Satiety Solutions

HEALTH/NUTRITION

Satiety Solutions

By Cindy Hazen
Contributing Editor

Ask the average consumer the definition of satiety and chances are they would say, “I don’t know. What’s that?” The more educated might link it to satiation and say: “Oh, being full.” Even Merriam-Webster fails the scientific community by defining it as: the quality or state of being fed or gratified to or beyond capacity. Yet for researchers and the food industry community, satiety does not necessarily mean full.

Mark Friedman, Ph.D., associate director, Monell Chemical Senses Center, Philadelphia, clearly sees a difference between satiation and satiety. “Satiation is the immediate consequence of eating food that makes you stop eating,” he says. “Satiety is the state where you no longer want to eat, but it’s not associated with any particular bodily experience.” While a full stomach might in fact be a signal to stop eating, there are a myriad of other experiences that enter into the equation. Bodily functions

Many of the physiological changes that produce satiety go as unnoticed as a slight rise in blood pressure. “There are theories concerning release of various gut peptides, or gut hormones, that people believe might act as a signal for this satiation part,” Friedman says. “There are also other data that suggest it may involve changes in metabolism because you start absorbing nutrients very quickly during a meal. Changes in the body metabolism and energy metabolism might provide a signal for satiation as another almost-immediate effect of eating food.”

Alternatively, what triggers hunger? “There’s a period where you don’t feel full, but you’re not thinking about eating,” Friedman explains. “At some point, you want food. The best explanation for that process is that you consume some energy, you consume some nutrients and now those nutrients are being processed. Eventually, that process might run its course, and then you get hungry. Our work focuses on the idea that your body can monitor the energy that’s derived from the fuels in the foods — fats and carbohydrates, and under some circumstances, protein — that are used to make energy to fuel bodily processes. There’s some aspect of that generation of energy in a biochemical sense that’s producing a signal to eat or not eat. When you’re in the process of making a lot of energy, you’re satiated. When you process those fuels, and now you have to rely on what you’ve stored away, which is doled-out in a much-more-stingy way because you need it to last between meals or even a prolonged fast, then your production of energy declines and you want to eat again. Basically, what we’re saying is that you’re monitoring the calories in the sense of calories realized, actual energy generated by these fuels.”

How fuels are burned depends on what the body is set up to do, according to Friedman. In a diet with mixed fat and carbohydrates, which is what most people eat, the body primarily uses for energy and the fat is stored. In a high-protein, low-carbohydrate diet, such as the Atkins diet, it burns stored fat, as well as dietary fat. If carbohydrates are added, the body releases insulin. “Insulin inhibits the burning of fat,” Friedman says. “In a sense, a calorie is a calorie, but it really depends on what the metabolic background is whether the fat calories will be realized as readily as carbohydrate calories would be.”

Though the metabolic pathways for carbohydrate and fat metabolisms vary, they converge. “Our work would suggest it’s not really either one of them. It’s the energy that’s derived from them, that is what’s important. What we’re doing suggests that it’s something about this final common pathway in the metabolism — the breakdown of fuels, whether they be fats or carbohydrates or protein — where this signal for hunger and satiety is generated,” he adds.

“To a large extent, how fast your stomach empties depends on how much energy is being emptied. The more energy that’s in your stomach and the greater the concentration or density of energy, the slower your stomach will empty,” Friedman notes. Aside from an initial surge, the emptying of calories, the absorption of calories, stays relatively constant during the emptying period. “Initially, the thing most people are going to be aware of is how full their stomach is. That alone can inhibit further eating. But if you fill your stomach full of low-energy food, then your stomach empties faster, and you may just want to come back and eat sooner,” he continues.

Satiety includes a psychological response. Julie Miller Jones, Ph.D., professor of nutrition, College of St. Catherine, Arden Hills, MN, uses Thanksgiving dinner, as an example. “Most everyone who leaves the table is sated and overfull,” she says. The body has had enough food, but the hand will reach for a piece of pumpkin or pecan pie. “Every signal in the body is telling you that you don’t want to eat, but the brain is telling you to eat,” she adds.

Like others in the animal kingdom, people tend to overeat especially gratifying foods. “Rats, when given rat chow will stop eating,” Jones says. “If you give them what we call the chocolate- chip-cookie diet, they will overeat.” Some experts theorize that certain foods or diets actually influence the same brain areas and chemical signals — particularly dopamine systems — that trigger drug cravings in addicts.

Satisfying ingredients

Unfortunately, there are few clearcut answers as to what might influence satiety. A volumetrics theory proposed by Barbara Rolls, a foodnutrition researcher, The Pennsylvania State University, University Park, ties volume to satiety. The strategy is that consumption of foods with a higher volume, whether through incorporation of air, water or fiber, will suppress the desire to eat again for a longer period of time. Jones, however, feels that fiber has a marginal impact. The question is: In comparing fiber derived from fresh apples or apple juice, does satiety come from the fiber or from increased chewing?

Perhaps developers can gain some clues from the satiety index developed by Australian researcher Susanna Holt. This extensive study rates foods by how much people ate to satisfy their hunger. By this measure, a croissant, 47%, is almost half as satisfying as white bread, 100%. Apples are 97% more satisfying than white bread, and oranges 102% more. In the protein category, eggs are 150%, beef is 176% and ling fish is 225%. Boiled potatoes are 323%, surpassing all.

The problem with the satiety index is that it doesn’t take into account psychological impact. A boiled potato on it’s own is rarely enticing, no matter how filling, yet it might be an integral part of a comforting pot-roast dinner. The trick then, as the homestyle pot roast illustrates, might be the marriage of two or more satisfying foods. Similarly, oatmeal, 209%, gains appeal with apples.

Improving satiety might be as simple as adding a touch of vinegar. A recent study by Elin Östman, researcher, Department of Food Technology, Engineering and Nutrition, Lund University, Sweden, found a direct relationship between increased acetic acid and satiety, with the highest satiety scores rated by subjects ingesting the highest levels of vinegar water. This study, however, used just 12 subjects.

“I don’t think we have good data,” Jones says. “Our data is all over the map. How do you measure satiety? One hour after you eat or two hours after? You will get different answers at different times. There’s so much variability in people.”

One piece of data does seem to have some merit, Jones feels. “Foods that are higher in protein tend to provide more satiety. People who are on Atkins said they felt less hungry,” she says. Because this data includes responses from people who were equally satisfied after eating egg whites, the data suggests the role of protein as opposed to fat.

This might be backed up by research by Nikhil Dhurandhar, Ph.D., executive director of The Rochester Center for Obesity Research, Rochester Hills, MI, and chair of obesity research at Detroit-based Wayne State University, Department of Nutrition & Food Science. Dhurandhar and colleagues tested overweight and obese women ages 18 to 60 to find out which breakfast was more filling: a bagel, cream cheese and yogurt (339 calories) or two eggs, toast and jelly (340 calories). Those eating eggs felt fuller after breakfast, stayed full longer than the bagel group and ate less at lunch — 568 calories versus 732 calories eaten by the bagel group. Those who ate eggs consumed a total of 1,761 calories on the test day, compared with 2,035 calories for the bagel eaters.

The researchers, who presented their findings in Las Vegas at the North American Association for the Study of Obesity’s 2004 annual scientific meeting, said the egg breakfast “induced greater satiety and reduced energy intake at lunch by 29%. Eggs have a 50% greater satiety index than breakfast cereal or bread.” They noted the need for further testing of satiety and egg breakfasts for weight-loss diets.

However, not all evidence points to protein as the cause of satiety. “Studies in France showed that, at the same protein intake, eggs had greater satiety than ham and the effect was primarily with the yolk, when they compared egg whites to egg yolks. Egg intake reduces the rate of gastric emptying and changes the secretion rates of important hormones involved in hunger/satiety responses. The effect of egg intake on the glycemic response is greater than would be predicted based on protein content alone,” says Donald J. McNamara, Ph.D., Egg Nutrition Center, Washington, D.C.

Industry answers

Dairy ingredients are a rapidly emerging area in relation to weight control and satiety. “Short-term clinical studies suggest that whey protein is effective in suppressing food,” says Peter Huth, director of regulatory and research transfer, Dairy Management, Inc.™, Rosemont, IL. “Although the mechanism of action is not well understood, some data suggest that the effect may involve the rapid digestion and absorption of whey protein amino acids (i.e., a ‘fast’ protein) into the bloodstream, as well as eliciting gastrointestinal secretions of hormones that have been shown to play an important role in satiety in humans. Additional studies are needed to verify the satiating effect of whey and the sustainability over time.”

One hypothesis contends that glycomacropeptide (GMP) stimulates secretion of cholecystokinin (CCK), a key peptide in the inhibition of gastric emptying. This acts as the basis for Twin Falls, ID-based Glanbia Nutritional’s promotion of a specific whey mineral protein that is rich in GMP and believed to increase satiety. Additionally, the composition of this whey mineral protein is based on scientific evidence that addresses weight loss through controlling fat deposition, acceleration of fat breakdown and maintenance of lean muscle.

Lipid Nutrition has focused on CCK and GLP-1 (glucagons-like peptide 1). “GLP-1 can reduce hunger and caloric intake,” explains Patrick Luchsinger, marketing manager North America, Lipid Nutrition North America, Channahon, IL. “GLP-1 is one of the gut hormones that is responsible for the ileal brake. When fatty acids reach the ileum, they will trigger specific intestinal cells to release GLP-1 into the bloodstream. These hormones then, subsequently, will influence gut transit time. Thus fats that reach the ileum will cause slowing down of transit of nutrients through the gut — ileal brake — in order to give the gut more time to absorb the nutrients.”

Lipid Nutrition can claim a patent on pine-nut oil and satiety. “We have a unique product that nobody else has so far. This extract was developed by our R&D group following the screening of several extracts in vitro on CCK and GLP-1 release,” says Luchsinger. “We have found that our product was the best CCK and GLP-1 inducer. We believe that a developer can produce a more-satisfying, filling food product with the inclusion of our product into that formulation. It lends itself to food applications such as nutritional bars, salad dressings and yogurts very well. Like most natural vegetable oils, it contains mainly fats with cis bonds and typically very little trans fats (0.2% total trans fat) may occur due to processing,” he adds.

Several animal studies have shown that consumption of inulin and/or oligofructose decreases mean daily energy intake and epidiymal fat mass. “Further investigation has shown that inulin and oligofructose influence gastrointestinal peptides that regulate food intake,” says Hilary Hursh, food and nutrition scientist, Orafti Active Food Ingredients, Malvern, PA. “The peptides, glucagonlike peptide-1, amide and peptide YY, are produced in the colon where inulin and oligofructose are fermented, but the exact mechanism for their increase has not been determined.” The health benefits of a new oligofructose by the company have been verified by numerous clinical trials.

Inulin and oligofructose replace sugar, flour and fat, or are just added to boost fiber content. “Typical usage levels reflect those needed to achieve a ‘good source’ or ‘excellent source’ of fiber — 2.5 grams fiber per serving — but may be used at higher levels,” according to Hursh.

Polydextrose might provide a good option, due to the fact that it is only 1 kcal per gram, has use in a wide variety of applications, and provides prebiotic fiber and satiating effects. “As our polydextrose exhibits many of the physiological properties as fiber, we believe the satiety mechanism may be similar and related to prolonged gastric emptying,” says Donna Brooks, product manager, Danisco Sweeteners, Ardsley, NY. “Not only is polydextrose contributing less calories than other carbohydrates it may be replacing in the food or beverage, it also reduces subsequent food intake and, therefore, reduces caloric intake in both situations. While the use of polydextrose is fairly diverse, it is most frequently used in ice cream, baked goods, nutrition bars, confections and beverages.”

Natural high-amylose-corn resistant starch has multiple benefits, including reduced glycemic response. “We also know it’s fermented and it increases short-chain fatty acids within the large intestine, which have been shown to increase the release of gut satiety peptides, such as GLP-1. In addition, the fermentation of our resistant starch also increases insulin sensitivity, which also impacts satiety,” says Rhonda Witwer, business development manager of nutrition, National Starch Food Innovation, Bridgewater, NJ.

Witwer concurs that it is difficult to get clear data. “In one study, they found decreased appetite in subjects who had eaten 30 grams of high-amylose-corn type II resistant starch, but they also felt less full.”

Unlike a lot of other fibers, resistant starch has a water-holding capacity that is similar to flour, which enables it to be used as a 1:1 substitution for flour in a variety of foods. Use levels vary depending upon the application and marketing claim. In general, natural high-amylose- corn resistant starches are used at 3% in extruded snacks, 10% in waffles and to up to 25% in baked goods such as snack crackers or cookies.

There is a difference in what the type of carbohydrate is and the effect on satiety. “Starch is essentially made up of two types of glucose chains,” Witwer explains. “Amylose is the linear type of chain that we use in our high-amylose-corn resistant starch. Amylopectin is the more-branched chains of glucose. A study compared the ratio of amylose to amylopectin in starches that were included in foods and found that the higher levels of amylose increases satiety for up to six hours after a meal, but the lower levels of amylose that had high amylopectin did not have the same effect. So, it may come down to the specific composition of different carbohydratecontaining foods and specific ingredients. We think it is very specific to what is the exact ingredient.” A separate study using a potato as a source of resistant starch did not demonstrate a satiety benefit.

“The complexity of our bodies is just astounding. There are a lot of overlapping mechanisms within the body, so getting a clear picture of what is actually happening is complicated,” says Witwer.

Scientists and developers struggle to uncover the prime mechanism and unleash a magic satiety-inducing bullet. It’s no wonder the general public may not easily define satiety. But it should lead to some interesting paths of product development in years to come.

Cindy Hazen, a 20-year veteran of the food industry, is a freelance writer based in Memphis, TN. She can be reached at [email protected].