Yes. Carbs are designated as Favorable or Unfavorable. You're told to limit your Unfavorable carbs to no more than 25% of your meals. For instance, a 4-block supper could have 1 block of rice and 3 blocks of broccoli. 4 blocks of Favorable carbs is a large serving, and it's easier to eat the smaller bulk of an Unfavorable block; the biggest complaint new Zoners have is that it's difficult to finish all our veggies.
But if you don't want to eat any Unfavorable carbs, you don't have to. (Sears even recommends that you avoid Unfavorables for the first week or two of the Zone, to kick-start your metabolism.) Optimally, you would eat only favorable carbs, no grains or legumes or root vegetables or alcohol or sugars. ('Utopia' is Greek for 'Boring')
That said, a certain amount of GLA is also recommended, and that can only be eaten, in food form, in a 3-block serving of steel-cut oatmeal.
It is possible to get your RDA of GLA in the form of primrose or borage oil, but most Zoners find life more enjoyable if we allow ourselves to indulge in trace amounts of cereal, rice, beans, potatoes, bread, wine, ice cream.