Mixtures of fructose and lactose are useful for reducing caloric intake and glycemic index for individuals who are overweight, glucose-impaired, diabetic, or who just consume too large a fraction of their calories from "added sugars". The fructose/lactose sweetener is included in the daily diet as a one-for-one replacement for "added sugars" in various edible formulations without sacrificing quality of taste. Sucrose can be used as a replacement for all or part of the fructose in the claimed sweetener to increase sweetness or improve certain functional properties without substantially changing caloric value. The claimed mixtures of fully-caloric sugars work synergistically to reduce available calories and blood sugar concentration. Specifically, fructose interferes strongly with normal small-intestinal absorption of lactose and interferes moderately with sucrose absorption, while lactose interferes with normal small-intestinal absorption of both sucrose and starch. Unabsorbed di- and oligosaccharides pass into the colon and cause increased growth of healthful bacteria, making the new sweetener useful as a prebiotic. No gastrointestinal symptoms of sugar intolerance were observed when the claimed sugar mixtures were ingested at normal dietary levels.