A randomized trial to manipulate the quality instead of quantity of dietary proteins to influence the markers of satiety☆,☆☆,★,
Introduction
Weight loss is an effective measure in prevention and management of diabetes (Hamman et al., 2006, Wing, 2010), and caloric restriction is the cornerstone of most weight loss approaches. However, long-term compliance with a reduced-energy diet is challenging (Holt, Brand-Miller, & Stitt, 2001). Therefore, additional supportive strategies such as nutritional approaches that enhance satiety are needed to increase compliance with weight loss diets. Foods differ in their ability to reduce hunger and increase satiety (Holt, Miller, Petocz, & Farmakalidis, 1995). Protein quantity is a factor positively correlated with satiety index score (SIS) of different test foods (Holt et al., 1995). This property of proteins has been exploited for weight loss. Clinical trials have shown that high protein diets result in greater short-term weight loss or fat loss (Larosa et al., 1980, Layman, Boileau, Erickson, et al., 2003, Westman et al., 2002), but the results are not maintained over time (Foster et al., 2003, Nordmann et al., 2006, Sacks et al., 2009, Stern et al., 2004). Thus, the role of increasing protein quantity to reduce energy intake has been questioned (Blatt, Roe, & Rolls, 2011). In addition, concerns about the potential adverse side effects of high protein diets have been expressed (Anderson et al., 2000, Reddy et al., 2002). An alternative approach may be to focus on protein quality, instead of the quantity. The Protein Digestibility Corrected Amino Acid Score (PDCAAS) indicates the amino acid composition of the protein and thus reflects protein quality (Layman, 2004). Consuming greater amounts of high quality protein, particularly at breakfast, has been recommended for a favorable body composition change during weight loss (Layman, 2004). Also, breakfast foods with high SIS induce a greater feeling of fullness compared to those with lower SIS (Holt et al., 2001) and are also negatively correlated with energy intake at lunch (Holt et al., 2001). Therefore, we determined if the satiating effect of proteins could be harnessed by increasing the protein quality without increasing protein quantity in a test breakfast.
This study tested the hypothesis that an EB will induce greater satiety than a ready-to-eat CB that has lower protein quality but similar energy density (ED) and macronutrient composition. We opted to compare the two breakfasts for the following reasons: eggs are a common breakfast food with superior protein quality, have a 50% greater SIS than ready-to-eat (RTE) cereal (Holt et al., 1995) – another commonly consumed breakfast. Eggs and cereals have a PDCAAS of 100 and 42, respectively (Schaafsma, 2000). In addition, the two foods have a differing content of the branched chain amino acid (BCAA) leucine, an important contributor to protein quality (Layman and Walker, 2006, Norton et al., 2012). Since the EB had a greater PDCAAS and more than three times the amount of leucine than the CB, the EB was considered to be a relatively higher quality protein breakfast. We reasoned that if a test meal higher in protein quality enhances objective and subjective measures of satiety, then future weight loss trials may manipulate protein quality instead of quantity, which has not been tested in long term weight loss trials.
Section snippets
Ethics statement
This study was approved by the institutional review board at the Pennington Biomedical Research Center (PBRC; IRB#10010). Written informed consent was obtained from the subjects prior to the initiation of study procedures. The Study was conducted at PBRC, in an outpatient setting.
This trial was registered with Clinicaltrials.Gov (http://www.clinicaltrials.gov/) #NCT01413217 (http://www.clinicaltrials.gov/ct2/show/NCT01413217?term=eggs+Pennington&rank=2). Subjects were recruited starting July
Results
A total of 20 subjects completed the study [female (75%), African American (70%), mean age 40.7 ± 14.1 years, and mean BMI 37.5 ± 4.1 kg/m2. The two groups had similar age, body weight and BMI (Table 2)].
Discussion
Although reducing excess weight by inducing a negative energy balance is an excellent adjunct to preventing or managing diabetes, adherence to a reduced calorie diet can be difficult to maintain over time. Therefore, dietary strategies that decrease hunger and increase satiety may promote compliance and enhance weight loss (Rolls and Bell, 2000, Vander Wal et al., 2008). The higher SIS of proteins presents the opportunity to manipulate their quantity in the diet to induce satiety. Diets with
Acknowledgments
Funding: Funded by a peer-reviewed grant from the American Egg Board/Egg Nutrition Center. The funding agency had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
We gratefully acknowledge the assistance of Ms. Kimberly Phillip in clinically coordinating the study, that of Ms. Renee Puyau for carefully developing the matching breakfasts, and that of Ms. Mary Beth Burnett in administrative assistance.
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Cited by (0)
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Sources of support: This study was funded by a grant received from the American Egg Board.
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Clinical trial registry: NCT01413217 (http://clinicaltrials.gov/ct2/show/NCT01413217).
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This study was presented at the European Congress on Obesity as an oral presentation, in May 2012, in Lyon, France.
Conflict of interest: The authors declare that no competing interests exist.