I am not new to diabetes & hav rapid weight gain since starting insulin & work out what can help weight gain with using insulin.

Insulin: And lowering your blood sugar are good, but they can stimulate appetite and weight gain. Make sure you're on as low a dose as possible, and pay extra attention to restricting calories and exercising more to lose weight rather than gaining. Also ask about glp-1 agonist therapy which can reduce glucose, lower Insulin requirement, and help w/weight loss.