Weight Loss Practices: Does increasing protein intake yield better

Weight Loss Practices: Does increasing protein intake yield better results?
The Acceptable Macronutrient Distribution Range (AMDR) is “the range of intake for a
particular energy source that is associated with reduced risk of chronic disease while providing
intakes of essential nutrients”1. These ranges, as defined by the Institute of Medicine, are as
follows for adults: 45-65% of calories as carbohydrate, 20-35% as fat, and 10-35% as protein (or
0.8 g protein/kg/day). Recent research shows that a weight loss diet with moderate protein levels
(towards the higher end of the AMDR) reduces fat mass while preserving lean muscle, thus,
improving body composition. Usually, weight loss is accompanied by a decrease in lean body
mass (LBM) and thus, resting metabolic rate (RMR). Loss of LBM is not desirable at any age,
but especially in older adults as skeletal muscle and RMR already decline with age. A higher
protein weight loss diet is purported to reduce the loss of LBM for a number of reasons,
including effects on satiety and muscle metabolism. This essay will briefly explore the potential
advantages of a moderate protein diet as well as issues of concern.
Macronutrient Composition and Weight Loss
During weight loss or maintenance, weight and body composition changes may differ depending
on the macronutrient composition of the diet plan. Subjects on an energy restricted diet
composed of 40% carbohydrate, 30% fat, and 30% protein had similar weight loss, but lost 22%
more fat mass, when compared to those on an energy restricted diet with a macronutrient
distribution of 55% carbohydrate, 30% fat, and 15% protein2. Although weight loss was not
significantly different between groups, the higher protein group showed a significantly greater
improvement in body composition. Similarly, another study showed that an energy restricted
diet composed of approximately 30% protein enhanced fat loss by 1-2 kg compared to a high
carbohydrate diet over 12 weeks3. Again, fat loss was greater with more protein, but total weight
loss was similar. Thus, higher protein diets may promote fat loss and preserve lean mass in those
following an energy-restricted diet.
www.AbbottNutritionHealthInstitute.org Page 1 Also, diets with higher protein seem to stimulate satiety, leading to less food intake. Obese adults
provided with a high protein, low carbohydrate diet ad libitum showed similar changes in body
composition and lost the same amount of weight as those given a calorie-controlled low protein,
high carbohydrate diet4. Although the higher protein group was offered unlimited food, this
group reported caloric intakes similar to the group following the lower protein, energy restricted
diet. This finding suggests that the protein level influenced energy intake regulation. In a 4-day
study of weight maintenance, subjects given a high protein diet had increased 24-hour satiety and
decreased hunger when compared to subjects given a lower protein diet5. In addition, 24 hour
satiety was related to protein intake only with the high protein diet.
Molecular Basis for Increased Satiety and Improved Body Weight and Composition
Higher protein diets appear to impact hormonal signaling and metabolic processes related to
weight regulation. Increased satiety from protein is thought to occur due to effects on hormones
such as ghrelin and glucagon-like peptide 1 (GLP-1). Release of ghrelin promotes hunger, while
release of GLP-1 promotes post-meal satiety. A high-protein breakfast decreases postprandial
ghrelin concentration more strongly over time than a high carbohydrate breakfast6. In addition,
increased satiety after a high-protein dinner is significantly related to GLP-15. Thus, protein
affects feeding-related hormone levels.
In regards to body habitus, the molecular basis for improved body composition, specifically,
protein-induced fat loss and LBM retention is unclear. However, recent research indicates that
branched-chain amino acids, particularly leucine, seem to promote muscle anabolism and reduce
fat mass during energy restriction in rats7. When Wistar rats are subjected to food restriction and
supplemented with a low dose of leucine, they show an increase in muscle synthesis and a
decrease in fat mass. In humans, several studies have shown that amino acid supplementation
stimulates muscle protein synthesis and offsets muscle catabolism in those prone to muscle loss,
either due to long periods of bed rest or inactivity8, 9 or sarcopenia10, 11. Thus, the amino acids
provided in protein could play an important role in retaining LBM during times of energy
www.AbbottNutritionHealthInstitute.org Page 2 Concerns relating to Higher Protein Diets
There are existing concerns related to bone and renal health. For example, some question
whether higher protein diets result in bone resorption due to increased urinary calcium. However,
higher protein diets are associated with greater bone mass and fewer fractures when calcium
intake is adequate12. A moderate protein diet providing 30% of calories from protein did not
result in increased urinary calcium13 and, although urinary calcium increased in adults whose
protein intake increased from 0.7 to 2.1 g/kg/day, intestinal calcium absorption increased as well
. Another concern is that higher protein intake may cause an increased risk for impaired kidney
function. In healthy men and women, protein intakes of 2 g/kg/day did not lead to an increase in
impaired kidney function15. However, higher risk groups with already impaired renal function
should avoid high protein diets as higher protein may facilitate a further decline in renal
With rising obesity rates and concerns of sarcopenia in the aging baby boomer population, a
moderate protein diet deserves consideration for weight management. Protein intakes at the
higher end of the AMDR have been demonstrated to curb energy intake, which if sustained, can
lead to weight loss. In addition, moderate protein regimens elicit improved body composition by
reducing fat mass and retaining LBM. At the same time, dietary protein enhances satiety during
energy restriction, lessening the sense of deprivation, which may foster long-term weight loss
success. Some caution is warranted for those with impaired kidney function.
1. Institute of Medicine [Internet]. Dietary Reference Intakes: Macronutrients. [updated 2009 Oct
15; cited 2010 Sept 12]. Available from:
www.AbbottNutritionHealthInstitute.org Page 3 2. Layman, D. K., Evans, E. M., Erickson, D., Seyler, J., Weber, J., Bagshaw, D., et al. A
moderate-protein diet produces sustained weight loss and long-term changes in body
composition and blood lipids in obese adults. The Journal of Nutrition, 2009;139, 514-521.
3. Noakes, M., Keogh, J. B., Foster, P. R., & Clifton, P. M.. Effect of an energy-restricted, highprotein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss,
body composition, nutritional status, and markers of cardiovascular health in obese women.
American Journal of Clinical Nutrition, 2005; 81, 1298-1306.
4. Ebbeling, C. B., Leidig, M. M., Sinclair, K. B., Seger-Shippee, L. G., Feldman, H. A., &
Ludwig, D. S. Effects of an ad libitum low-glycemic load diet on cardiovascular disease risk
factors in obese young adults. American Journal of Clinical Nutrition, 2005;81, 976-982.
5. Lejuene, M., Westerterp, K., Adam, T., Luscombe-Marsh, N., & Westerterp-Plantenga, M.
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. American Journal
of Clinical Nutrition, 2006;83, 89-94.
6. Blom, W., Lluch, A., Stafleu, A., Vinoy, S., Holst, J., Schaafsma, G., et al. Effect of a high
protein breakfast on the postprandial ghrelin response. American Journal of Clinical Nutrition,
2006;83, 211-220.
7. Donato, J., Pedrosa, R., Cruzat, V., Pires, I., & Tirapagui, J. Effects of leucine
supplementation on the body composition and protein status of rats submitted to food restriction.
Nutrition, 2006;22, 520-527.
8. Paddon-Jones, D., Sheffield-Moore, M., Urban, R., Sanford, A., Aarsland, A., Wolfe, R., et al.
Essential amino acid and carbohydrate supplementation ameliorates muscle protein loss in
humans during 28 days of bed rest. Journal of Clinical Endocrinology and Metabolism, 2004;89,
9. Alon T, Bagchi D, Preuss HG. Supplementing with beta-hydroxy-beta-methylbutyrate (HMB)
to build and maintain muscle mass: a review. Research Communications in Molecular Pathology
& Pharmacology, 2002;111, 139-151.
10. Solerte SB, Gazzaruso C, Bonacasa R, Rondanelli M, Zamboni M, Basso C, Locatelli E,
Schifino N, Giustina A, Fioravanti M. Nutritional supplements with oral amino acid mixtures
increases whole-body lean mass and insulin sensitivity in elderly subjects with sarcopenia.
American Journal of Cardiology, 2008;101, 69E-77E.
11. Børsheim E, Bui QU, Tissier S, Kobayashi H, Ferrando AA, Wolfe RR. Effect of amino acid
supplementation on muscle mass, strength and physical function in elderly. Clinical Nutrition,
2008;27, 189-95.
www.AbbottNutritionHealthInstitute.org Page 4 12. Heaney, R., & Layman, D. Amount and type of protein influences bone health. American
Journal of Clinical Nutrition, 2008;87, 1567S-1570S.
13. Nuttall, F., & Gannon, M. The metabolic response to a high protein, low-carbohydrate diet
in men with type 2 diabetes mellitus. Metabolism, 2006;55, 243-251.
14. Kerstetter, J., O'Brian, K., & Insogna, K. Dietary protein, calcium metabolism, and skeletal
homeostasis revisited. American Journal of Clinical Nutrition, 2003;78, S584-S592.
15. Martin WF, Armstrong LE, Rodriguez NR. Dietary protein intake and renal function.
Nutrition & Metabolism, 2005;2, 25.
16. Knight EL, Stampfer MJ, Hankinson SE, Spiegelman D, Curhan GC. The impact of protein
intake on renal function decline in women with normal renal function or mild renal insufficiency.
Annals of Internal Medicine, 2003;138, 460-467.
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