Lower your calories will slow down your metabolism and obviously less will be going inside you. Both mean you will not be needing to go to the toilet as often as before. Your stool takes longer to create. Maybe 3 or even 4 days if you are severely cutting back. Weight loss relies to some extent on getting rid of the excesses through sweat, pee and poop. However this isn’t a cause for concern it just might means you may experience lots of weight loss followed by much less.