If they don't stop gambling for a while, they will lose more often than they win. And those are signs that they are already experiencing a very severe gambling addiction because they don't eat immediately even though they are hungry. Even though eating is the most basic thing everyone feels, they will immediately eat and stop their activities if they feel hungry. We shouldn't experience things like that because it will harm our health and if we are not healthy, how can we enjoy those moments of gambling full of thrills and joy?
That should tell you how addicted they really are to gambling, after all if they can ignore their hunger and they prefer to keep betting their money this means that their physical dependency towards gambling is in fact many times stronger than the need they have to feed themselves.
And when a person reaches that point it is almost impossible to convince them they have a problem, and the only way for them to realize this is the case is to hit rock-bottom, and many times not even that is enough to convince them they have a problem.