Switching diets?

Question
I'm in the process of switching my rats to a lab block diet. The vet said that rats aren't exactly the type of creature to starve themselves to death, and this is certainly true for one of my girls. Hershey's overweight and weighs 453g, compared to her cagemate who weights 250g. I thought I'd get them both eating the lab block diet before I work on Herhsey's weight, though.

Do you have any suggestions on making the transistion smoother? I've already tried mixing it in with other food (they ignored the blocks for the most part), feeding the blocks all day and giving them mini-meals (completely ignored the blocks) and so now I'm not giving them anything else in the bowl but for blocks. I've seem both of them nibble at the blocks before, but I don't think the smaller one (Kisses) touches them at all any more. I've been giving them both lots of treats, but not enough to serve as a meal. I've found that if I give them treats before sleeping, they won't nibble on the blocks at all and just wait for me to get up.

Help? I'm worried about Kisses not getting enough to eat.

Answer
I like the supplement my lab block with other things... they have an alloted amount that they can get of the supplemental diet and then when their supplement diet is all gone and they just have the lab block left, they have to eat their lab block before I'll refill the dish. My issue with lab block is that even though its a complete diet and much healthier for them; sure -- they're eating enough to sustain, but they're not really.. enjoying it. I've seen quite a few underweight rats - not overly skinny, but not heavy enough for me to be comfortable with, and certainly not heavy enough to handle it if they happen to get sick and start dropping weight. Call me crazy, but I'd hate to be on green beans and roast chicken all day every day; so I can kinda feel their problem with the lab block.

So.. I guess what I'm saying is that I don't like feeding a solid, lab block only diet. Make sure they're eating some of it for their protein needs if you supplement with nothing but carbs, but there are other forms of protein out there, and if you research rat diets and homemade mixes, you can find excellent alternatives that are a little more tasty for our furry friends.