Extra fat can build up behind the ab wall, giving more pressure to bulge out. And mostly to the middle or lower ab region. People can look somewhat muscular and trim but still have that extra layer of fat. Happens a lot to folks who have lost a lot of weight, though that lower belly seems to still hang (no pun) around. Or to a lot of normal weight (what ever that is) people. If the main cause where gas bloating if would affect the middle and upper wall as well.
And as mentioned by (and more likely) Tbombz, it may be a genetic storage for extra body fat. Tends to get more serious as one ages.
Fasting also calls on muscle mass, as well as body fat, fore maintaining daily body energy and functions. Though controlled fasting can help the body in a lot of ways, probably not a great ideas to do more than a short one day fast for the BB'er. And not he best way to lose a targeted area like the lower belly.
A vacuum exercises to hit the muscles and supporting muscles around and behind the ab wall may help. During the day you would bend at the waist and try drawing the stomach up and in as tight as you could get it. Exhale drawing in, inhale when releasing. High reps for these, beginning at 12 or so and working to 30-40 or more. Once learned, the vacuum is done at a fast pace. Fix your mind on drawing in the complete ab wall, upper, middle and lower. This hits the abs like standard exercises do not.
Could also consider muscle control for a superior ab workout. Like ab roles, isolation one side and that the other, ab ropes, etc. Great stuff when taken the time to learn. True mind body connection. Good Luck.
