
As an Athletic Trainer AND Personal Trainer I am providing information that was presented to me in my college classes, certifications, internships, and fellow personal trainers... Because if you state that you can do moderate abdominal work every day, then you are saying that you can do moderate work every day of all your muscles, and as a personal trainer you should know that's not true...
"The 'spot exercise' fallacy assumes that if you have fat deposits on your abdominals, exercising the muscles underlying the fat will make it go away. A client who does 100 sit-ups a day for a flabby stomach will increase muscle endurance for the abdomen,but will not burn off the fat in that area." (ACE Personal Trainer Manual, p. 308)
When you train your abs for growth, you are primarily training the fast-twitch muscle fibers, the ones built for power, not endurance, and the ones that have the most potential to develop. Fast-twitch muscle fibers require more recovery time than slow-twitch muscle fibers because they are, by nature, less resistant to fatigue. Training abs every single day is really training your abs to be more resistant to fatigue.
If you train your abs before they have recovered from a previous workout you are actually hampering your progress. Your abs, just like any muscle, need time to recover.
On top of that, he shouldn't be focusing on doing abdominals every single day, he should be focusing on doing nutrition every single day because that's how he's going to get the fat off the stomach... Plus all he asked was why was he getting more results in the rest of his body rather than his stomach... not how to reduce it...
Not to mention that we would have to also consider that he may have an anterior tilt of the pelvis allowing his core to be 'pryed' open allowing his abdominals to protrude, so that would also have to be worked on...