Hmm...I did WW years ago, leader was slim, at target weight but a right cow clearly struggling to maintain her weight and had all the sympathy of a sociopathic pirahna. She left and was replaced by a lady who was not as slim, but still in the range allowed by WW, and she was SO much more helpful (and also stamped out the thin bashing that went on in that class), talking about how it's not always easy to stay at target and making healthy food choices with your points, which the other one NEVER did, she talked about surviving off coffee and fags and starving yourself all day so you could have a plate of chips...
I joined SW after I had my DD and liked the diet plan, such as it is, and I liked the emphasis on increasing activity. the consultant at my local group is about a size 16 I would guess, but she used to be MUCH bigger and has her before and after photos around the room. She's a very attractive confident lady who dresses beautifully and she frequently addressed her own weight in sessions.
What she said was, her original target weight had been 2st less than she is now, however she struggled to maintain that and ended up putting all her loss back on, BP shooting back up, aching joints etc. When she returned to SW and ended up becoming a consultant, she decided to maintain at a higher weight, she is happy with her looks and is healthy and active in the "overweight" category.
I think that's a good approach to be honest, I live in a poor area and the majority of the people in the group were obese and had a LOT of weight to lose. Lots had lived on convenience food all their lives and never exercised, so had lots to learn about healthy eating and activity.
Some weeks someone would admit to feeling despondent about the mountain they had to climb, and she would remind the class we were there to improve our health and have a long happy life. She'd say stop thinking you have to fit into a size 10 skirt, instead think how much easier it will be to move around when you've lost a couple of stone, how much happier you'd be if you could bend down to pick up your grandchildren, etc., and that a nice side effect of that will be that you can buy a nice dress in a size 18 for your son's wedding or whatever.
I'm a HCP and think that's a good way to help people change their health behaviours, I used to leave feeling motivated and we talked a lot about food, recipes, how to deal with feeling blue and wanting to eat. I had a stone to go then went back to work and couldn't make the groups anymore but once I've had this baby I'll rejoin that group to get my pg weight off and hopefully a bit more besides.
Sorry for rambling on so long, I guess I'm trying to say that some weight loss consultants may not be slim, but they have still succeeded in losing a large amount of weight and keeping it off, so have a lot of wisdom to share and can be really supportive to help others make permanent changes.
I do understand though if you are going along to lose a couple of stone to fit back in your bikini you may be a bit nonplussed to be thinner than the person in charge :) just keep an open mind, there will be crap fat leaders and crap slim leaders, as well as brilliant ones of all sizes. It is the same diet whoever delivers the sessions but my WW experience showed me the group leader's attitude does make a difference.