Lots.
A sugar shunner can shun lots and lots and lots of sugar.
A practiced sugar shunner can shun the chocolate chip cookies someone offers her at the office, and the ice cream that's in the deep freeze at home.
A well trained sugar shunner can walk by platters of brownies and jars full of chocolates without a second glance.
Super sugar shunners can go down the candy aisle and the cookie aisle without adding anything to their shopping cart.
But if someone special should unexpectedly bring a sugar shunner some of her favorite sugar while she is working and very hungry, can the sugar shunner shun the sugar then?
Well...
No.