Pre-spinal surgery weight loss advice please

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Just to be clear I'm asking this for a friend who today has been told she cannot be operated on until she has lost weight. I want to help and support her, but obviously physical activity is very limited. She's very upset right now and I'm worried about her. She's not a member currently, but I'm hoping she will be eventually. I'd like the help from a place of support. Has anyone else been through this? Can any give me advice on how to start losing the weight she needs too? I'd love to hear other people experiences or friend people in this situation. Thank you xx