Protein: how much, and why

Three numbers, three purposes

Protein advice sounds contradictory because it answers different questions. Three published figures are worth keeping apart.

0.8 g/kg/day is the adult Recommended Dietary Allowance. It has been essentially unchanged for more than 70 years and was derived to estimate the minimum amount that must be eaten to avoid a loss of body nitrogen (Wolfe et al., 2017). It answers “what is the least that covers need?”

10 to 35 percent of calories is the Acceptable Macronutrient Distribution Range for adults (Dietary Guidelines, 2020–2025). The authors of a 2017 review in Advances in Nutrition note that the lowest protein intake the range reflects is higher than the RDA (Wolfe et al., 2017).

1.4 to 2.0 g/kg/day is the range the International Society of Sports Nutrition gives as sufficient for most exercising people, whether the aim is building or maintaining muscle (ISSN position stand, 2017). That position stand is written for healthy, exercising individuals.

What the meta-analysis found

Morton and colleagues pooled 49 randomized trials with 1,863 participants. The trials all combined resistance training of at least six weeks with protein supplementation. Supplementation increased gains in muscle size and strength, and the benefit was smaller with older age and larger in people with more training experience. In their break-point analysis, total intakes above about 1.6 g/kg/day produced no further gains in fat-free mass (Morton et al., 2018).

Read that for what it is. It is a finding about people lifting weights, in trials that added protein, with gains in muscle as the outcome. It is one reason 1.6 g/kg shows up so often as a round number. It is not a rule for everyone.

Find your grams

Multiply your body weight in kilograms by the figure that fits you. To work from pounds, divide by 2.2 first, or use the per-pound equivalents of 0.64 to 0.91 g/lb for the 1.4 to 2.0 range.

Per meal, not just per day

The same position stand says recommendations for the best amount per serving are mixed and depend on age and recent resistance exercise, with general guidance of 0.25 g of high-quality protein per kg of body weight, or an absolute dose of 20 to 40 g. It suggests spreading doses fairly evenly, about every 3 to 4 hours across the day (ISSN position stand, 2017). For a 70 kg person, 112 g a day over four meals is 28 g each, which sits comfortably inside that window.

Where it gets specific

The same ISSN document describes higher intakes, 2.3 to 3.1 g/kg/day, as something that may be needed to maximize retention of lean mass in resistance-trained people eating below their maintenance calories (ISSN position stand, 2017). That is a narrow case with a specific goal. It is not a default.

If you have kidney disease or another medical condition, if you are pregnant, or if you are managing a reduced appetite, the ranges above are not a substitute for what your clinician or dietitian has told you. Use their numbers.

A note on food and supplements

The ISSN position stand notes that it is possible for physically active people to get their daily protein from whole foods, and that supplements are a convenient way to ensure quantity and quality while keeping calories down (ISSN position stand, 2017). Whether you use one is a preference, not a requirement. What matters for the arithmetic is the grams: read the label, weigh the portion, and count what you eat.

How we use this

In MacroCrafted you set protein as a grams target, and the engine treats it as a floor when it builds and checks a meal. Which figure you choose is up to you. The table above is a place to start, not a prescription.