Why we built this
Walk into any gym, open any fitness app, or run any online calculator and you'll find the same thing: tools built around the assumptions of a 25-year-old's body. The standard formulas use the same protein targets, the same activity multipliers, and the same macro ratios for everyone.
That's a problem, because the body you have at 45 is not the body you had at 25. Hormones shift. Muscle becomes harder to build and easier to lose. The way your body processes lipids, alcohol, and even caffeine changes around age 44, and changes again around 60.
Over40Macros exists to fix that gap. Every calculation, recommendation and explanation on this site is grounded in current peer-reviewed research on how human metabolism, body composition and protein needs change after 40.
Who's behind this
I'm not a dietitian or a doctor. I'm someone over 40 who got tired of fitness advice built for 25-year-olds and decided to find out what the peer-reviewed research actually says.
I kept hitting the same wall: generic calculators using outdated formulas, fitness content built on opinion dressed up as fact, and no honest conversation about what genuinely changes in your body after 40. So I went looking for the real answers by reading the studies, checking the citations, and building the tools I wished had existed when I started.
Everything on this site comes from published, peer-reviewed research that you can check yourself. I'm not here to tell you what to do. I'm here to share what the science actually says and make it simple enough to use. Whether that helps you lose fat, keep muscle or just understand what's happening in your body after 40, that's the point of all of it.
What makes this calculator different
- Higher protein targets. We default to 1.6g per kg of body weight, which is within the evidence-based range research recommends for adults over 40, rather than the outdated 0.8g/kg standard.
- Realistic deficits. Aggressive crash dieting accelerates muscle loss, which is exactly the opposite of what you want after 40. We use a moderate 20% deficit for fat loss and 10% surplus for muscle gain.
- Honest about activity. Most calculators encourage you to overestimate your activity level. Our descriptions are deliberately conservative.
- Science-backed explanations. Every claim we make on this site is linked to a peer-reviewed source so you can verify it yourself.
We don't sell supplements. We don't push affiliate links. The calculator is completely free, no sign-up, no email, no catch. Your macro numbers are yours the moment you hit calculate.
If you want the optional extras, all 21 printable meal plans, the personalised macro tracker, the 160+ food guide spreadsheet, and the Over 40 Nutrition Starter Guide, you can grab those free by email. But you never have to. The core tools work without any of it.
The science we rely on
The calculations and recommendations on this site are based on:
- The Mifflin-St Jeor equation, the most accurate validated formula for estimating basal metabolic rate in modern adults
- Research on sarcopenia (age-related muscle loss) from PubMed Central, the Cleveland Clinic, and Harvard Health
- The 2024 Stanford Medicine study published in Nature Aging on the biological shifts that occur in our 40s and 60s
- Peer-reviewed studies in Frontiers in Nutrition and Science on protein requirements and energy expenditure across the lifespan
Full citations are linked at the bottom of the calculator page.
Important honest disclosures
This site is supported by advertising (Google AdSense) so the calculator can stay free for everyone. We do not collect, store, or sell any of the data you enter into the calculator, all calculations happen in your browser and disappear the moment you close the tab.
We are not doctors, dietitians, or medical professionals. The information on this site is general in nature and is not a substitute for personalised medical advice. If you have any health condition, including diabetes, heart disease, kidney issues, or eating disorder history, please consult a qualified healthcare provider before changing your diet.
Get in touch
Questions, feedback, or a research paper you think we should cite? Reach us via the contact page.
Ready to see where you stand?
Two places to start, both free, both under a minute.
Find your macro targets, protein, calories and carbs built specifically for your age, weight and goals.
Or start with something that surprises most people, how old your body actually is, not just your birth certificate.
Use the Macro and Bioligical Age Calculator