I agree with RedQueen. Special K is not all that healthy. Sure, it's low in fat, but if you look at the ingredients for the bars or the cereals you'll see it has added sugar, HFCS and other weird stuff. Here are the ingredients for the vanilla bar, from the Special K website: "Cereal (rice, sugar, whole wheat, wheat gluten, wheat germ, salt, wheat flour, malt [corn flour, malted barley], maltodextrin, thiamine hydrochloride, colour), sugar/glucose-fructose, fructose, dextrose, vegetable oil, hydrogenated palm kernel oil, rolled oats, wheat flour, sorbitol, milk ingredients, glycerin, applesauce, brown sugar, natural and artificial flavours, soy lecithin, calcium carbonate, salt, sodium propionate, tocopherols, BHT."
Special K is a highly-processed food that does an excellent job of marketing itself as healthy, but it's not a natural food. The cereals also have very little fibre compared to most cereals, so I doubt they'll leave you feeling full. I'm sure it's possible to lose weight on the Special K if you are eating less calories overall, but I would suggest a bowl of Kashi cereal or some steel-cut oats with fruit and honey over Special K. A really good cereal should have 4-8 grams of fibre per serving, while Special K only seems to have 2. I know the bars are nice because they're sweet but only have 90 calories, and they're definitely better than eating cookies, candy or a chocolate bar when you're craving something sweet, but again I'd have to say there are healthier options when it comes granola bars. Kashi has granola bars and I'd even say that the fibre-one bars are better, they have a lot of added sugar too but at least they have some fibre.