May 26, 2009
by Editorial Staff
Amid the variety of discussions about health, nutrition and the current obesity problem in the United States, a few truths stand as universal. One is the fact calories count. Choosing the right kinds of foods to eat is obviously important, but weight management still comes down to calories consumed versus calories expended.
For this reason, the concept of satiety is one that has gotten more attention in recent years. The simplest definitions of satiety describe it as the physical sensation of being full.
For nearly everyone, satiety is the cue to stop eating. The trouble is some foods provide a much higher number of calories than others before they satisfy enough to get consumers to put down the fork. And for too many people that leads to an overweight condition or obesity.
From a physiological perspective, satiety is well understood. Receptors in the digestive tract send certain hormones to the hypothalamus section of the brain. The hormones send signals to other systems and cause a drop in appetite. In addition, there are psychological, environmental and cultural conditions that may influence the process as well.
Of course the satiety process doesn’t operate in a vacuum. There are numerous factors, including the metabolism, activity level and general health of the individual, as well as the make-up of overall diet that play a role in nutrition and weight management. But satiety, an aspect of nutrition that has sometimes been overlooked or not very well understood, has become a key consideration in the discussion, of nutrition, weight loss and weight management.
Most recently, studies have indicated a diet rich in proteins may be more effective than others for achieving satiety.
"The impact of dietary protein on satiety is an area that has recently gained a considerable amount of attention in both the scientific literature and lay press," said Matt Pikosky, director of research transfer for Dairy Management Inc. (D.M.I.) "Studies have shown that protein intake exerts a more powerful effect on satiety than either carbohydrate or fat. As such, higher protein diets, through their impact on satiety, may play an important role in weight management. Considering the rates of obesity continue to rise in the U.S., satiety, and its potential impact on weight management, is timely and of considerable importance."
For those in the dairy industry this is good news. Standard dairy products are good sources of protein and most are readily available in low-fat and/or fat-free formulations. In addition, dairy ingredientsrepresent a significant segment of the dairy processing industry. The ingredients consist of proteins that are used in a variety of prepared foods that include everything from toaster treats and confectionery bars to energy drinks.
While the dairy industry always has positioned milk and other dairy products as wholesome good-for-you foods, that message has been honed over the years, and currently is focused more tightly on nutrient density, a notion which is at least related to (and perhaps inextricable from) satiety. And while dairy ingredients themselves are a great source of protein for formulating other foods, the combination of dairy protein and fiber seems to provide so much satiety and nutritional benefits that fiber is now a key added ingredient in many specialty dairy-based products.
Surveys and clinical studies
When not hungry, consumers are less tempted to reach for unhealthy/unwanted snacks. According to research by Mintel International, Chicago, 29% of American adults choose functional foods to avoid eating empty calories; 28% select functional foods for weight maintenance reasons; and 45% of U.S. adults reach for functional foods to make up for their less-than-healthy eating habits. Further, Mintel research showed that 65% of U.S. adults who purchased functional foods in the prior three months did so for weight maintenance reasons.
There has been a significant amount of research published in the past few years related to protein, satiety and weight management. Studies have examined the impact of a specific meal or preload on short-term satiety and energy intake as well as overall diets higher in protein on satiety, energy intake and weight management.
"Several recent reviews have concluded that protein is more satiating than carbohydrate and fat," Mr. Pikosky said. "And they show that higher protein diets can play a role in weight management by increasing satiety and, when combined with a reduced calorie diet, improve the quality of weight loss by increasing the loss of body fat and/or preserving lean muscle."
Mr. Pikosky pointed to three review papers that were completed and published this past year, including "Protein, weight management and satiety," American Journal of Clinical Nutrition, May 2008; "Energy expenditure, satiety, and plasma ghrelin, glucagon-like peptide and peptide tyrosine-tyrosine concentrations following a single high protein lunch," The Journal of Nutrition, April 2008; and "Protein-induced satiety: Effects and mechanisms of different proteins," Physiology & Behavior, January 2008.
The implications for dairy are positive, Mr. Pikosky said.
"Low-fat and fat-free dairy products as well as products containing whey protein are a great option for consumers to include into their daily diet to help boost their overall protein intake and achieve a higher protein diet," he said.
Research published in 2004 by G. Harvey Anderson and Shannon E. Moore at the Department of Nutritional Sciences at the University of Toronto and titled "Dietary proteins in the regulation of food intake and body weight in humans," also indicated protein is a great source for satiety. More importantly for dairy, the authors stated dairy proteins are higher in the branched-chain amino acids (especially leucine), compared with meat or plant proteins. This has been proposed to be of benefit to food intake regulation and the maintenance of lean body mass on energy reduced diets, according to the review.
Ingredients that increase satiety
In 2004, Dr. Barbara Rolls, a researcher with a Ph.D in physiology, published a diet book on satiety. The Volumetrics Eating Plan didn’t receive the same level of media attention as its contemporary, Dr. Atkins’ New Diet Revolution Diet Plan, but Volumetrics has had some staying power and it has helped fuel the current interest in satiety.
Ms. Rolls emphasized foods with high water content, noting that in studies they tended to contribute most significantly to satiation. But what comes after water, Ms. Rolls said, is fiber, especially soluble fiber, like that found in oats.
For dairy processors, adding soluble fiber to products such as dairy drinks, yogurt, and even cottage cheese, has become a way to offer a double-dose of satisfaction, and nutrient density.
Among the best-equipped ingredients for making that happen is oat bran concentrate, a natural, highly concentrated oat soluble fiber containing 54% beta-glucan, up to 18 times more beta-glucan than rolled oats. One ingredient supplier offers a mixture of oat brand concentrate and palm oil.
Among the most widely used ingredients in this arena are inulin and oligofructose. Inulin is a term applied to a heterogeneous blend of fructose polymers found widely distributed in nature as plant storage carbohydrates. Oligofructose is a sub-group of inulin, consisting of polymers with a lower degree of polymerization. Because they are not digested in the upper gastrointestinal tract these products have a reduced caloric value.
The fermentation of inulin and oligofructose in the colon stimulates the growth of beneficial bifidobacteria, and the process has been shown to modulate production of, and blood levels of, colonic hormones involved in appetite regulation. In addition, select varieties increase secretion of hormones that stimulate satiety and reduce hunger.
Other types of ingredients that may aid in satiety include natural resistant starch (an insoluble fiber), digestion resistant maltodextrin, polydextrose, and fruit extracts that are similar to the citric acid.
Put it on a scale
As was stated earlier, weight management boils down to calories consumed versus calories expended. But finding time to burn calories may be just as challenging to consumers as being careful about what they eat.
By combining satiating components like protein and fiber, and offering packaging products in the right portion size, dairy processors may offer the best of both worlds — foods that curb hunger without adding pounds.
In fact a few years ago, a small entrepreneurial company from California created a dairy-based product line anchored to the satiety concept. Earlier this year the company went out of business, but that may have had more to do with the underlying economy than with the underlying validity of its products.
LifeFull Foods’ Satiety Smoothies were made from water, whey protein, and ingredients including inulin. Weighing in at just 90 calories, the flavored smoothies offered 5 grams of protein and 5 grams of fiber, in an 8.25-oz bottle
The scientific community has yet to adopt a true satiety scale, but LifeFull used a simple calculus to help market the satiating qualities of its products. The company used the combined weight of its protein and fiber content, divided by its calories as a "satiety scale." The beverages tipped that scale advantageously for hungry yet calorie-conscious consumers. A Satiety Smoothie weighed in at 12-13 satiety units, while an energy bar scored a 7 on the scale, with an apple or a lowfat flavored yogurt coming in around 3. A Snickers bar, thanks to its high calorie count, really didn’t satisfy, scoring only a 2.