No. Body weight has little to do with healing a diastasis. The internal abdominal muscles can be retrained and repaired regardless of your shape and size.  Often repairing your diastasis with functional core rehab gives you more energy and less pain which can help you become more active and kick start some other healthy habits if you are carrying extra weight.  Often clients are told or feel like they need to lose weight before they address the pain or weakness of their diastasis but we encourage clients to start rehab as soon as they know they have a diastasis.