@simrin-- You're a great observer. I just read about the connection between anti-diabetic medication and leptin. Apparently. anti-diabetic medication increases leptin sensitivity in the body. So it does aid in weight loss and it is prescribed off-label for obesity.
The article I read also mentioned that some people with obesity have enough leptin in their body, but their body is unable to recognize it. So they never feel full and tend to overeat and gain weight. Taking leptin supplements doesn't help, because no matter how much leptin the body has, it doesn't work if it doesn't get recognized. Anti-diabetic medication can fix this to a large extent.