Dietary Protein in Body Weight Regulation

The type of protein matters

Professor Margriet Westerterp-Plantenga, staff member in the Department of Human Biology at Maastricht University, and project leader within the Top Institute Food and Nutrition (TIFN), is an acknowledged scientist in the field of weight management.

Since losing weight can be accomplished by almost any diet, Westerterp-Plantenga and her colleagues have focused their attention on the prevention of weight (re)gain in order to prevent the so-called “yo-yo effect.”

For example, a recent project, “The Role of Dietary Protein in Satiety and Weight Management” was designed to detail the protein-induced decrease in food intake and the increase in energy expenditure effects.

Quantity and type of protein are important features of diet

Figure 1a. Satiety ratings after consumption of a breakfast custard with one single protein, in a concentration of 10 percentage of energy. Satiety was significantly higher after breakfasts containing gelatin, gelatin plus tryptophan, or alpha-lactalbumin. After Veldhorst et al. Clin. Nutr. 2009, 28:147-155, 2009.

Figure 1b. Energy intake at lunch, at a predetermined moment in time, i.e., three hours after a breakfast custard with one single protein, in a concentration of 10 percentage of energy. Breakfasts contained from left to right: casein, soy, whey, whey minus glyco-macro-peptide, alpha-lactalbumin, gelatin, gelatin plus tryptophan. Energy intake was significantly less after breakfasts containing gelatin, gelatin plus tryptophan, or alpha-lactalbumine than after casein, soy, whey, or whey minus glyco-macro-peptide. After Veldhorst et al. Clin. Nutr. 2009, 28:147-155, 2009.

High protein diets are a popular strategy for weight loss and weight maintenance. Westerterp-Plantenga and her co-workers have developed several research lines into protein-modulated mechanisms affecting body weight. Recent results are briefly addressed here and clearly indicate that the type and amount of protein may be important features of specific diets.

A breakfast with alpha-lactalbumin, gelatin, or gelatin with added tryptophan was approximately 40% more satiating compared to a breakfast containing a equivalent amount of protein calories coming from casein, soy, whey or whey without glycomacropeptide (GMP) as a protein source. Moreover, a breakfast with alpha-lactalbumin, gelatin or gelatin with added tryptophan showed a related reduction of approximately 20% of energy intake at a subsequent lunch (Clin Nutr. 2009 Apr;28(2):147-155). Thus, significant differences in energy intake during a test meal, and even beyond, can be demonstrated.

Studies in which whey (with or without GMP), soy protein or casein were assessed for their satiating effects, (satiety) hormones, plasma amino acid responses and energy intake during a subsequent lunch were undertaken, as well. These studies revealed, for example, that GMP as a whey fraction reduced energy intake coinciding with increased concentrations of certain amino acids, irrespective of the concentration of whey protein (Appetite. 2009 Apr;52(2):388-395). A high soy protein breakfast turned out to be more satiating than a normal soy protein breakfast related to taurine and insuline levels (Eur J Nutr. 2009 Mar;48(2):92-100). Another study demonstrated that a breakfast with 25% of its energy from casein was rated more satiating than a breakfast with 10% of its energy from casein at 3 and 4 hours after breakfast, coinciding with elevated concentrations of plasma amino acids (Br J Nutr. 2009 Feb;101(2):295-303). However, neither a high casein nor a high soy protein breakfast reduced subsequent energy intake at lunchtime. Hence, in these settings, some proteins may affect satiation (acute satiety) without affecting satiety towards a subsequent meal. Amino acids and metabolites may be responsible mediators explaining this acute effect.

In another, single-protein diet study, with either 25% or 10% of energy from protein, the effect of casein with respect to energy expenditure, substrate balance, and appetite profile was measured over 24 hours, during a 36-hour respiration chamber stay. The 25En% casein diet resulted in a 2.6% higher 24-hour total energy expenditure and a higher sleeping metabolic rate than did the 10En% casein diet. With the 25En% casein diet, compared with the 10En% casein diet, the subjects were in positive protein balance and negative fat balance, while positive carbohydrate balances were not significantly different between the diets.

Figure 2. Whole-body 14 m3 respiration chambers for measuring energy balance, substrate balance and energy expenditure. Actual measurements in the respiration chamber consisted of substrate oxidation and energy expenditure for 36 hours, appetite profiles with visual analog scales from 9:00-22:30h. After Hochstenbach-Waelen et al., Am J Clin Nutr. 2009 Mar; 89(3):831-838.

Furthermore, dietary protein is not only capable of maintaining or reducing weight. A high versus normal protein diet consumed over 3 months in energy balance, without changes in physical activity, appears to increase stimulated fat-oxidation, and increases fat-free mass at the cost of fat mass, thereby creating a favorable effect to body composition, as well (Int J Obes Relat Metab Disord. 2004 Jan;28(1):57-64).

Figure 3. Dietary intervention in respiration chamber: Test diets: 25En% casein (25/20/55En% P/F/C) or 10En% casein diet (10/35/55En% P/F/C) with casein as the only protein source, mainly given as a vanilla custard. Energy intake for energy balance was calculated as Basal Metabolic Rate multiplied by an activity factor of 1.35. 9:00 AM breakfast (20En% of daily energy intake), 13:45 lunch PM (40En%), 19:30 dinner PM(40En%). Energy expenditure at 25En% casein vs 10En% casein, with line of identity. After Hochstenbach-Waelen et al., Am J Clin Nutr. 2009 Mar; 89(3):831-838.

Figure 4. Dietary intervention in respiration chamber: Substrate balances for protein, fat and carbohydrate. Closed bars: 25En% of casein; open bars 10En% of casein. Protein balance is significantly higher and fat balance is significantly lower after 25En% of casein than after 10En% of casein. After Hochstenbach-Waelen et al., Am J Clin Nutr. 2009 Mar; 89(3):831-838.	Figure 5. Dietary intervention in respiration chamber: Visual analog scores of hunger throughout the day. Time point 0 minutes is 8:00 AM: baseline score before breakfast. After Hochstenbach-Waelen et al., Am J Clin Nutr. 2009 Mar; 89(3):831-838.

Other research lines relating to weight management

Many other research lines are also being explored by Westerterp-Plantenga. Two examples are provided here as an illustration of this multifaceted research program. Several bioactive ingredients, for example, have been studied in relation to satiety. The acute effects of a lunch containing the spice capsaicin were tested. No effect on satiety, energy expenditure or the hormone PYY was seen. However, capsaicin increased the gut derived hormone or GLP-1 and tended to decrease ghrelin (Eur J Nutr. 2009 Feb 24 (Epub ahead of print)). In another study, CH-19 sweet pepper and a combination of capsaicin and green tea showed an energy intake reducing effect in positive energy balance. These bioactive ingredients may, therefore, support weight loss periods by relatively sustaining satiety and suppressing hunger (Clin. Nutr. 2009 Apr 2 (Epub ahead of print)). As a final example, effects of stress on food choice and intake, related to decreased food-related reward activation in the brain, are mentioned here. It could be concluded that reward signaling and reward sensitivity are lower under stress, resulting in a relatively larger food intake in the absence of hunger (Abstracts by JM Born et al., Obesity Facts 2009, 2:17 and SGT Lemmens et al., Obesity Facts 2009, 2:141).

Contact Details
M.Westerterp@hb.unimaas.nl

About the Top Institute Food and Nutrition (TIFN)

The Top Institute Food and Nutrition (TIFN) is a public/private partnership carrying out strategic fundamental research of commercial relevance. At TIFN, the research is flexibly organized in themes and projects, which are all aimed at the development of innovative products and technologies that respond to consumer demands for safe, tasty and healthy food. Three interrelated programs: “Nutrition and Health,” “Sensory and Structure” and “Bioingredients and Functionality” have been established in which the research is jointly decided upon and guided by the industry and research partners. Over 46 patents have been filed and innovative products and knowledge have been introduced. The results achieved and experiences gained underscore the ambition to increase the size and scope of the research portfolio and attract new partners from the food and nutrition industry.
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