.hi,can I lose weight by exersising without any diet?

I have lost weight that way in the past... After excersiing I find that I think more about what I eat anyway and tend to eat less.

Yes, you can lose weight by increasing your physical activity to the point that you are burning more calories than you are eating. However, there is an old saying 'You can't out train a bad diet'. A combination of healthy eating and exercise is the most efficient way to lose weight.