Protein is a well-known appetite suppressant – it works in a number of ways.
A qualiity protein intake boosts metabolism by preserving lean muscle mass, balances blood-glucose levels, reduces appetite and affects several weight-regulating hormones. Fat-loss associated with a high protein diet includes subcutaneous and also metabolically-active visceral fat.
Protein is an important factor in a weight-loss diet. Protein’s powerful hunger-reducing effects may be the most important factor in weight-loss. It also regulates the function of weight-regulating hormones.[1,2]
The hypothalamus regulates and processes a number of different types of information including appetite-regulating chemicals. For example, higher levels of protein increase the satiety hormones glucagon-like peptide 1 (GLP-1), peptide YY and cholecystokinin while reducing levels of the hunger-hormone ghrelin.[3-6]
Digesting and metabolising protein also burns calories which is called the thermic effect of food (TEF). Protein has a TEF of 20-30%, compared to carbohydrates (5-10%) and fat (0-3%). Thus, if protein has a TEF of 30%, out of 100 calories only 70 are used while 30 are burnt off as heat.
Consuming 30% of calories from protein may also mean that fewer calories are consumed. In a study published in the American Journal of Clinical Nutrition, participants consumed an average of 441 fewer calories per day when their diet was comprised of 30% protein compared with when they followed a diet comprising 10% protein. Other research has shown that a protein-rich diet boosts metabolism and increases the number of calories burned by about 80 to 100 per day.[9-11]
On a weight-reducing diet, it is essential to consume sufficient protein to help reduce fat mass, retain muscle mass and maintain a healthy metabolism. On a high-protein diet, more calories are burned throughout the day and also during sleep.
Muscle-loss can be an unwanted side effect of weight-loss since this can reduce metabolic rate. A high-protein diet can help to minimise muscle-loss and maintain a higher metabolic rate while losing body fat – both subcutaneous and visceral. Consumption of protein can reduce muscle loss, thus helping to retain a higher metabolic rate as you lose body fat.[13-16]
Resistance or strength training has also been shown to reduce muscle-loss and metabolic slowdown during a weight-loss program. Any weight-reducing diet must be used in conjunction with restricted calorie intake and regular exercise. Protein provides a similar number of calories to carbohydrates and overconsumption of calories from any source can negate the calorie deficit caused by the increased protein intake.
Most studies that have examined the effect of protein in weight-loss have expressed intake as a total daily percentage; an intake of 30% intake of protein of calories seems to be effective for weight-loss. A total of 30% of calories amounts to 150 grams of protein on a 2000 calorie diet. However, a range of 25-35% seems to be useful, too.
Meat, dairy, eggs and animal protein alternatives such as legumes and lentils, seeds and nuts are good dietary sources of protein. A dietary protein supplement incorporating protein from whey, casein, egg, or soy is a helpful option if an individual is struggling to consume enough protein.
Brown rice protein powder is an alternative to traditional protein powders and is compatible with vegan, gluten-free and low-allergen diets. Brown rice protein powder is especially high in cysteine, a sulphur-containing amino acid needed for glutamine synthesis and methionine, which plays an important role in the synthesis of other proteins, such as carnitine which helps convert fats to energy.
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- Astrup A, Raben A, Geiker A. The role of higher protein diets in weight control and obesity-related comorbidities. Int J Obes (Lond). 2015 May; 39(5):721–726 [Full Text]
- Lejeune MP, Westerterp KR, Adam TC, et al. 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. Am J Clin Nutr. 2006 Jan; 83(1):89-94 [Full Text]
- Batterham R, Heffron H, Kapoor S, et al. Critical role for peptide YY in protein-mediated satiation and body-weight regulation. Cell Metab. 2006 Sep 4(3):223–233 [Full Text]
- Jefferson P, Lomenick MS, Melguizo SL, et al. Effects of Meals High in Carbohydrate, Protein, and Fat on Ghrelin and Peptide YY Secretion in Prepubertal Children. J Clin Endocrinol Metab. 2009 Nov; 94(11):4463-4471 [Full Text]
- Blom WA, Lluch A, Stafleu A, et al. Effect of a high-protein breakfast on the postprandial ghrelin response. Am J Clin Nutr. 2006 Feb; 83(2):211-220 [Full Text]
- Westerterp, K. Diet induced thermogenesis. Nutr Metab (Lond) 2004; 1: 5 [Full Text]
- Weigle DS, Breen PA, Matthys CC, et al. A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. Am J Clin Nutr. 2005 Jul; 82(1):41-48 [Full Text]
- Johnston CS, Day CS, Swan PD. Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J Am Coll Nutr. 2002 Feb; 21(1):55-61 [Abstract]
- Veldhorst MA, Westerterp-Plantenga MS, Westerterp KR. Gluconeogenesis and energy expenditure after a high-protein, carbohydrate-free diet. Am J Clin Nutr. 2009 Sep; 90(3):519-526 [Full Text]
- Veldhorst MA, Westerterp KR, van Vught AJ, Westerterp-Plantenga MS. Presence or absence of carbohydrates and the proportion of fat in a high-protein diet affect appetite suppression but not energy expenditure in normal-weight human subjects fed in energy balance. Br J Nutr. 2010 Nov; 104(9):1395-405 [Abstract]
- Bray G, Redman L, de Jonge L, et al. Effect of protein overfeeding on energy expenditure measured in a metabolic chamber. The American Journal of Clinical Nutrition. Am J Clin Nutr 2015 Mar; 101(3):496-505 [Abstract]
- Mettler S, Mitchell N, Tipton KD. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010 Feb; 42(2):326-337 [Abstract]
- Kim JE, Sands L, Slebodnik M, et al. Effects of high-protein weight loss diets on fat-free mass changes in older adults: a systematic review. FASEB J 2014 Apr; 28(1):supp371.5 [Abstract]
- Layman DK, Evans E, Baum JI, et al. Dietary protein and exercise have additive effects on body composition during weight loss in adult women. J Nutr. 2005 Aug; 135(8):1903-10 [Full Text]
- Layman DK, Boileau RA, Erickson DJ, et al. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr. 2003 Feb; 133(2):411-417 [Full Text]