No food makes in itself thick. Whether one does the "ability" to get fat, is primarily a matter of disposition. Who is naturally thin, can still exert so and will still never be significantly overweight. Who is inherently strong, however, will always tend to increase quickly, regardless of what he eats.
Especially greasy pizza is naturally through greasy ingredients, so primarily cheese, optionally also preserved in oil deposits. A Pizza Quattro Formaggi ( "4 cheese"), perhaps it with a dash of olive oil, that would be a prime candidate for a particularly greasy pizza. That pizza is greasy, but does not mean that one of them particularly rapidly increases, but it all depends on the individual metabolism and living conditions (physical activity, etc.), whether and how much of it intercalates the body in excess body fat.
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