Yes, Jennifer Hudson is actually a size 0 as she claims, because she looks very skinny. She has lost a lot of weight lately, and she talks about controlling what she eats. She is an honest person, so when she says that she is a size 0, I believe it. Either way, she is beautiful.
Jennifer Hudson may be a size 0 in some clothing brands and styles, but different clothing is made larger or smaller and while she isn't big by any means, she also isn't anorexic type thin. She is likely a bigger size than a size 0 in some clothing brands today.
Jennifer Hudson garnered a lot of attention and press for her weight loss, which was part of a spokesperson deal with Weight Watchers, and has since claimed to have slimmed down to a size 0, which is pretty much physically impossible given the fact that she is naturally svelte. She's doing so with the best intentions, but she's setting an impossible standard for women.
Dress manufacturers can put whatever size they want on clothing. In earlier years, there was a kind of standard size chart that was related to weight, I think. Manufacturers hit on the idea that they could artificially appeal to a woman's good feelings about herself by keeping the clothing's actual size the same but labeling it as a smaller size. This practice has truly reached absurdity when women begin to report a small size when they clearly are not that small. To report a size 0 seems idiotic, unless Jennifer Hudson meant it as a joke. Of course she can claim to be any size she wants, but everyone can see how big she is. I think manufacturers have carried this too far.
Without question Jennifer Hudson has lost a lots of weight and looks great, she has not made it down to a size zero. When she started her weigh loss program she was size 16 and has lost lots of weigh and maintained the loss over the past five years. Several designers have guessed Ms. Hudson's dress size in the two to four size range.