Most people trying to lose weight and keep muscle have been told to eat more protein. That part is correct. What often goes wrong is the arithmetic. The standard advice is to multiply your body weight in kilograms by a target in grams per kilogram. The problem is which body weight you use. For people with significant excess fat, the answer changes the result a lot. Using the wrong number sets a target that is either inflated and too hard to hit, or missed because it felt unreachable from the start.

Why your actual weight is not the right base

Protein requirements are driven mainly by lean mass: the muscle, organ, and bone tissue that turns over, repairs itself, and responds to training. Fat mass contributes very little to protein turnover. When someone with a BMI above 25 uses their actual body weight as the base for protein calculations, they are treating their fat tissue as though it had the same protein demands as lean tissue. It does not.

The German Nutrition Society (DGE) is explicit about this. Its reference values for protein (0.8 g/kg per day for adults under 65, 1.0 g/kg from 65 onwards) are stated with reference to normal body weight. For people with overweight or obesity, the DGE guidance is to calculate from normal weight, not from actual weight. The European Food Safety Authority (EFSA) sets its population reference intake at 0.83 g/kg, with the same implicit assumption: the denominator is a weight that reflects metabolically relevant mass.

Intervention studies compound the problem. Protein intakes in research are usually reported as grams per kilogram of actual body weight, which makes the numbers look higher for heavier participants even when the underlying biological targets are similar. Comparing studies with different participant weights is hard, and you cannot read off a study's headline figure and apply it to yourself without knowing how they measured.

Fat mass does not drive protein requirements proportionally. Using actual weight when you carry significant excess fat sets a target based on tissue that has no particular need for the protein you assign it.

The practical fix: calculate from target or adjusted weight

The more useful approach is to calculate protein from your target weight, or an adjusted body weight that reflects where you are heading rather than where you currently are. This is not a workaround. It is the correct denominator when the goal is to preserve lean mass during fat loss.

The practical anchor from the evidence is 1.3 to 1.5 g of protein per kilogram of target or adjusted body weight per day. This sits above the baseline reference values, which is appropriate during a weight-loss phase. Energy restriction creates a catabolic environment, and higher protein intake helps counteract muscle loss even without intensive training. A 2015 review by Leidy and colleagues found that intakes of 1.2 to 1.6 g/kg, with roughly 25 to 30 grams at each main meal, were associated with better appetite control, better body composition during weight loss, and more lean mass preservation. A 2012 meta-analysis by Wycherley and colleagues, covering 24 randomised controlled trials and over 1,000 participants on energy-restricted diets, found that higher-protein groups lost about 0.8 kg more fat and kept about 0.4 kg more lean mass than standard-protein groups.

A 2024 systematic review and meta-analysis by Kokura and colleagues, covering 47 RCTs and 3,218 participants with overweight or obesity, found that intakes above 1.3 g/kg per day significantly reduced muscle mass loss during weight loss, while intakes below 1.0 g/kg were associated with greater muscle loss. The evidence converges on the same answer: for adults in a caloric deficit, the 1.3 to 1.5 g/kg range is a solid target, and the denominator should be target or adjusted weight.

Two examples

A 61-year-old man weighing 106 kg with a target weight of 92 kg uses 92 as his base. At 1.3 to 1.5 g/kg, that yields a daily protein target of roughly 120 to 138 grams. If he used his actual weight of 106 kg at the same multiplier, the target would be 138 to 159 grams, based on a number that includes about 14 kilograms of fat he is trying to lose. The adjusted calculation is not conservative. It is accurate.

A parallel example for a woman: 52 years old, currently 78 kg, with a target weight of 68 kg. Using 68 as the base at 1.3 to 1.5 g/kg gives a daily protein target of roughly 88 to 102 grams. This is reachable through ordinary food, without protein supplements. Three meals of 25 to 35 grams of good-quality protein will land in this range. Using her actual weight of 78 kg at the same multiplier would give 101 to 117 grams, an overshoot that could make the target feel burdensome and is not supported by the biology.

What the evidence supports

For adults 40 and over, there is another layer. The PROT-AGE consensus paper (Bauer et al., 2013), one of the most-cited position papers on protein and ageing, recommended 1.0 to 1.2 g/kg for healthy older adults to maintain lean mass, rising to 1.2 g/kg or above with regular physical activity, and up to 1.5 g/kg during illness or physiological stress. Deutz and colleagues (2014), writing for ESPEN, supported similar ranges. Ageing muscle is less sensitive to dietary protein, so older adults need more protein per meal to trigger the same anabolic response a smaller dose would produce in a younger adult. This blunted response, often called anabolic resistance, is well established. It is one reason the 0.8 g/kg minimum that is adequate for a 30-year-old is insufficient for someone in their fifties or sixties trying to keep muscle during a caloric deficit.

Weijs and Wolfe (2016), working with obese older adults during active weight loss, found that a threshold of at least 1.2 g/kg of actual body weight, or about 1.9 g/kg of fat-free mass, was associated with better muscle retention. Their work shows the same structural problem: when you have substantial fat mass, the fat-free mass denominator is the biologically meaningful one, and any calculation based on total body weight risks understating the requirement relative to the tissue that matters.

A 2025 review by Weijs in Current Opinion in Clinical Nutrition and Metabolic Care updates the evidence and reaches a consistent conclusion: during weight loss in adults with obesity, protein should be calculated from a capped body weight (the author uses a weight at BMI 30 as the ceiling rather than actual weight), with a minimum of 1.2 g/kg of that capped weight per day, and more in older adults. The review also notes a caveat worth keeping in mind: an obese person with an active lifestyle may have normal protein requirements, so context matters beyond BMI alone. The 1.3 to 1.5 g/kg target range used in this article sits above that floor and is consistent with the broader body of evidence on muscle retention during energy restriction.

Why this matters more, not less, for women 40 and over

The perimenopause and postmenopause transition changes the equation in ways that are often missing from general protein advice. Declining estrogen accelerates sarcopenia, the age-related loss of muscle mass and function, through several pathways: reduced satellite cell activity, altered protein synthesis signalling, and shifts in fat distribution that can mask muscle loss on the scale even when body weight holds steady. The result is that women in their forties and fifties are losing lean mass faster than the scale suggests, and the anabolic response to a given amount of protein is blunted, mirroring the anabolic resistance seen in older men.

For women in perimenopause or postmenopause who are also managing weight, the adjusted-weight approach is not a minor refinement. It is the correct approach, and targeting the upper end of the 1.3 to 1.5 g/kg range is reasonable. Pairing adequate protein with resistance training amplifies the muscle-retention effect. Mechanical stimulus and sufficient amino acid availability together are more effective than either alone. Resistance training also helps offset the bone density changes that come with declining estrogen. Protein alone is not enough, and exercise without enough protein falls short too.

When to go higher

The upper bound of 1.5 g/kg of target weight is right for most adults in a standard weight-loss phase. Going higher, toward 1.6 g/kg or beyond, is defensible, but only under one condition: consistent resistance training. Above 1.5 g/kg, the main driver of extra protein utilisation is muscle protein synthesis stimulated by mechanical loading. Without that stimulus, additional protein delivers diminishing returns for lean mass retention and adds caloric load that is not warranted.

If you are doing structured strength training two to four times per week, the upper range of 1.5 to 1.6 g/kg of target weight is a reasonable ceiling. If you are not, stay in the 1.3 to 1.5 g/kg range and consider adding resistance training before pushing protein higher. The training stimulus and the protein supply work together. Chasing one without the other is inefficient.

When not to apply this approach: Severe kidney insufficiency (eGFR below 30 ml/min/1.73 m²) changes protein metabolism fundamentally. Do not use the ranges described here. Any diagnosed chronic kidney disease at any stage warrants a conversation with your physician before making significant changes to protein intake. A history of gout or active hyperuricemia calls for monitoring and a preference for lean protein sources. Liver cirrhosis with hepatic encephalopathy operates under different nutritional rules. If you are on SGLT-2 inhibitors, GLP-1 agonists, or sulfonylureas combined with an aggressive caloric deficit, coordinate with your prescriber before significantly increasing protein. The interaction between aggressive energy restriction and these medications carries hypoglycemia risk. If you have a chronic condition or are on regular medication, discuss major dietary changes with a physician before making them.

The bottom line

The protein arithmetic most people use is not wrong in spirit. Eating more protein during weight loss is well-supported. The problem is the denominator. For any adult carrying excess fat, calculating protein from actual body weight inflates the target with tissue that has almost no protein requirement. The corrected approach — target or adjusted weight, 1.3 to 1.5 g/kg, with an upward adjustment for those doing regular resistance training — is both better supported by the evidence and easier to hit in practice.

For adults 40 and over, and especially for women in perimenopause and menopause, getting this right is not an academic exercise. Muscle mass built and maintained in your forties and fifties is one of the strongest predictors of functional independence and metabolic health in the decades that follow. The number you start from matters.

Vitanzo tracks your nutrition entries alongside your activity, sleep, and recovery data, so you can see how your protein intake relates to the rest of your health picture over time, not just on any given day.

References

  • Deutsche Gesellschaft für Ernährung. Referenzwerte Protein. dge.de
  • EFSA. Dietary Reference Values for Protein (Population Reference Intake: 0.83 g/kg/day). efsa.europa.eu
  • Bauer J, et al. Evidence-Based Recommendations for Optimal Dietary Protein Intake in Older People: A Position Paper From the PROT-AGE Study Group. J Am Med Dir Assoc. 2013. PubMed
  • Deutz NE, et al. Protein intake and exercise for optimal muscle function with aging. Clin Nutr. 2014. PubMed
  • Leidy HJ, et al. The role of protein in weight loss and maintenance. Am J Clin Nutr. 2015. PubMed
  • Wycherley TP, et al. Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012. PubMed
  • Evans EM, et al. Effects of protein intake and gender on body composition changes: a randomized clinical weight loss trial. Nutr Metab. 2012. PubMed
  • Weijs PJM, Wolfe RR. Exploration of the protein requirement during weight loss in obese older adults. Clin Nutr. 2016. PubMed
  • Kokura Y, et al. Enhanced protein intake on maintaining muscle mass, strength, and physical function in adults with overweight/obesity: A systematic review and meta-analysis. Clin Nutr ESPEN. 2024. PubMed
  • Weijs PJM. Protein requirement in obesity. Curr Opin Clin Nutr Metab Care. 2025. PubMed