How to deal with sensitive overbearing Friend?

I have a very close friend who has become kind of overbearing. She is extremely tuned into her own emotions, and her overall health. She takes a very eastern approach to most things in her life, believing strongly in the power of foods and supplements as the source of and answer to all of life's problems. While I think her views are interesting, I don't feel the need to apply them all to my life. One particular issue right now, is my weight. I exercise all the time, am very conscious of what I eat and maintain what would be classified as an overall healthy lifestyle. Yet I can not lose weight. My girlfriend feels that she is an expert on this topic, and has done a lot of research, but I feel like she is starting to shove things down my throat as opposed to just making suggestions and letting me go. The problem is she is very sensitive so I feel like I can't just say back off. Any advice as to how to address this?