Intermittent fasting is a dietary approach that involves alternating between periods of eating and fasting. This dietary strategy has gained a lot of popularity in recent years due to its numerous health benefits, including weight loss, improved insulin sensitivity, and reduced inflammation. However, for those following an intermittent fasting plan, the question of how much protein should be consumed during the eating periods is a common one.

Protein is an essential macronutrient that plays a vital role in various bodily functions, including muscle growth, repair, and maintenance. It is also crucial for maintaining healthy bones, skin, and hair. In this article, we will discuss the recommended protein intake for those following an intermittent fasting diet and the scientific evidence behind it.

The Role of Protein in Intermittent Fasting

Intermittent fasting involves a period of fasting followed by a period of feeding. During the feeding period, it is essential to consume adequate amounts of protein to support muscle growth and repair. Research suggests that consuming protein during the feeding period can help preserve lean body mass and improve body composition (1).

Furthermore, protein has a high thermic effect, meaning that it requires more energy to digest and metabolize than other macronutrients, such as carbohydrates and fats. This effect can increase metabolic rate and help burn more calories throughout the day (2). Thus, consuming adequate amounts of protein during the feeding period can be beneficial for weight loss and overall health.

Recommended Protein Intake for Intermittent Fasting

The recommended protein intake for individuals following an intermittent fasting plan varies depending on several factors, such as age, sex, body weight, physical activity level, and goals. The general guideline for protein intake is 0.8 grams per kilogram of body weight per day (g/kg/d) for sedentary individuals (3). However, for those engaging in regular physical activity, the recommended protein intake may be higher to support muscle growth and repair.

According to the International Society of Sports Nutrition (ISSN), athletes and active individuals may require a higher protein intake of 1.4-2.0 g/kg/d (4). This amount can help support muscle protein synthesis and prevent muscle loss during periods of energy restriction, such as intermittent fasting.

Moreover, a study published in the Journal of the International Society of Sports Nutrition found that a high-protein diet (2.3 g/kg/d) during intermittent fasting resulted in greater fat loss and muscle retention compared to a low-protein diet (1.0 g/kg/d) (5). These findings suggest that consuming higher amounts of protein during the feeding period can be beneficial for body composition and weight loss.

Timing of Protein Intake During Intermittent Fasting

The timing of protein intake during the feeding period is another important factor to consider for those following an intermittent fasting plan. Research suggests that consuming protein shortly after exercise can help stimulate muscle protein synthesis and support muscle growth and repair (6).

Moreover, a study published in the American Journal of Clinical Nutrition found that spreading protein intake evenly throughout the day can be more effective for muscle protein synthesis compared to consuming most of the protein at one meal (7). Therefore, individuals following an intermittent fasting plan should aim to distribute their protein intake evenly throughout the feeding period.

Best Protein Sources for Intermittent Fasting

The quality of protein consumed during the feeding period is also essential for muscle growth and repair. High-quality protein sources contain all essential amino acids and are easily digestible. The following are some of the best protein sources for those following an intermittent fasting plan:

1. Lean meats: Chicken, turkey, beef, and pork are excellent sources of high-quality protein. Choose lean cuts to reduce saturated fat intake.

2. Fish: Fatty fish, such as salmon, tuna, and mackerel, are high in protein and also provide omega-3 fatty acids, which can help reduce inflammation and improve heart health.

3. Eggs: Eggs are a rich source of high-quality protein and contain all essential amino acids. They are also rich in vitamins and minerals, making them an excellent addition to any diet.

4. Dairy: Milk, yogurt, and cheese are excellent sources of high-quality protein, calcium, and other essential nutrients. However, individuals following an intermittent fasting plan should choose low-fat or fat-free dairy products to reduce calorie and saturated fat intake.

5. Plant-based protein: Vegetarians and vegans can obtain adequate amounts of protein from plant-based sources such as legumes, tofu, tempeh, nuts, and seeds. However, plant-based protein sources may be lower in certain essential amino acids, so it is essential to consume a variety of protein sources to ensure adequate intake of all essential amino acids.

Potential Risks of Consuming Too Much Protein

While consuming adequate amounts of protein during the feeding period is essential for muscle growth and repair, consuming too much protein can also have adverse effects on health. Excess protein intake can strain the kidneys, leading to kidney damage and other health problems (8).

Moreover, consuming high amounts of protein from animal sources, such as red meat and processed meat, has been linked to an increased risk of certain cancers, such as colon cancer (9). Therefore, it is essential to choose lean protein sources and consume a variety of protein sources to minimize the risks.

Conclusion

Consuming adequate amounts of protein during the feeding period is essential for those following an intermittent fasting plan. The recommended protein intake varies depending on several factors, such as age, sex, body weight, physical activity level, and goals. The general guideline for protein intake is 0.8 grams per kilogram of body weight per day (g/kg/d) for sedentary individuals, while athletes and active individuals may require a higher protein intake of 1.4-2.0 g/kg/d.

Moreover, the timing and quality of protein intake are also essential factors to consider. Consuming protein shortly after exercise and spreading protein intake evenly throughout the feeding period can be beneficial for muscle growth and repair. Choosing high-quality protein sources, such as lean meats, fish, eggs, dairy, and plant-based protein, can help ensure adequate intake of all essential amino acids.

While consuming adequate amounts of protein is important for health, it is also essential to avoid consuming too much protein, which can have adverse effects on health. Therefore, it is essential to choose lean protein sources and consume a variety of protein sources to minimize the risks.

In conclusion, consuming adequate amounts of high-quality protein during the feeding period is essential for those following an intermittent fasting plan to support muscle growth and repair, improve body composition, and promote overall health. By following the recommended guidelines for protein intake, timing, and quality, individuals can maximize the benefits of intermittent fasting while minimizing the risks.

References

1. Longland TM, Oikawa SY, Mitchell CJ, et al. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016;103(3):738-746. doi:10.3945/ajcn.115.119339

2. Westerterp KR. Diet induced thermogenesis. Nutr Metab (Lond). 2004;1(1):5. doi:10.1186/1743-7075-1-5

3. Institute of Medicine (US) Committee on Use of Dietary Reference Intakes in Nutrition Labeling. Dietary Reference Intakes: Guiding Principles for Nutrition Labeling and Fortification. National Academies Press (US); 2003.

4. Campbell B, Kreider RB, Ziegenfuss T, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2007;4:8. doi:10.1186/1550-2783-4-8

5. Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Int Soc Sports Nutr. 2018;15:41. doi:10.1186/s12970-018-0242-z

6. Beelen M, Koopman R, Gijsen AP, et al. Protein co-ingestion stimulates muscle protein synthesis during resistance-type exercise. Am J Physiol Endocrinol Metab. 2008;295(1):E70-E77. doi:10.1152/ajpendo.90205.3368

7. Mamerow MM, Mettler JA, English KL, et al. Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. J Nutr. 2014;144(6):876-880. doi:10.3945/jn.113.185280

8. Knight EL, Stampfer MJ, Hankinson SE, et al. The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency. Ann Intern Med. 2003;138(6):460-467. doi:10.7326/0003-4819-138-6-200303180-00006

9. World Cancer Research Fund International/American Institute for Cancer Research. Continuous Update Project Expert Report 2018. Available at: https://www.wcrf.org/dietandcancer/cancer-trends/data-cancer-frequency-country/colon-and-rectum-cancer-facts-and-figures. Accessed on 27 April 2023.