It is hard to be a teenager... and it is even harder when MOM judges too.  I mean if you are actually "embarassed" about being seen in public with her.... you don't have to say a word.... you will simply "radiate" your judgement.  I am sure that this does very little for her self esteem.  What a fertile field for emotional eating disorder!

It can be extremely painful for a parent to watch a child put on weight.  Aside from health concerns, many parents worry about the social impact of being overweight.  For a parent who is in good physical condition, it can be especially difficult to understand a child's refusal to get help.  This often results in conflict and tension, none of which helps the situation.  You are right to realize that making a big deal about the issue will ultimately do more harm than good.  However, there are still things that can be done to help your daughter without alienating her.  Since she does not appear interested in taking charge of her own weight loss, it falls upon you as the parent to become the family nutritionist.  At 13, she is still quite young and not entirely in charge of her health or weight.  Parents can do a lot by understanding the causes of weight gain and some of the solutions.  An excellent book to read is "Ending the Food Fight" by Dr. David Ludwig.  You may also want to consult with a nutritionist yourself to get some ideas of how you can change your daughter's eating habits without her even realizing.  It may also be helpful to promote physical activity (without discussing the weight issue at all).  Exercise can make a significant difference to a child's weight and health.  Finally, understand that the best way to help any child is to establish the grounds for a positive relationship.  If a child feels supported, they are much more likely to eventually accept suggestions and help.