Worried about a good friend of mine and about her health

Hi I am really worried about a good friend of mine she has gained a lot of weight and it’s starting to really affect her health. She used to be my size and I’m not an overweight person but I’m not skinny either I’m in the middle and I keep myself fit and active but my friend over time has really gained a lot of weight she can hardly walk can’t keep up with me anymore more and I’m worried. The issue is I want to raise my concerns with her but we are both on the spectrum and I don’t know how to mention it to her without out upsetting her I’m also worried that she might take it the wrong way. I’m also afraid that if I don’t mention anything to her that she will end up having a heart attack or something. Is there any advice anyone can give me on here?