Dear SoPogirl,
I have never known anyone to do so, but have heard of people who lose weight to donate. I'm always concerned about their long-term ability to maintain the lower weight with healthy diet and exercise. Living with one kidney may be riskier for individuals who are more likely to develop obesity related health issues.
Has the potential donor discussed this with the transplant team? Other than weight, has the potential donor been evaluated and found to be suitable?
Regardless of the possible donation, an overweight person would be well off to control their weight, to protect their own health in the future.
I'd encourage the potential donor to talk with the transplant team and with their own physician to discuss the best ways to manage weight.
Love, elephant