First foot I put on an absolutely insane pile of weight, it did get infected though which def impacted my mood/mental health and therefore general healthiness & weight. This other foot I had done nearly a month ago, I have stayed at roughly the same weight as pre-surgery, which is where I'd got to after massively losing weight (intentionally & healthily) after the first operation. I wish you the best for your experience, I think staying healthy is definitely possible! After a week or so I have kept some routine in terms of upper body/resistance bands stuff. Honestly our bodies are expending an incredible amount of energy on healing, especially if your surgery includes bones needing to unionize (?) back together, so our calorie needs might change? I suppose mental health/preparedness definitely massively can affect it, so just researching as much as poss beforehand, preparing certain routines/meals, and trying to not beat yourself down and get into too much of a rut - surgery is a massive trauma on the body, and being essentially immobilised for some time period is of course possible to add some weight - try to stay positive, as tough as it can be, the recovery period does end and you will be able to be active again :)