Hello! I'm new here and I'm not a statistician but I would appreciate your inputs.

Is it possible to make a meta-analysis investigating results from various randomized controlled trials (i.e. one has a population of diabetic patients, another has hypertensive patients, another one has pre-diabetic patients, yet another has breast cancer survivors, etc. --- all of these patients are obese and are adults) as long as all of them have been done with weight loss as an outcome and almost the same intervention applied (behavioral counseling)?

I have been arguing with a research partner about it where she says it can't be done, that I'll have to analyze each group differently while I say that it can be done. Obviously, we're not statisticians so we're just going around in circles.

Would really appreciate everyone's input here. Thanks.