Krieger et al actually proved this point that I’m trying to make in a study conducted in 2006 on the effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction. The objective was to use meta-regression to determine the effects of variations in protein and carbohydrate intakes on body mass and composition during energy restriction. English-language studies with a dietary intervention of > or =4200 kJ/d (1000 kcal/d), with a duration of > or =4 wk, and conducted in subjects aged > or =19 y were considered eligible for inclusion. A self-reported intake in conjunction with a biological marker of macronutrient intake was required as a minimum level of dietary control. A total of 87 studies comprising 165 intervention groups met the inclusion criteria. After control for energy intake, diets consisting of < or =35-41.4% energy from carbohydrate were associated with a 1.74 kg greater loss of body mass, a 0.69 kg greater loss of fat-free mass, a 1.29% greater loss in percentage body fat, and a 2.05 kg greater loss of fat mass than were diets with a higher percentage of energy from carbohydrate. In studies that were conducted for >12 wk, these differences increased to 6.56 kg, 1.74 kg, 3.55%, and 5.57 kg, respectively. Protein intakes of >1.05 g/kg were associated with 0.60 kg additional fat-free mass retention compared with diets with protein intakes < or =1.05 g/kg. In studies conducted for >12 wk, this difference increased to 1.21 kg. No significant effects of protein intake on loss of either body mass or fat mass were observed. Low-carbohydrate, high-protein diets favorably affect body mass and composition independent of energy intake, which in part supports the proposed metabolic advantage of these diets (2.)
Beyond the fact that increasing dietary protein will caused an increased thermic effect there by allowing you to increase calories more dramatically, we also have the simple fact that protein helps tremendously with satiety. Paddon-Jones et al looked deeper into protein, weight management, and satiety with a specific section on protein ingestion and satiety. “It is well established that under most conditions, protein is more satiating than the isoenergetic ingestion of carbohydrate or fat. This suggests that a modest increase in protein, at the expense of the other macronutrients, may promote satiety and facilitate weight loss through reduced energy consumption. The increased satiety from protein has been observed in a single meal and over 24 h. In one short-term study, satiety and metabolic rate were examined over a 24-h period in a respiration chamber. Throughout the day, satiety was greater in the high-protein group (protein/carbohydrate/fat: 30/60/10% energy) compared with the high-fat group (protein/carbohydrate/fat: 10/30/60% energy). Importantly, this effect was noted during postprandial periods as well as during meals. It must be noted, however, that in this instance greater satiety was observed in response to a 3-fold greater protein load, a condition unlikely to represent a normal dietary intake for most individuals.
Despite some evidence that habitual exposure to a higher-protein diet may diminish its effect on satiety, others have suggested that the greater satiating effects of a higher-protein diet are relatively long lasting. In a 16-week study, subjects consuming a high-protein (34%)/lower-fat (29%) diet reported greater postmeal satiety than subjects consuming a standard protein (18%)/higher-fat (45%) diet. In some cases, the generally higher satiating effects of protein are not evident. Acutely, carbohydrate is very satiating, yet protein usually has a greater prolonged satiating effect. However, under normal conditions, fiber intake, the timing of the assessment, the food form (ie, solid versus liquid), or coingestion of other macronutrients may ultimately influence reported satiety. There is some suggestion that different protein sources differentially affect satiety. Specifically, it has been shown that ingestion of animal (pork) protein resulted in a 2% higher energy expenditure than ingestion of a plant-based protein (soy). Further, there is evidence that more rapid gastric emptying and a postprandial increase in plasma amino acid concentrations after ingestion of specific proteins (eg, whey versus casein) may increase satiety because of a greater stimulatory effect on gastrointestinal hormones such as cholecystokinin and glucagon-like peptide-1. For example, casein-derived peptides (casomorphins) reduce gastrointestinal motility, resulting in lower postprandial plasma amino acid concentrations, which in turn blunt the satiating effect of higher plasma amino acid concentrations. In comparison, caseinomacropeptide, a glycosylated peptide comprising 15–20% of whey products, stimulates cholecystokinin production and has been shown to increase satiety in some, but not all, studies. However, despite the suggestion of acute or transient benefits attributable to specific proteins, any such effect may be masked by the concomitant ingestion of a mixture of proteins and other macronutrients in a normal mixed diet.
Ghrelin has been shown to stimulate appetite and promote food intake and may facilitate weight gain. Plasma ghrelin concentrations follow a cyclical pattern, increasing before meals and decreasing shortly thereafter. The postprandial reduction is influenced by the relative proportion of macronutrients in a meal, with a greater decrease after protein and carbohydrate ingestion than after fat ingestion. However, increased satiety and reduced appetite associated with an increased dietary protein intake may not be mediated by ghrelin homeostasis (3.)
- Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. Carol S. Johnston, Carol S. Day, Pamela D. Swan. J Am Coll Nutr. 2002 (https://www.ncbi.nlm.nih.gov/pubmed/11838888)
- Effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction: a meta-regression. James W. Krieger, Harry S. Sitren, Michael J. Daniels, Bobbi Langkamp-Henken. Am J Clin Nutr. 2006 (https://www.ncbi.nlm.nih.gov/pubmed/16469983)
- Protein, weight management, and satiety. Douglas Paddon-Jones, Eric Westman, Richard D. Mattes, Robert R. Wolfe, Arne Astrup, Margriet Westerterp-Plantenga. Am J Clin Nutr. 2008 (https://www.ncbi.nlm.nih.gov/pubmed/18469287)
- Indicator Amino Acid-Derived Estimate of Dietary Protein Requirement for Male Bodybuilders on a Nontraining Day Is Several-Fold Greater than the Current Recommended Dietary Allowance. Bandegan A, Courtney-Martin G, Rafii M, Pencharz PB, Lemon PW. J Nutr. 2017. (https://www.ncbi.nlm.nih.gov/pubmed/28179492)
- Effect of a high-protein breakfast on the postprandial ghrelin response. Wendy A. M. Blom, Anne Lluch, Annette Stafleu, Sophie Vinoy, Jens J. Holst, Gertjan Schaafsma, Henk F. J. Hendriks. Am J Clin Nutr. 2006 (https://www.ncbi.nlm.nih.gov/pubmed/16469977)
- Ghrelin and glucagon-like peptide 1 concentrations, 24-h satiety, and energy and substrate metabolism during a high-protein diet and measured in a respiration chamber. Manuela P. G. M. Lejeune, Klaas R. Westerterp, Tanja C. M. Adam, Natalie D. Luscombe-Marsh, Margriet S. Westerterp-Plantenga. Am J Clin Nutr. 2006 (https://www.ncbi.nlm.nih.gov/pubmed/16400055)
- Higher protein intake preserves lean mass and satiety with weight loss in pre-obese and obese women. Heather J. Leidy, Nadine S. Carnell, Richard D. Mattes, Wayne W. Campbell. Obesity (Silver Spring) 2007 (https://www.ncbi.nlm.nih.gov/pubmed/17299116)
- The satiating effect of dietary protein is unrelated to postprandial ghrelin secretion. Lisa J. Moran, Natalie D. Luscombe-Marsh, Manny Noakes, Gary A. Wittert, Jennifer B. Keogh, Peter M. Clifton. J Clin Endocrinol Metab. 2005 (https://www.ncbi.nlm.nih.gov/pubmed/16014402)
- Effects of Meals High in Carbohydrate, Protein, and Fat on Ghrelin and Peptide YY Secretion in Prepubertal Children. Lomenick, J. P., Melguizo, M. S., Mitchell, S. L., Summar, M. L., & Anderson, J. W. (2009). The Journal of Clinical Endocrinology and Metabolism. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2775646/)
- Ghrelin enhances appetite and increases food intake in humans. A. M. Wren, L. J. Seal, M. A. Cohen, A. E. Brynes, G. S. Frost, K. G. Murphy, W. S. Dhillo, M. A. Ghatei, S. R. Bloom. J Clin Endocrinol Metab. 2001 (https://www.ncbi.nlm.nih.gov/pubmed/11739476)