It is possible to have no six-pack. The six-pack is a group of muscles located on the front of the abdominal wall. These muscles are the rectus abdominis, external oblique, internal oblique, and transverse abdominis. The rectus abdominis is the muscle that gives you the six-pack look. The other three muscles help stabilize the spine and pelvis and assist in breathing.
People can have different amounts of muscle definition in their abdominal area depending on their genetic makeup, body type, and amount of body fat. Some people may have very defined abdominal muscles but not a visible six-pack. Others may have a visible six-pack but it may not be as defined as someone with less body fat. And still others may have no visible six-pack at all.
Having a six-pack does not necessarily mean you are healthy or fit. It is possible to be overweight or obese and still have defined abdominal muscles. Conversely, someone who is thin or has very little body fat may not have a visiblesix-pack but could be extremely fit and healthy. So, don't judge someone's health based on whether or not they have a six-pack!