Susanna Holt, PhD, has developed the Satiety Index, a system to measure different foods' ability to satisfy hunger. A fixed amount (240 calories) of different foods was fed to participants who then ranked their feelings of hunger every fifteen minutes and were allowed to eat freely for the next two hours. Of all the foods tested, potatoes were the most satisfying.

How full did that meal you just ate make you feel? Did it satisfy your hunger, or did it make you feel like you'll need a snack later?

Now a new tool is available to measure the hunger fighting power of certain foods and help with blood sugar control.

Studies by Australian researcher Dr. Susanna Holt and her associates at the University of Sydney have developed one of the most exciting diet concepts ever. Called, the "Satiety Index," Holt's tool ranks different foods on their ability to satisfy hunger.

Holt drew up the Satiety Index by feeding 240-calorie portions of 38 different foods to volunteers. The foods were served from under a hood to minimize the influence of appearance, and, if possible, they were served at the same temperature and in the same size chunks.

After eating, the volunteers told the scientists what their appetite ratings were, but they were not allowed anything else for the next two hours. Then, after two hours, they were then allowed to eat from a small buffet, where the scientists measured how much they nibbled from a variety of other foods. Their consumption was closely monitored, and every 15 minutes they were questioned about their hunger to see if their subjective impression of satisfaction matched their eating behavior.

Using white bread as the baseline of 100, 38 different foods were ranked. In other words, foods scoring higher than 100 are more satisfying than white bread and those under 100 are less satisfying.

What Really Satisfies?

Holt found that some foods, like croissants, are only half as satisfying as white bread, while boiled potatoes are more than three times as satisfying, easily the most satisfying food tested. But potatoes in a different form—French fries—did not score well. This type of information can have important implications for those wanting to lose weight.

The chemical components of a food is one of the factors that determines how it ranks on the index. "Beans and lentils, for example, contain anti-nutrients which delay their absorption so they make you feel full for longer," says Holt. "Roughly speaking, the more fiber, protein and water a food contains, the longer it will satisfy. But you have to look at each foodstuff individually—and that is why we think our index will be so useful."

Another thing that makes a food satisfying is its sheer bulk. "You can eat an awful lot of popcorn without taking in a lot of calories," says Holt. "It may not weigh much, but it makes your stomach feel full just because it takes up so much space. Oranges come out very high on the index for the same reason—but orange juice probably wouldn't, even though it has the same number of calories."

It is, in fact, the size, bulk and blandness of potatoes that may account for much of its high satiety. Their "portion weight was up to four times greater than the other foods [for the same caloric content]," Holt and her co-authors note in a paper published in the December 1996 issue of the European Journal of Clinical Nutrition.

As a group, fruits ranked at the top with a satiety index 1.7 times more satisfying, on average, than white bread. Carbohydrate-rich foods and protein-rich foods deter nibbling almost as well. Holt warns, however, that there are big differences between the satisfaction values of individual foods within the same group.

"You can't just say that vegetables are satisfying or that bakery products aren't, because there can be a two-fold difference between two similar foods," says Holt. "We found that bananas are much less satisfying than oranges or apples, and that wholemeal bread is half again as satisfying as white bread [157 compared to 100 respectively]."

This too can be valuable information to the weight conscious. "A diet which simply recommends cereal for breakfast overlooks the fact that muesli is only half as satisfying as porridge [oatmeal]," she adds.

Some Surprises

In general, the more satisfying a food felt, the more effective it proved as a nibbling deterrent. But even here there were some surprises.

"Fatty foods are not satisfying, even though people expected them to be," says Holt. "We think the reason is that fat is seen by the body as a fuel which should be used only in emergencies—it stores it in the cells instead of breaking it down for immediate use. Because it doesn't recognize the fat as energy for immediate use, the body does not tell the brain to cut hunger signals, so we go on wanting more. Carbohydrates are the opposite—they raise blood glucose so the body knows it has gotten enough fuel."

Jellybeans also scored higher than expected. Volunteers fed jellybeans did not feel satisfied, yet they ate very little afterwards. This resulted in the sweets getting a satiety rating of 118—higher than that of muesli and yogurt and almost the same as white pasta.

"I suspect the reason that the jellybeans came out so well was that they made our volunteers feel slightly nauseous," says Holt. "We'll be doing some research on that one—if we can persuade people to act as volunteers!"

A Few Words of Advice

Holt is concerned that there may be some confusion in the interpretation of her study's findings. "The Satiety Index scores reflect the total amount of fullness produced by the set portions of the test foods over two hours—i.e. short-term satiety. Although most foods with high Satiety Index scores kept fullness relatively high for the whole two hours, there were a few exceptions," Holt notes.

"The fruits were served in very large portions, but fullness dropped off quickly towards the end of the second hour, reflecting the rapid rate of gastric emptying (oranges and apples and grapes are mainly sugar and water)," she adds.

"Many 'health-conscious' dieters," she continues, "will eat a meal based on several pieces of fruit and some rice cakes (in Australia anyway) and then wonder why they feel ravenous a few hours later. These kinds of extremely low-fat, high-carb meals do not keep hunger at bay because they are not based on slowly-digested carbs and probably don't contain enough protein. A dieter would be better off eating a wholesome salad sandwich on wholegrain bread with some lean protein like tuna or beef and an apple. This kind of meal can keep hunger at bay for a very long time."

What About Sugar-free Drinks? Does drinking sugar-free beverages rather than those loaded with sugar help you cut down on the total amount of calories you take in during a typical day? Or do they just make you hungrier? The answer, surprisingly, is neither. Researchers at the University of Sydney in Australia compared the effects of equal volumes of sugar-rich and sugar-free beverages on feelings of hunger and fullness and the free consumption of a palatable, fat-rich snack. Eleven healthy men drank equal amounts of sugar-rich cola, sugar-free cola, and mineral water in random order on separate mornings. Then, 20 minutes later they could snack on all the potato crisps they wanted for the next hour and one-half. Then they got a buffet-style lunch. All the while the researchers covertly recorded what the men ate, and at the end of the day they completed a weighed food diary. Each drink initially decreased hunger to a similar degree. The potato crisp intake was not significantly different for the three drinks. The amount of calories in the crisps and lunch were also not significantly different. "By the end of the day, total energy intakes were similar for the three test conditions," they concluded. "Therefore, the low-calorie/low-sugar drinks did not facilitate a reduced energy intake by the lean, non-dieting male subjects."



The Work Continues

Holt now works as a research scientist with the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia's largest scientific research agency, and is continuing to develop the satiety index.

"We've just done a short study comparing the satisfying power of different breakfasts," she writes of her, as yet, unpublished work. "Two high-fat breakfasts of fried eggs and bacon and toast or croissants and jam were much less filling than two equal-calorie high-carb breakfasts which were either rapidly-digested (cornflakes with sugar and toast and jam) or slowly-digested (All-Bran with banana slices, toast and margarine)," she adds.

Holt is also interested in how foods affect mood and alertness. "The two high-carb breakfasts tended to improve alertness to a greater extent than the two high-fat breakfasts. Also, because the subjects were not completely satisfied by the two high-fat meals, they tended to be grumpy and a bit more aggressive/disappointed."

Additional studies of satiety among children are also being planned.

Clearly, future research is warranted and Holt hopes to do it. Eventually tables showing the ratio of satiety to energy will be developed as a tool in planning diets for weight loss or gain. This way we can minimize our hunger pangs and make it easier to stay on our diet programs.

The Satiety Index Each of the following foods is rated by how much food people ate after consuming them to satisfy their hunger. All are compared to white bread, ranked as "100" Bakery Products Carbohydrate-Rich Foods Croissant 47% White bread 100% Cake 65% French fries 116% Doughnuts 68% White pasta 119% Cookies 120% Brown Rice 132% Crackers 127% White rice 138% Snacks and Confectionary Grain bread 154% Mars candy bar 70% Wholemeal bread 157% Peanuts 84% Brown pasta 188% Yogurt 88% Potatoes, boiled 323% Crisps 91% Protein-Rich Foods Ice cream 96% Lentils 133% Jellybeans 118% Cheese 146% Popcorn 154% Eggs 150% Breakfast Cereals with Milk Baked beans 168% Muesli 100% Beef 176% Sustain 112% Ling fish 225% Special K 116% Fruits Cornflakes 118% Bananas 118% Honeysmacks 132% Grapes 162% All-Bran 151% Apples 197% Porridge/Oatmeal 209% Oranges 202%

Table adapted from S.H.A. Holt, J.C. Brand Miller, P. Petocz, and E. Farmakalidis, "A Satiety Index of Common Foods," European Journal of Clinical Nutrition, September 1995, pages 675-690.

Update NutritionData.com has just published on that site a self-directed diet that uses what it calls the "Fullness Factor" at http://www.nutritiondata.com/fullness-factor.html. Ron Johnson, who together with his wife, Lori, developed NutritionData.com, explains the Fullness Factor concept in email to me, part of which I except below because it clarifies what they publish on the website: Volumetrics) to help establish additional data points or constraints, which were then used to create the current FF formula. Sue Holt's study played an important role in the Fullness Factor concept, because it's the only published study (to our knowledge) that provides quantitative observations of satiety along with nutrient composition for a reasonably wide variety of foods. Modeling this data set alone, however, proved to be problematic, as it is still limited in number and doesn't represent the full range of foods that humans consume. We consulted many other studies and published observations (such as Barbara Rolls's) to help establish additional data points or constraints, which were then used to create the current FF formula. There are at least three criticisms of the Fullness Factor that we readily acknowledge: The formula doesn't take into account all known contributing factors for satiety.

The formula is derived from a small data set.

The data set is based on subjectively reported, rather than directly measured, criteria. The Fullness Factor is our first pass in establishing the concept that the satiating effect of a food can be reasonably well predicted from commonly available nutrient values. We have not published a book or tried to sell this concept. We are merely giving our web visitors free access to FF calculating tools to allow their own experimentation. Our site sees approximately 500,000 visitors per month, which undoubtedly includes some obesity researchers. Hopefully the presentation of our ideas will encourage additional studies that will allow this concept and formula to be further improved. I have a great deal of respect for the amount of GI research that Jennie Brand-Miller has done. I believe that GI and GL are invaluable markers for carbohydrate evaluation. As a scientist and athlete, I've used GI values to help guide my own dietary decisions for more than 10 years. However, the general public (or at least the general American public) has tried to take GI beyond its original premise. In our opinion, it's not a complete enough indicator to be the entire basis for a diet. Of course, neither is/was the whole “low carb” idea. Our goal is to create or help create a simpler way for the average person (who may not even understand what a carbohydrate is) to evaluate foods. FF is not the complete answer, but we believe it's at least an improvement over simple caloric density. And when we combine FF with our nutrient-density-based Rating, as we do on our Nutritional Target Map (described on http://www.nutritiondata.com/better-choices-diet.html), the resulting food recommendations fall fairly well in line with most respected dietary plans (i.e., higher reliance on fresh fruits, vegetables, fish, and lean meats; lower reliance on sugars, fats, and processed foods). Our calculations may never replace a knowledgeable dietician, but we hope they help bridge the gap for those without access to that knowledge and assistance.

This article appeared in Diabetes Interview, May 1998, pages 1, 12-14. It was originally published in a different form on this Web site and subsequently in a somewhat edited form on John Walsh's site. The (Cleveland) Plain Dealer reprinted this article in its June 1, 1998, issue.

Bibliography:

Arnot, Robert. Dr. Bob Arnot's Revolutionary Weight Control Program. (New York: Little, Brown and Company, 1997), 305 pages. Probably the first weight control book to make use of the satiety index. See chapter 5, "Turn Off Hunger."

Holt, S.H., Miller, J.C., Petocz, P., Farmakalidis, E. (Department of Biochemistry, University of Sydney, Australia.) " A satiety index of common foods. " European Journal of Clinical Nutrition, Volume 49, September 1995, pages 675-690.

" European Journal of Clinical Nutrition, Volume 49, September 1995, pages 675-690. Holt, S.H., Brand Miller, J.C., Petocz, P. (Department of Biochemistry, University of Sydney, NSW, Australia.) " Interrelationships among postprandial satiety, glucose and insulin responses and changes in subsequent food intake. " European Journal of Clinical Nutrition, Volume 50, December 1996, pages 788-797.

" European Journal of Clinical Nutrition, Volume 50, December 1996, pages 788-797. Holt S.H.; Sandona N; Brand-Miller J.C. (Department of Biochemistry, University of Sydney, NSW, Australia) "The Effects of Sugar-free vs Sugar-rich Beverages on Feelings of Fullness and Subsequent Food Intake." International Journal of Food Sciences and Nutrition Volume 51, January 2000, pages 59-71.

The Satiety Index Elsewhere on the Internet:

"Diet Tips—The Satiety Index," reports on studies by researchers at the University of Sydney in Australia for National Bodybuilding & Fitness zine. The article says in part, "Food weight appears to be the determining factor. A portion of food that weighs more than another portion of food of equal caloric value is more satisfying. For example, boiled potatoes rated very high on the index, foods like hard candy (high sugar foods), or candy bars rated very low. Extremely high fat foods like cheesecake also rated badly, however some foods with moderate amounts of fat, such as lean steak, rate fairly well....A quick way to determine weather a food would have a high satiety index or not is to look it up in your calorie book and compare the calories to the portion size. If a 4 ounce portion of food (about 120 g.), has over 250 calories—avoid it." http://nbaf.com/nbaf/se6pgc.htm#a

"Weighing in the fullness factor," the Web site of the Toronto Vegetarian Association, quotes an article in Spectrum, July-August, 1996, page 5. The article says in part, "According to their investigation, the most satisfying foods were high in fibre. These included such items as whole grain products, potatoes and fruits. Foods high in fat were the least filling.Ironically, the tastiest foods—those high in sugar and fat, like sweet bakery products—were the least satiating. That's because volunteers reached their caloric limit for these foods before they'd eaten enough to feel satisfied. In real life, there may not be a scientist looking over our shoulder to prevent us from going overboard on calories, so the tendency is to eat until satisfied, and pay the price in being overweight." http://www.veg.on.ca/newsletr/novdec96/news_dec96.html#weight

The report where I first read about the satiety index, "Carbohydrates in Human Nutrition; Interim Report of a Joint FAO/WHO Expert Consultation, Rome, Italy, 14 to 18 April 1997," says in part: "Two indices of carbohydrate foods based on their physiologic functions have been proposed. A recently suggested satiety index [citing reference 53, which is Holt, S.H.A., J.C. Brand Miller and P. Petocz. 1996. Interrelationships among postprandial satiety, glucose and insulin responses and changes in subsequent food intake. Eur. J. Clin. Nutr.,50:788-797] measures the satiety value of equal energy portions of foods relative to a standard, which is white bread. The factors which control food intake are complex and satiety needs to be distinguished from satiation. Nevertheless, investigation of satiety indices of foods is considered an interesting area of future research, which, if validated, may aid in the selection of appropriate carbohydrate foods to promote energy balance. A more established index is the glycemic index which can be used to classify foods based on their blood glucose raising potential." The URL is ftp://ftp.fao.org/es/esn/nutrition/carboweb/carbo.htm

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