Well I know they can only eat small amounts of pureed foods or it all comes back up again. Weight loss will probably be quite dramatic and fast, so your partner will possibly be left with lots of loose skin, which in turn will make them feel bad about their appearance.
Alot of patients find the psychological effects of not being able to eat as much as they used to quite traumatic and may find this is the hardest thing to come to terms with. They can become quite depressed and irritable. The best way to support them is by eating healthily with them and trying not to consume the types of food they crave in front of them
If you have Sky TV, there's a regular programme on one of the Health Channels, called "The Fat Doctor". It's mainly focuses on one of the UK's leading Bariatric Surgeons, Dr Shaw Summers and his patients, who undergo Gastric Bypasses and Banding surgery.