Protein and Satiety

By Marie Spano, M.S., R.D., C.S.C.S.
Contributing Editor

Its no secret that America is on a mission to lose weight. According to 2005 to 2006 statistics from Centers for Disease Control and Prevention, Atlanta, more than one-third of American adults are obese. Although the bottom line often boils down to the calorie-balance equationeating too many calories and not getting enough physical activitythere are certain macronutrients and food components that are more filling than others, satiating the appetite so people eat less throughout the day.

The issue of weight management is a significant concern for many people, so controlling hunger can be an appealing message to consumers, says Laura Gottschalk, vice president, U.S. manufacturing and ingredient marketing, Dairy Management Inc. (DMI), Rosemont, IL.

Though the low-carb, high-protein diet craze has come and gone, protein still stands out as a key macronutrient in the war against weight loss. While the value of protein to promote satiety is not a new discovery, it is receiving much more interest as consumers, governments and researchers seek solutions to the growing global crisis around obesity, says Michele Fite, vice president, global strategy and marketing and specialty business, Solae, St. Louis. High-quality proteine.g., milk, eggs, lean meat and soy proteinas research supports, is playing a key role in new food-product development to help deliver these solutions. We see a strong demand for soy protein to be incorporated into more of a variety of food applications, including bars, nutritional drinks, cereals, breads, and bakery products.

The power of protein

Both animal and human studies show that consuming protein, as compared to carbohydrate and fat, promotes stronger feelings of satiety and suppresses food intake at the next meal. In humans, visual analogue scales (which use a scale to measure how hungry a person is) and food intake are often used to measure satiety. In addition, changes in hormone levels that affect appetite can provide a closer look at how the three macronutrients impact satiety and hunger. Cholecystokinin (CCK) is an intestinal hormone that is released after a meal and signals satiety. Increased levels of peptide YY (PYY) signal satiety, and ghrelin levels increase when we are hungry. In addition to altering our feelings of satiety, protein-rich meals stimulate CCK and inhibit ghrelin, providing a biological explanation for how protein works to influence satiety.

The type and total amount of protein consumed may play a key role in satiety. However, from the current body of literature, it is difficult to ascertain how much protein should be consumed to enhance satiety. And, the dose requirement may depend in part on body weight and the time until the next meal.

Pick a protein

What types of protein are best for enhancing satiety? Consuming a diet high in protein, especially milk-based proteins, has been shown to affect satiety, says Jose Antonio, Ph.D., F.I.S.S.N, CEO, International Society of Sports Nutrition, Woodland Park, CO. In fact, it will help with appetite regulation.

Matt Pikosky, R.D., director of research transfer, National Dairy Council, Rosemont, IL, says whey protein added to foods and beverages can help increase daily protein intake to achieve a higher-protein diet, which can help promote a feeling of fullness. Milk proteins might be preferential because they are high in whey and casein, both of which contain glycomacropeptide, a peptide that stimulates CCK. In a study comparing whey, casein and soy consumed at breakfast in young, healthy subjects, whey decreased hunger to a greater extent as measured by a visual analogue scale, but it didnt decrease energy consumed at the next meal (Physiology & Behavior, 2009; 96(4-5):675-82). Whey consumption also led to greater increases in amino concentrations (leucine, lysine, tryptophan, isoleucine and threonine) and hormone responses (insulin and glucagon-like peptide 1).

Soy protein is also beneficial for enhancing satiety. Food companies are discovering that soy protein can add functionality to products, notes Mian Riaz, Ph.D., director, Food Protein R&D Center, Texas A&M University, College Station, and consultant to the United Soybean Board, Chesterfield, MO. Some enhanced-trait soybeans now contain very little lipoxigenase enzymes, which are responsible for beany flavor. As a result, manufacturers are able to use soybean ingredients with very neutral flavor in their food products in order to reap the benefits of proteins satiety effect and all the benefits of heart-healthy soy protein in particular.

In addition to protein type, the time of day protein is consumed may also matter for those on a calorie-restricted diet. In one study, during calorie restriction, eating more protein at breakfast (0.6 grams protein per kg bodyweight) led to greater meal-related satiety and overall fullness than eating more protein at lunch or dinner (British Journal of Nutrition, 2009; 101(6):798-803).

Marie Spano, M.S., R.D., C.S.C.S., is a nutrition communications expert whose work has appeared in popular press magazines, e-zines and nutrition-industry trade publications. She has been an expert guest on NBC, ABC and CBS affiliates on the East Coast. For more information, visit mariespano.com.