This has to do with biologically determined male and female fat distribution patterns. For guys we put the weight on easiest in the lower abdomen, and the low back. Those areas are the first to gain and the last to lose it. There are biological reasons for it that have to do with receptor concentration in various adipose regions, but that is beyond the scope of a forum reply. You may have noticed women have the same problem with their hips and rear ends. The fat can and will come off though if you get your body fat percentages down low enough. Just know that those areas are the last to go. Also, some studies have shown that High Intensity Interval Training may have some preferential reduction of lower ab fat. Although, generally there is no such thing as spot reduction, it does appear that the High Intensity Interval training does hit the belly fat hard and at a faster rate then other areas, so if you aren't doing that, add it into your routine.