How Much Protein Do You Really Need for Resistance-Training?

Key points:

• The well-known recommendation of 1.6 grams of protein per kg of bodyweight is less precise than what most people think.

• Intakes of 1.0 to 2.2 grams per kg of bodyweight are statistically just as likely to be suitable.

• There is little evidence to support drastic increases in protein intake to preserve muscle mass during periods of weight loss.

Article Overview and Helpful Definitions:

This article covers protein recommendations for anyone involved in or planning to start resistance training, with the goal of maintaining or building muscle. Resistance training refers to strength-focused activities like weightlifting, bodyweight exercises, or machine-based workouts aimed at improving strength or muscle mass. If resistance training isn’t your thing or you’re more focused on endurance activities like cardio, you probably don’t need to worry about protein levels—your standard diet should have you covered. In that case, feel free to stop reading and save yourself some time!

We’ll also touch on macronutrients and calories. Macronutrients, or “macros,” are the nutrients your body needs in large amounts to provide energy and support growth, repair, and essential functions. They’re split into three categories: carbohydrates, proteins, and fats. Carbohydrates are your body’s main energy source, breaking down into glucose to fuel your cells, and are found in foods like grains, fruits, vegetables, and dairy. Proteins are key for building and repairing tissues, making enzymes and hormones, and supporting your immune system; you’ll find them in meat, fish, eggs, dairy, legumes, nuts, and seeds. Fats provide a concentrated energy source, help with cell structure, hormone production, and absorption of vitamins like A, D, E, and K, and are found in oils, butter, avocados, nuts, seeds, and fatty fish. Lastly, calories measure the energy a food or drink provides, powering everything from breathing and digestion to physical activity.

Introduction:

I don’t spend much time on typical social media, but I do consume a lot of YouTube content, especially recipes and cooking techniques. I justify this as “educational.” Recently, I watched a video by Joshua Weissman, a popular food YouTuber who achieved significant weight loss through strict dieting and exercise—an impressive accomplishment!

While watching, two things stood out: the massive amount of protein he was eating and what seemed like excessive exercise for his goals (a topic for another time). For now, let’s focus on the protein. Before diving in, I want to clarify that this isn’t a critique of Joshua but rather a reflection on the protein ideologies common in the health and fitness world. In the video, Joshua ate 2,460 calories daily, slightly below the average caloric intake for a male (~2,500 calories). He managed to lose weight at this level likely due to his intense exercise routine—two to two and a half hours daily, six days a week (not necessary for weight loss, but again, a story for another time!). His daily macronutrient breakdown was 60 grams of fat, 160 grams of carbohydrates, and an astonishing 320 grams of protein.

To put that into perspective, 320 grams of protein is a lot—roughly equivalent to over a kilogram of chicken breast or 11+ protein shakes daily. It’s about 4g of protein per kilogram of his body weight, which is extremely high! Eating this much protein means significantly reducing fats and carbs to stay within daily caloric limits, leaving little flexibility in the diet. For someone who loves food, it must have been tough to stick to such restrictions.

Yes, resistance-trained individuals are often advised to increase protein intake to maintain muscle while losing weight, but 320 grams per day seems excessive. So, what does research actually recommend when it comes to protein intake? Let’s dive into that in the next sections!

General Protein Recommendations for Resistance-Training:

To explore this, let’s delve into the basis of protein recommendations for individuals engaging in resistance training, setting weight loss aside for now. If you’re familiar with tracking macronutrients, you’ve probably come across the recommendation of 1.6 grams of protein per kilogram of body weight per day (1.6 g/kg/d).

This common recommendation originates from a 2018 paper by Morton (2018) [1] which conducted a “meta-analysis.” Simply put, a meta-analysis compiles data from multiple related studies to identify trends across the research. Think of it as a study where the participants are individual research papers. In theory, this is the strongest form of evidence, but only when performed correctly and using high-quality studies.

One of Morton’s research questions examined how much protein is needed to optimise muscle growth from resistance training. The most cited part of their findings relates to the relationship between daily protein intake (g/kg/d) and increases in fat-free mass over the course of a study. Fat-free mass includes everything in the body that isn’t fat—such as muscle, organs, bones, and water. While it doesn’t directly measure muscle mass, it’s a good indicator since higher fat-free mass generally correlates with greater muscle mass. Plus, other tissues (like organs) don’t significantly change in size due to resistance training, so increases in fat-free mass are often attributed to muscle growth.

The analysis suggested that protein intakes above 1.6 g/kg/d may not lead to further notable increases in fat-free mass (see Figure 1 for the plot). However, the often-overlooked detail is the confidence interval of this estimate, which reflects the range within which we’re 95% confident the true value lies. For 1.6 g/kg/d, the confidence interval ranges from 1.0 to 2.2 g/kg/d. This means an individual might optimise fat-free mass gains with a protein intake anywhere within this range.

One caveat to consider is the variation in the studies included in this meta-analysis, which examined both trained and untrained individuals. Untrained individuals are likely to experience significant increases in fat-free mass even with suboptimal protein intake. On the other hand, trained individuals may require more effort to consume enough protein to see improvements. This distinction could influence the results and the generalisability of the findings.

Figure 1. Plot from Morten (2018) [1] presenting the relationship between the change in fat free mass (FFM) and Total Protein Intake (g/kg/d). The blue dots represent individual studies analysed in the analysis, each with a different level of daily protein intake. The plot is fitted with two linear lines which indicate increasing protein intake up to 1.6 g/kg/d provides some benefit in increasing FFM. The 1.6 g/kg/d recommendation can be seen by the red dashed line while the confidence intervals of 1.0 and 2.2 g/kg/d can be seen in the black dashed lines.

While not a flawless analysis, the recommendation of 1.6 g/kg/d provides sufficient protein for most individuals to achieve near-optimal increases in fat-free mass. While the study suggests a broad range of suitable protein intakes, adopting a more conservative approach—aiming for 1.6 g/kg/d or slightly more—can increase confidence in maximising the benefits of resistance training and diet. However, it’s important to note that this recommendation doesn’t specifically account for weight-loss periods.

Since Morton’s work, three additional studies have performed similar analyses focusing on resistance-trained individuals. They’ve reported comparable recommendations of 1.5, 1.7, and 2.0 g/kg/d [2-4]. Even with less varied populations, these studies also showed wide confidence intervals, reflecting some uncertainty around the precise optimal intake.

In summary, 1.6 g/kg/d is a solid guideline for ensuring sufficient protein to optimise or nearly optimise muscle growth. However, aiming slightly below this threshold (e.g., 1.4 g/kg/d) or occasionally falling short is unlikely to significantly impact muscle gains. The same analysis supporting the 1.6 g/kg/d recommendation also supports this flexibility. So, stressing over exact protein intake may not be necessary, especially if your diet already prioritises high-quality meals (e.g., balanced distributions of protein sources, grains, vegetables, and fruits). These recommendations are also particularly relevant for those maintaining or increasing body weight, as bulking doesn’t appear to require higher protein levels.

Protein Recommendations While Losing Weight:

Let’s briefly dive into protein recommendations for individuals trying to lose weight while maintaining or even increasing their muscle mass. During weight loss, when you’re consuming fewer calories than needed to sustain your activity levels, the body breaks down tissue to make up the energy shortfall. This primarily targets fat tissue but can also lead to some loss of lean mass. To counteract this, it’s often recommended to increase protein intake during weight loss to help preserve muscle mass. After all, no one wants to lose the muscle they’ve worked so hard to build!

Some people aim for very high protein intakes (e.g., 3-4 g/kg/d), but these can be difficult to achieve without significantly cutting fat and carbohydrate intake, which isn’t always ideal. However, research doesn’t entirely back up the need for such extreme protein consumption. Reviews suggest more moderate ranges of 1.8–2.7 g/kg/d or 1.3–1.8 g/kg/d, with studies showing that higher protein levels generally improve lean mass retention during weight loss.

For example, Walberg (1988) [5] found that 1.6 g/kg/d preserved lean mass better than 0.8 g/kg/d in a one-week study, while Mettler (2010) [6] showed that 2.3 g/kg/d outperformed 1.0 g/kg/d over two weeks. Another study comparing 1.6 g/kg and 2.8 g/kg of protein during a two-week period found no significant differences in lean mass retention or fat loss [7]. Longland (2016) reported that 2.4 g/kg/d led to better body composition outcomes than 1.2 g/kg/d over four weeks [8].

While these studies are limited by their short duration (1-4 weeks) and sometimes unusual comparisons (e.g., 1.0 vs. 2.3 g/kg/d), they suggest that a protein intake of 1.6–2.4 g/kg/d is likely sufficient for retaining lean mass during weight loss. This range isn’t far off from the recommendations for maintaining or gaining muscle under normal conditions.

It’s worth noting that your ideal protein intake during weight loss depends on several factors, including how aggressively you’re losing weight, your starting levels of fat and lean mass, and your training history. Faster weight loss typically leads to greater muscle loss, so adopting a moderate approach (e.g., reducing daily caloric intake by 10-20%) may reduce the need for additional protein. Additionally, those who are relatively untrained or starting with higher body fat percentages (e.g., over 28% for males or 40% for females) tend to lose less muscle during weight loss compared to leaner individuals.

Finally, the most critical factor for preserving muscle mass during weight loss is continuing resistance training at a similar level to your usual routine. This sends the right signals to your body to hold onto muscle, even as you shed fat. So, if you’re cutting calories, don’t skip the weights!

Summary:

In summary, the widely shared protein recommendations are less rigid than they’re often portrayed to be, and intakes below these levels might still work well for you based on the underlying research. Similarly, if you’re already consuming 1.6–2.2 g/kg/d of protein, there’s little need to significantly increase this during weight loss, especially if you’re resistance training.

This nuanced understanding allows for greater flexibility in your diet and macronutrient distribution, freeing you from overly strict targets. Whether you prefer a diet higher in protein or one that balances macronutrients differently, it’s more important to choose what works for your goals, lifestyle, and preferences—as long as it doesn’t negatively impact others. So, if a higher protein intake makes you feel good and fits your routine and budget, there’s no reason to change it. The key is finding an approach that you enjoy and can sustain while achieving your desired outcomes.

References

1. Morton RW, Murphy KT, McKellar SR, Schoenfeld BJ, Henselmans M, Helms E, et al. A Systematic Review, Meta-Analysis And Meta-Regression Of The Effect Of Protein Supplementation On Resistance Training-Induced Gains In Muscle Mass And Strength In Healthy Adults. Br J Sports Med. 2018 Mar;52(6):376–84.

2. Murphy, C.H., A.J. Hector, and S.M. Phillips, Considerations for protein intake in managing weight loss in athletes. European Journal of Sport Science, 2015. 15(1): p. 21-28.

3. Jager, R., et al., International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr, 2017. 14: p. 20.

4. Phillips, S.M. and L.J. Van Loon, Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci, 2011. 29 Suppl 1: p. S29-38.

5. Walberg, J.L., et al., Macronutrient content of a hypoenergy diet affects nitrogen retention and muscle function in weight lifters. Int J Sports Med, 1988. 9(4): p. 261-6.

6. Mettler, S., N. Mitchell, and K.D. Tipton, Increased protein intake reduces lean body mass loss during weight loss in athletes. Medicine and Science in Sports and Exercise, 2010. 42(2): p. 326-37.

7. Helms, E.R., et al., High-protein, low-fat, short-term diet results in less stress and fatigue than moderate-protein moderate-fat diet during weight loss in male weightlifters: a pilot study. Int J Sport Nutr Exerc Metab, 2015. 25(2): p. 163-70.

8. Longland, T.M., 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): p. 738-46.