Optimal Protein Intake for Muscle Growth After Resistance Training

By Chris Bigelow

If you enjoy resistance training, you’ve probably asked yourself at some point: “How much protein do I actually need to grow?” Many people overestimate how much protein they need while underestimating the importance of other factors like training quality, recovery, and overall diet.

In this article, we’ll focus on protein intake and break down some of the latest research-based recommendations. Specifically, we’ll review Iraki et al. (2019), a well-cited study titled Nutrition Recommendations for Bodybuilders in the Off-Season: A Narrative Review. I chose this study because bodybuilders spend a significant amount of time fine-tuning their training and nutrition for muscle growth, and this review has been cited over 100 times since its publication due to its comprehensive coverage of the topic. The review also mentioned that even though the population was body builders the principles still apply broadly to individuals engaging in resistance training.

It's also important to note that this study is a narrative review, meaning it doesn’t introduce new research but instead interprets existing scientific literature to form evidence-based recommendations.

So, How Much Protein Do You Need to Optimally Recover After Resistance Training?

Iraki et al. (2019) recommend a minimum of 1.6 grams of protein per kilogram (g/kg) of body weight for muscle growth, but 2.2 g/kg may be better for optimizing lean mass gains in athletic populations. These recommendations apply to both men and women, as the numbers were adjusted for fat-free mass (FFM) rather than total body weight.

Converting Kilograms to Pounds

If you’re unfamiliar with the metric system, here’s how to calculate your protein needs:

• 1 kilogram (kg) = 2.2 pounds (lbs)

• To convert your body weight to kilograms, divide by 2.2

For example, if someone weighs 200 lbs:
200 lbs ÷ 2.2 = 90.9 kg

Using the recommended range:

• Lower end (1.6 g/kg): 90.9 × 1.6 = 146 g of protein/day

• Upper end (2.2 g/kg): 90.9 × 2.2 = 200 g of protein/day

A simple rule of thumb? The high end of the range is roughly 1 gram of protein per pound of body weight.

How Much Protein Should You Consume Per Meal?

A common question is how much protein the body can utilize from a single meal. Iraki et al. (2019) discuss research indicating that consuming 20 g of protein per meal is sufficient to maximize muscle protein synthesis. However, they also note that 40 g of protein per meal can provide a greater muscle-building response if a higher volume of muscle is worked. This suggests that while 20 g per meal is a good baseline, individuals performing more intense or full-body workouts may benefit from slightly higher single-meal protein intakes.

Why Use Body Weight Instead of a Percentage of Calories?

You might be wondering why protein recommendations are based on body weight instead of a percentage of total calories—after all, many general dietary guidelines use macronutrient percentages (e.g., 10–35% of calories from protein).

However, Iraki et al. (2019) note that percentage-based recommendations can be misleading, especially in their hypothetical example of a lightweight athletes with high calorie requirements. If protein intake is set as a percentage of total calories, some individuals may end up eating too much protein at the expense of essential carbohydrates and fats.

By using body weight, protein intake is scaled appropriately without disrupting the overall balance of macronutrients in your diet.

Does Protein Quality Matter?

Yes—but only to a certain extent.

Iraki et al. (2019) highlight leucine as an important amino acid because it acts as a “metabolic trigger” for muscle protein synthesis (MPS). High-quality protein sources contain enough leucine and enough total protein to help you reach your daily intake goal.  This means you probably don't have to worry about supplementing with specific amino acids, like leucine, as long as your protein sources are high quality.

However, if total daily protein intake is sufficient, the exact protein source becomes less important in the long run. This suggests that hitting your protein target is more critical than focusing on specific “high-quality” sources—though quality matters more if you’re consuming protein at the lower end of the range (1.6 g/kg).  Examples of high-quality sources include, but are not limited to: Eggs, fish, lean meats and whey protein supplements.

Does Protein Timing Matter?

One of the most surprising insights from the review is that timing protein intake immediately post-workout may not be as crucial as commonly believed.

While consuming protein right after training does lead to a greater peak in muscle protein synthesis, research suggests this does not translate into greater long-term lean mass gains—provided total daily protein intake is met.

This runs counter to much of the advice seen on social media, where "anabolic windows" are often overemphasized.

That said, it’s still a good idea to consume a meal or shake containing both protein and carbohydrates after training. While protein timing may not significantly impact muscle growth to the extent as many believe, post-workout carbohydrate intake helps replenish glycogen, which plays a key role in training intensity and recovery. Carbohydrate timing, unlike protein timing, has clear performance benefits—but we’ll cover that in a future article.

Final Thoughts

Iraki et al. (2019) provide a thorough, evidence-based look at nutrition for bodybuilders and resistance-trained individuals. Their findings reinforce that:
🔹 1.6–2.2 g/kg of protein is ideal for muscle growth
🔹 Protein quality matters—but total daily intake matters more
🔹 Protein timing is less important than overall protein intake
🔹 A slow, controlled calorie surplus is best for lean muscle gain
🔹 A meal with 20–40 g of protein is sufficient, with higher amounts beneficial after large muscle-group training sessions

If you’re interested in diving deeper into the full narrative review, which covers much more than just protein, you can read it for free linked below.  If you have taken our Health And Wellness Education Course, you may want to use the provided engineered AI prompt in the course for analyzing research papers to quickly summarize the study:
🔗 Iraki et al. (2019) - Full Study

Reference

Iraki, J., Fitschen, P., Espinar, S., & Helms, E. (2019). Nutrition Recommendations for Bodybuilders in the Off-Season: A Narrative Review. Sports (Basel, Switzerland), 7(7), 154. https://doi.org/10.3390/sports7070154

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