My sister struggles with obesity. At age 54 she decided that she was tired of the attitudes towards her at work and no promotions. Her direct supervisor did her a great service and told her that her size was holding her back from promotions in the company. Today that would not go well, but it just may have added many years to her life. She joined Weight Watchers that day. In 2 years she had lost 100 pounds and started to enjoy exercising on a daily basis. Another great thing happened. She was promoted to supervisor and got another promotion 2 years later. Seems not only did her body change affect others view of her, but it also affected her view of herself.
She is retired now and still keeps up the exercise and Weight Watchers meetings. Her former company still contacts her for consulting work and she is doing just fine. Only one downside to it all is the damage to her joints carry from all the extra weight for all those years. You can shake the family attitude towards you, but it will be extremely difficult to do. Changing your mind about yourself is very hard work that takes a long time to get done. Stick with it.