Almost everyone these days has heard of the glycemic index--a ranking of foods based on their immediate effect on blood sugar levels. It measures how much your blood sugar increases over a period of two or three hours after a meal.

But what's the Satiety Index? It's a system that measures foods' ability to produce satiety and fend off hunger; in other words, it's an even better indicator of their "stick-to-your-ribs-ness."

Developed by Susanna Holt, PhD, of the University of Sydney, the Satiety Index is based on a slice of white bread, which is assigned a value of 100. The satiety value of other foods is rated relative to the bread, with foods offering longer-lasting hunger abatement scoring higher. That means, on this scale, people trying to lose weight would choose foods with the highest numbers.

Looking at the differences between the two scales, you might suspect that there's more to satiety than the effect a food has on your blood sugar. Indeed, protein and fat both have minimal effects on blood sugar.

And here is where Dr. Holt's studies produced some real surprises. She and her hungry student volunteers demonstrated that foods high in fat made people want to eat more, even though we usually think of rich, high-fat foods as filling.

Dr. Holt speculated that the body responds to fat as something to be stored for a "rainy day," a period of scarcity, rather than something to be used immediately--so the gut doesn't stop sending hunger signals as soon, and we go on wanting to eat more.

Caroline J. Cederquist, M.D. is a board-certified family physician and bariatric physician specializing in weight management at the Cederquist Medical Wellness Center in Naples, Florida. She is author of Helping Your Overweight Child--A Family Guide, available at, DrCederquist.com, Amazon.com or by calling toll-free 1-800-431-1579. Learn more at Diet To Your Door