Few nutrition questions generate more noise than protein requirements. At one end, official dietary reference intakes suggest levels that exercise physiologists consider inadequate for active people. At the other end, supplement industry messaging implies that massive protein intakes are essential for anyone who steps inside a gym. The research sits in a more nuanced middle ground, and understanding it produces useful guidance.
The Official Recommendation and Why It's Misleading
The Recommended Dietary Allowance (RDA) for protein in the United States is 0.8 grams per kilogram of body weight per day. For a 70kg (154lb) adult, that's about 56 grams of protein per day. This is frequently cited and consistently misunderstood.
The RDA is defined as the amount sufficient to meet the needs of 97.5% of the healthy sedentary population. It is a floor, not a target. It is the amount required to prevent deficiency, not the amount that optimizes health or supports physically active people. Using the RDA as a target for someone who exercises regularly is like using famine-prevention calorie thresholds as weight management guidance.
What the Research Supports for Muscle Maintenance and Growth
For adults who engage in regular resistance training and want to build or maintain muscle mass, the evidence consistently supports higher protein intakes than the RDA. A comprehensive meta-analysis of 49 randomized controlled trials (Stuart Phillips et al., 2017) found that protein supplementation significantly increased muscle mass and strength gains in response to resistance training, with no additional benefit observed above approximately 1.62 grams per kilogram of body weight per day.
Translated for a 70kg person: roughly 113 grams of protein per day appears to be the upper end of the dose-response curve for muscle protein synthesis. Consuming more than this doesn't meaningfully accelerate muscle growth, though it doesn't cause harm at moderate excesses.
For older adults, the protein requirement for muscle maintenance is higher than for younger adults due to "anabolic resistance" — the reduced sensitivity of aging muscle to the muscle-building stimulus of protein. Research in this area supports intakes of 1.2-1.6 grams per kilogram per day for adults over 60 who want to preserve muscle mass.
For fat loss while maintaining muscle (the scenario most people are actually trying to navigate), higher protein intakes — up to 2.0-2.4 grams per kilogram per day — appear beneficial. Protein is the most satiating macronutrient, it has the highest thermic effect (more calories burned in digestion), and it is most protective of lean mass during caloric restriction.
Does Protein Timing Matter?
The "anabolic window" concept — the idea that protein consumed immediately after exercise is uniquely valuable — has been significantly revised by more recent research. While consuming protein around workouts is not harmful, the notion that missing a 30-minute window negates gains is not supported by evidence.
What appears to matter more is total daily protein intake and its distribution across meals. Research supports spreading protein intake relatively evenly across three or more meals, with each meal providing enough leucine (a key signaling amino acid) to maximally stimulate muscle protein synthesis — roughly 20-40 grams of high-quality protein per meal depending on individual factors.
Protein consumed before sleep — specifically casein, due to its slow digestion — has shown consistent benefits in studies on overnight muscle protein synthesis, suggesting that the bedtime protein shake recommendation has more evidence behind it than most.
Protein Quality
Not all protein sources are equivalent. Protein quality is determined by the amino acid profile (complete proteins contain all essential amino acids) and digestibility.
Animal proteins (meat, fish, eggs, dairy) are complete and highly digestible. Plant proteins are often limiting in one or more essential amino acids, but eating a variety of plant protein sources throughout the day effectively addresses this without requiring obsessive food combining. Soy is the most complete plant protein, roughly equivalent to animal sources in leucine content and muscle protein synthesis stimulation.
For people eating predominantly plant-based diets, the practical advice is to target slightly higher total protein intakes (perhaps 10-15% higher) to account for lower average digestibility, and to prioritize high-leucine plant sources: soy foods, lentils, and to some extent chickpeas and black beans.
Practical Targets
For most active adults:
- Sedentary: 0.8-1.0 g/kg/day (the RDA is adequate)
- Moderately active, maintaining weight: 1.2-1.4 g/kg/day
- Actively training for muscle gain: 1.4-1.6 g/kg/day
- Cutting calories while maintaining muscle: 1.8-2.2 g/kg/day
- Older adults (65+) focused on muscle preservation: 1.2-1.6 g/kg/day
For a 70kg person training for muscle gain, 100-112 grams per day covers the range. That's achievable through whole food sources — three to four palm-sized servings of protein-dense foods throughout the day — without heroic supplement use.
The research on protein requirements has matured considerably in the past decade. The picture that emerges is not the extreme of "protein doesn't matter beyond minimal amounts" nor the other extreme of "more is always better." It's a dose-response relationship with a practical ceiling, and most people who exercise regularly benefit from paying attention to it.
