt to this uncertain food environment, humans and all other animals developed a highly motivating and rewarding relationship with food. As a result, humans and most other animals tend to eat much more than necessary in an attempt to store extra calories and other nutrients away for times when food is scarce. To put it more simply, we are wired to eat as much as possible when food is available.