Eating 1000 calories only wont do anything bad. Ofc excercise will also help you lose the weight but don't worry it's only 2 weeks. But it entirely depends on your age height and everything so idk how much you can loose weight but 1000 is definitely the minimum calories. Besides, you don't need to eat 1000 though just 500 calories less than how much you eat rn and that alone is plenty. That's healthy calories reduction. But if you're really worried about effects of 1000 calories dw I eat under 1000 have been for long time and work 5 days 38 hrs a week (i work at hospital emergency department so I barely have time to eat with alot of walking a lot of rushing never a dull moment) and I'm a okay.