How can this salad dressing be fat-free?

Who's asking: Joanne Hanley, Chevy Chase, MD; me

Dinner with my friend Joanne last night included a new salad dressing she'd bought for its unlikely label: "CALORIE-FREE Creamy Bacon Dressing." Joanne, like me, comes from a long line of Irish-Americans with a healthy respect (not to say an unhealthy fetish) for bacon; we're not used to seeing the words "calorie free" juxtaposed with "bacon."

So we tried it. It wasn't bad, tasting mostly of vinegar and mustard. It was creamy, though -- opaque and white -- and smelled faintly of bacon, thanks to the imitation bacon bits on the ingredients label. For something fat- and sugar-free, it was a perfectly acceptable addition to iceberg lettuce. (Shut up. Iceberg lettuce is part of my cultural heritage.)

The question remains, how is this possible? It's the fifth ingredient listed, after the triple filtered purified water, the apple cider vinegar, the white vinegar and the dijon mustard (also vinegar-based): Cellulose Gel.

Cellulose is a biopolymer (i.e., naturally-occuring substance that can take many forms) that makes up the primary matter of plants. Cotton fibers are almost pure cellulose; cellulose is also the main component of green plants. It's water-absorbent and indigestible to humans, serving as bulk or roughage in food.

Cellulose gel in food serves as a fat substitute in dairy products, in particular. I haven't been able to tell what chemists make it from, and it hardly matters, since they're reducing plant matter to its most basic level. Cellulose gel could start as cotton, corn, algae or apples; it all ends up as the same stuff.

To enhance the illusion of creaminess, food chemists combine cellulose gel with other biopolymers, most frequently xanthan gum. Xanthan gum makes liquids thicker and stickier, and acts as a stabilizer. Xanthan gum is biological in origin, but formed by a chemical process, like cellulose gel.

The next question -- maybe not for this week, but I'm adding it to the list -- is whether these additives qualify as "natural." If anybody knows, chime in.