The Metabolic Advantages of Higher Protein Diets

High quality protein is absolutely essential for building lean tissue and promoting recovery from arduous training. But traditionally, higher protein diets have been viewed with a negative connotation and were proposed to cause kidney issues.

Although this viewpoint is totally not supported in the sports medicine field, it is even losing its momentum in the medical community as more and more evidence on the benefits of higher protein intake is being discovered.  

Protein is indispensable to human health and is the primary source of amino acids, the structural components of all body proteins. Inadequate dietary protein intake may result in loss of skeletal muscle mass, as endogenous proteins are rapidly degraded to provide amino acid precursors to sustain protein turnover and energy metabolism.  

To prevent muscle loss, the Institute of Medicine and World Health Organization established recommended dietary allowances (RDA) of 0.8 g/kg/day and 0.83 g/kg/day, respectively.

However, an increase in dietary protein intake can be metabolically advantageous, mainly for overweight and obese adults attempting weight loss, and also for physically active people such as athletes and military personnel, during periods of increased caloric expenditure and metabolic demand (1).

Let’s take a look at some important highlights from the last 10 years of research on the metabolic advantages conferred by consuming higher protein:

Higher protein, healthy weight management & metabolic advantages of dairy protein

The effects of higher protein diets on body composition have been extensively researched. The following are some key points on the effects of higher protein diets in managing bodyweight and benefits of dairy rich protein intake.

• Consuming protein at levels twice the RDA (1.6 g/kg/day) prevents loss of lean body mass and promotes long-term reductions in body fat in overweight and obese individuals during a weight loss program (2). 
• Overweight and obese individuals consuming a dairy-rich (15% of total energy intake), higher protein (30% total energy intake) diet lost more body fat, visceral adipose tissue, and trunk fat when compared to those consuming a standard-protein (15% total energy intake) diet with moderate or low levels of dairy (7.5% and <2% of total energy intake, respectively) over a 16-wk weight loss intervention (3).
• Those consuming the dairy-rich, higher protein diet actually gained lean body mass during the weight loss intervention, an effect likely attributed to enhanced postprandial muscle protein synthetic responses to the high-leucine content of the high-dairy, higher protein diet.  
• Adhering to a higher protein diet may also prevent weight regain and contribute to long-term weight maintenance which is a major concern for many (4). A potential mechanism by which dietary protein contributes to sustained weight maintenance after weight loss could be due to the effect of dietary protein on diet-induced thermogenesis. Thermogenesis is the production of heat, especially in a human or animal body. 
• The metabolic advantages provided by high-dairy diets could reflect independent or synergistic effects of calcium and dairy protein, particularly whey protein, on lipolysis, lipogenesis, and thermogenesis (5).  
• Increased satiety and appetite control may also contribute to improved weight management secondary to consuming higher protein diets (6).

Higher protein and glycemic regulation

Below are some key evidence-based highlights on higher protein and glycemic regulation:  

• Increasing dietary protein intake enhances peripheral insulin sensitivity and is important for individuals with metabolic dysfunction, including insulin resistant people with prediabetes and type 2 diabetes.  
• Cross-sectional studies demonstrate that dairy consumption is inversely related to the incidence of impaired fasting glycemia and type 2 diabetes (7).  
• Although promising, further research is needed before definitive conclusions can be drawn regarding the efficacy of higher-protein, dairy-based diets on glycemic control.

Higher protein on calcium retention and bone health

Protein is a major structural component of bone; therefore, maintaining adequate dietary protein and calcium intake is crucial in order to conserve optimum bone health. Here are some key points on higher protein, calcium retention and bone health.

• The evidence is clear that the current RDA for protein is inadequate to maintain bone health, especially in the elderly.  
• A major concern is that higher protein will increase urinary calcium excretion potentially increasing risk of fracture and osteoporosis. However, the evidence shows that calciuria (i.e., excess calcium in urine) consequent to higher protein diets don’t necessarily diminish calcium balance.  
• Increased calcium excretion secondary to higher protein diets is actually associated with enhanced intestinal calcium absorption. Therefore, calcium balance doesn’t become negative. In fact, higher protein diets enhance calcium absorption and improves endocrine markers of bone health.
• Multiple daily servings of dairy may further enhance benefits of a higher protein intake on intestinal calcium absorption, bone mineral density and long-term biomarkers of bone health.

Latest evidence on higher protein and metabolic regulation? 

Study 1: To date, no inpatient metabolic balance studies have evaluated the exact role of a controlled diet with increased protein on energy expenditure, macronutrient oxidation rates and balances, and metabolic blood markers. In addition, there are no studies with this type of intervention that also utilized state of the art methodology in a controlled environment in healthy males and females with normal body weight.  

A very recent well-designed research study utilized inpatient metabolic balance study to compare the impact of an isocaloric (i.e., same number of calories) high protein vs control diet on energy expenditure, macronutrient oxidation rates and balances, and metabolic blood markers in healthy female and male adults (8).

There were two isocaloric groups with the following diet composition:

1) High protein - 35% carbohydrate, 40% protein, and 25% fat

2) Control - 55% carbohydrate, 15% protein, and 30% fat).

Participants received the prescribed diets for 32 hours while inside a whole-body calorimetry unit.

Key highlights of this study:

• Total energy expenditure was 80 kcals higher in high protein group
• Sleeping energy expenditure higher in high protein group
• Thermic effect of feeding higher in high protein group
• High protein group went into a calorie deficit even though eating same number of calories as other groups
• High protein group Increased fat oxidation, and negative fat balance (likely implying body fat loss)

Conclusion: A high protein diet resulted in greater fat loss compared to an isocaloric diet with lower amounts of protein. With all other things being equal, more protein is beneficial for lean body mass retention and generating greater fat loss. Metabolic advantage to reduced carb is not due to the lower carbs, it’s due to the higher protein intake (8). 

Study 2: Although higher protein diets are gaining popularity worldwide, little is known about the effects on the mechanisms involved in body weight regulation of females and males, especially when associated with exercise. It is important to study the physiological impact of these strategies in a healthy, normal-weight population without the confounding effects of obesity and other comorbidities.

A very recent study investigated the effects of consuming a high-protein meal replacement versus a control breakfast preceding an acute bout of moderate-intensity exercise on selected components of exercise energy metabolism, appetite sensations, and metabolic blood markers in healthy, normal-weight young adults of both sexes (9).

The two isocaloric arms in this study had the following meal composition:

1) High protein - 30% carbohydrate, 43% protein, and 27% fat

2) Control - 55% carbohydrate, 15% protein, and 30% fat

Following breakfast, participants performed a moderate-intensity aerobic exercise while inside a whole-body calorimetry unit. Energy expenditure, macronutrient oxidation, appetite sensations, and metabolic blood markers were assessed.

Key highlights of this study:

• High protein meal led to higher fat oxidation and lower carb oxidation during exercise session.
• Higher protein suppressed hunger and improved metabolic profile after exercise. 

Conclusion: This study showed that, compared to a standard North American breakfast, an isocaloric high protein meal replacement led to higher fat oxidation during exercise, suppression of hunger, and improved metabolic profile after exercise.

These results highlight the benefits of a high protein meal replacement during and after an exercise session on energy metabolism, appetite sensations, and metabolic blood markers of healthy, normal-weight adults of both sexes, and provides further insight into the potential role of these combined strategies for weight management (9).

Summary and practical applications

Increasing dietary protein is safe and can elicit several favorable metabolic adaptations including improved weight management (i.e., fat loss, lean body mass retention, and body weight sustainment), glycemic regulation, calcium retention, and long-term bone health.  

Recent emerging evidence also suggests that consuming dairy may potentiate the metabolic advantages of higher protein diets, primarily due to the digestive, absorptive properties and essential amino acid content of dairy proteins. 

As far as the recommended amount of protein. The two studies above utilized about 2.5 g/kg/bodyweight of protein. Anywhere from 1.6 to 2.4 g/kg/bodyweight or 2.3 to 3.1 g/kg of lean body mass will get you the most benefits from protein.

It’s clear that higher protein enhances fat oxidation at rest and during exercise, increases thermic effect of feeding and total energy expenditure, suppresses hunger and improves our overall metabolic profile.

References 

1. Phillips, S. M. (2014) A brief review of higher dietary protein diets in weight loss: a focus on athletes. Sports Med 44 Suppl 2, S149-153

2. Tang, M., Armstrong, C. L., Leidy, H. J., and Campbell, W. W. (2013) Normal vs. high-protein weight loss diets in men: effects on body composition and indices of metabolic syndrome. Obesity (Silver Spring) 21, E204-210

3. Josse, A. R., Atkinson, S. A., Tarnopolsky, M. A., and Phillips, S. M. (2011) Increased consumption of dairy foods and protein during diet- and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women. J Nutr 141, 1626-1634

4. Larsen, T. M., Dalskov, S. M., van Baak, M., Jebb, S. A., Papadaki, A., Pfeiffer, A. F., Martinez, J. A., Handjieva-Darlenska, T., Kunesova, M., Pihlsgard, M., Stender, S., Holst, C., Saris, W. H., Astrup, A., Diet, O., and Genes, P. (2010) Diets with high or low protein content and glycemic index for weight-loss maintenance. N Engl J Med 363, 2102-2113

5. Zemel, M. B. (2003) Mechanisms of dairy modulation of adiposity. J Nutr 133, 252S-256S

6. Leidy, H. J. (2014) Increased dietary protein as a dietary strategy to prevent and/or treat obesity. Mo Med 111, 54-58

7. Fumeron, F., Lamri, A., Abi Khalil, C., Jaziri, R., Porchay-Balderelli, I., Lantieri, O., Vol, S., Balkau, B., Marre, M., and Data from the Epidemiological Study on the Insulin Resistance Syndrome Study, G. (2011) Dairy consumption and the incidence of hyperglycemia and the metabolic syndrome: results from a french prospective study, Data from the Epidemiological Study on the Insulin Resistance Syndrome (DESIR). Diabetes Care 34, 813-817

8. Oliveira, C. L. P., Boule, N. G., Sharma, A. M., Elliott, S. A., Siervo, M., Ghosh, S., Berg, A., and Prado, C. M. (2021) A high-protein total diet replacement increases energy expenditure and leads to negative fat balance in healthy, normal-weight adults. Am J Clin Nutr 113, 476-487

9. Oliveira, C. L. P., Boule, N. G., Berg, A., Sharma, A. M., Elliott, S. A., Siervo, M., Ghosh, S., and Prado, C. M. (2021) Consumption of a High-Protein Meal Replacement Leads to Higher Fat Oxidation, Suppression of Hunger, and Improved Metabolic Profile After an Exercise Session. Nutrients 13