Robbie is an a.I. computer system integrated into the spaceship. It regulates your vitals. Its hardware is corrupt, thinking all humans are underweight and need to get to a healthy weight. No matter how fat someone actually is, it believes they still need to gain weight to get to a healthy weight. It thinks unhealthy foods are healthy. It will do anything to convince a human that they are skinny and need to put on some weight. He puts humans on diet plans that are actually fattening.