Up your healthy fats (avocado, cheese, cottage cheese, yoghurt, olives, olive oil, oily fish like salmon, sardines, hummus)
Increase protein- 8oz steak instead of 6oz, keep chicken drumsticks, eggs, etc. in fridge handy
Add a smoothie/milkshake/protein shake if struggling to eat. When my MH is bad I use meal replacement when I am not hungry to regulate blood sugars.
Do some weights and build your bum etc. through squats. If you work your core that should help you gain curves in the 'right' places not the 'wrong' ones
Do strengthening exercises like swimming and pilates which tone you, instead of running or aerobics which makes you burn a lot of calories.
Mostly, people gain weight through eating junk but you can do it healthily.
Do you snack? if its low cal like fruit, add a yoghurt, a HB egg or a handful of nuts.
failing that, PEANUT BUTTER. I put on a stone clean eating and the culprit was PB.