Kellogg???s Special K Challenge claims that by replacing two meals and snacks a day with Special K products, including cereals, protein shakes and protein meal bars, a weight loss of up to 6 pounds in 14 days will occur. ???First, a focus on quick weight loss just sets people up for the yo-yo diet cycle of losing and regaining that makes people fatter, not thinner.??? says Marsha Hudnall, MS, RDN,