Good question ....

An average sized tomato contains 6g of carbohydrate - could this be the reason?
Toms are more carby and of course are a fruit not a vegetable they contain sugar and acids.

They do not get introduced until 1000 cals. It is only white and green up until then, with the exception of pickled red cabbage!

I guess it all depends on how carb sensitive you are - i've been having them when established in ketosis and they haven't knocked me out - would they still slow my loss even if i'm still in ketosis?
And also I've got the same question about onions????
From experience, I had lady few weeks ago who was on SS and had 2 cherry tomatoes every day, without my knowledge, this was all she had it was her first week and her weightloss was 1lb.

I know this wasn't AAM week but it showed how a couple of toms per day affected her loss.

Maybe this is one to run by CD but it has always been green and white - excluding root veggies or bulbs also.