To add to Archimedes comments, it is difficult for anyone (man or woman) to add a lot of muscle mass while running a calorie deficit to lose weight, as the body tends to burn protein for energy, rather than creating new muscle tissue.
Also, fat is considerably bulkier than muscle. Take a look at the photo at www.dailyspark.com/blog.asp?post=quiz_how_
Bulk in the belly is because of fat stored there, not muscle.
In any event, the abs are a long thin sheet of muscle. Even if over a period of say 12 months, you were able to add 50% to your abdominal muscle mass, because it is a thin sheet, you aren't going to be adding noticeably to your waist measurement.
A strong core is important for posture and balance, and actually makes other forms of exercise easier. And as Archimedes said, strength training is a significant fat burner. You SHOULD definitely be including core exercises in your overall strength training program. Although it should be noted that burning fat is an all-body process, and core exercises won't specifically help you target body fat.
Your trainer is wrong in her concerns, and wrong in her advice on structuring an exercise program.
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.
| current weight: 178.0