Did you know that you are likely training your core every day without even realizing it. Most types of compound movements, such as squats, deadlifts, overhead presses, pull-ups, push-ups, running and even simply walking trains your core to some degree...
Forget the fad diet and quick fixes, the only way to loose belly fat for good is via causing a negative caloric intake. That is, either consuming fewer calories than before or burning more calories. But a better strategy, and the best one hands down, is doing both simultaneously - with a combination of nutrition and exercise.