Protein while cutting: why 1.6 g/kg is not the whole story

Where the familiar 1.6 figure comes from

The Morton meta-analysis published in 2018 pooled 49 resistance-training studies and reported a breakpoint around 1.62 g/kg/day for additional fat-free-mass gains with protein supplementation. That group-level estimate is often repeated as a hard ceiling. It was not a universal rule for every person dieting, and a breakpoint analysis is not a measurement of your personal requirement.

The 2026 review asks about a deficit

An updated review by Refalo, Trexler and Helms, appearing in the August 2026 journal issue, analyzed 29 studies in nonobese, resistance-trained people under energy restriction. Higher protein intake was associated with more favorable fat-free-mass change. The relationship was stronger when intake was expressed relative to fat-free mass and at lower body-fat levels.

The authors described the findings as exploratory because the studies differed substantially. Meta-regression compares patterns across studies; it does not randomly assign everyone to an unlimited sequence of protein doses. It cannot establish that each extra gram causes a predictable gain.

What October’s position stand adds

The ISSN position stand published on 13 October 2026 also treats protein in the context of lean-mass retention during weight reduction. It emphasizes population and body-size context, including why using current body weight can overstate a gram-per-kilogram target for someone with obesity. That is a reason to individualize the assumption, not to multiply every person’s scale weight by the largest number available.

What the arithmetic can—and cannot—tell you

For an invented 80 kg example, 1.6 g/kg/day equals 128 g of protein and 2.0 g/kg/day equals 160 g. The difference is 32 g. Using the usual bookkeeping factor of 4 kcal per gram, that represents 128 kcal before considering what foods or nutrients it replaces.

This calculation does not establish which intake is appropriate. It makes the trade-off visible. If total energy is fixed, allocating more energy to protein changes what remains for carbohydrate and fat. If total energy rises instead, you have changed two assumptions, not just one.

A useful note beside a target therefore says which body weight you used, what the g/kg assumption represents and how it fits the rest of the diet. That is more transparent than treating a calculator output as a laboratory finding.

Use a calculator to inspect a choice, not certify it

Our protein tool applies your chosen assumption to total body weight. Its default is an example; its input range is a software boundary rather than a clinical recommendation. The macro tool then shows the remaining allocation.

These studies cannot identify an individual target from body weight alone. People with medical nutrition needs should use an appropriately qualified clinician or dietitian rather than extrapolating a research range from lean, trained participants.