These pictures illustrate how the muscles are tightened during surgery and why abdominal muscle diastasis causes patients to have the full belly appearance which is unrelated to the amount of fat in their skin layer. When the muscles separate (usually after pregnancy, but normal wear and tear can do that too), there is a gap which is unfortified.
The arrows point to the borders of the recti muscles. Inbetween is a weak area. Contrary to popular belief, doing sit ups will just strengthen each individual muscle, but not bring the muscles back to the middle again.
When standing, the immobile insides of the abdomen (that’s fat and intestines) will shift and create a bulge. That bulge is not related to the subcutaneous fat that is treatable with liposuction or laser liposuction. Unfortunately, a significant diastasis does not have any minimally invasive options to repair, but requires a tummy tuck instead. In an obese person, the bulge will reduce with weight loss because the fat that surrounds the intestines becomes less heavy.