Some links on this site are affiliate links. If you purchase through them, we may earn a small commission at no extra cost to you. We only recommend products we believe in.
The standard advice for men who want to get stronger, leaner, and perform better is remarkably consistent. Lift heavy, eat enough protein, sleep eight hours, manage stress. That advice isn't wrong. The problem is that it treats every man's biology as interchangeable, and it isn't.
Two men follow an identical training programme for six months. One adds 8kg of muscle. The other adds 2kg and wonders what he's doing wrong. The training was the same. The nutrition was the same. The effort was the same. What was different? Their genes.
Genetic variation in training response is real and well-documented. A 2007 study in the Journal of Applied Physiology tracked 585 adults through 12 weeks of identical resistance training. The variability in muscle strength gains was enormous — from almost no change to gains exceeding 250% — and a significant portion of that variability was heritable. Generic programmes aren't designed to account for this. FitnessGenes is.
I've been training consistently for fifteen years and I still can't tell you whether I'm a natural responder to volume training or intensity training. I just do what the programme says. Testing with FitnessGenes was the first time I had actual data to anchor that question to.
What FitnessGenes actually tests
FitnessGenes sits in a different category to services like AlphaBiolabs or standard health screening panels. Those services are primarily focused on disease risk and ancestry. FitnessGenes is focused on performance phenotypes — specifically how your genetics influence the way your body responds to exercise and nutrition.
The service analyses over 40 genetic variants across four core domains:
Training response genes — how your muscles adapt to different types of exercise stimulus, your recovery speed, and your injury risk profile.
Nutrition and metabolism genes — how you process carbohydrates, fats, and specific micronutrients, and how your satiety signals work.
Body composition genes — your natural lean mass potential, fat storage patterns, and metabolic rate variation.
Recovery and sleep genes — your cortisol clearance, sleep architecture tendencies, and inflammation response after exercise.
The DNA sample is collected via a simple cheek swab. You register the kit online, post it back, and results arrive within the platform in roughly three to four weeks.
The genes that matter most — and what they mean
ACTN3 — muscle fibre type
ACTN3 codes for alpha-actinin-3, a protein expressed almost exclusively in fast-twitch muscle fibres. The R577X variant determines whether you actually produce this protein. Men with the RR genotype produce it normally and tend to have a higher proportion of fast-twitch fibres — better suited to power and strength work. Men with the XX genotype produce no functional alpha-actinin-3 and skew towards endurance physiology.
This has practical implications for programming. RR men typically respond better to lower-rep, higher-intensity strength work. XX men often respond better to moderate rep ranges with more volume. Neither is superior — they're different physiological profiles that respond to different stimuli.
PPARGC1A — endurance adaptation
PPARGC1A codes for PGC-1 alpha, a transcription factor that acts as a master regulator of mitochondrial biogenesis. Men with the Gly482Ser variant have reduced mitochondrial adaptation in response to endurance training. This affects how quickly cardiovascular fitness improves and how much Zone 2 training volume you need to see meaningful adaptations.
If you've read anything about Zone 2 training for men over 40, you'll know that mitochondrial density is central to long-term health and performance. Your PPARGC1A genotype directly influences how responsive you are to that work.
VDR — vitamin D utilisation
The vitamin D receptor gene (VDR) determines how efficiently your cells respond to vitamin D. The FokI polymorphism produces either a longer or shorter VDR protein, with the shorter f allele associated with greater receptor activity. Ff and ff genotypes absorb and utilise vitamin D more efficiently. FF homozygotes often need higher supplementation doses to achieve the same intracellular effect.
This matters because vitamin D deficiency is strongly associated with lower testosterone. A 2011 randomised controlled trial found that men supplementing with 3,332 IU vitamin D daily for 12 months saw significant increases in total testosterone compared to placebo. Your VDR genotype helps determine your personal dose threshold.
MTHFR — folate metabolism
The MTHFR gene codes for the enzyme that converts folate into its active form (5-methyltetrahydrofolate). The C677T variant reduces enzyme activity — moderately in CT carriers, substantially in TT homozygotes. Men with reduced MTHFR function often need methylated folate rather than standard folic acid, and may have elevated homocysteine if their diet doesn't compensate.
Elevated homocysteine is an independent cardiovascular risk factor and is also linked to lower testosterone production. Knowing your MTHFR status helps you choose the right supplementation approach rather than guessing.
How the platform works
Once your results are processed, FitnessGenes presents them through a web-based dashboard. Each genetic variant is explained in plain English with the mechanism, the implication for you specifically, and a protocol recommendation.
The platform generates a personalised training plan based on your combined genetic profile — not just individual genes in isolation. So if you're ACTN3 RR (power-dominant) but also have a reduced PPARGC1A response, the programme balances strength-focused work with enough endurance stimulus to maintain cardiovascular adaptations.
The nutrition output covers macronutrient ratios, specific micronutrient priorities, and meal timing guidance. If your carbohydrate metabolism genes suggest reduced insulin sensitivity, the plan will steer you towards strategies that support glucose disposal. If your fat oxidation genetics are favourable, it may lean into lower-carbohydrate protocols.
The platform also includes a food diary and exercise tracker so you can sync lifestyle data alongside the genetic baseline. This is where FitnessGenes has a genuine edge over static DNA reports — the protocols are designed to be adjusted as your training data accumulates.
What the output actually looks like
This is where I want to be specific, because the difference between a useful DNA service and an expensive novelty is almost entirely in the output quality.
FitnessGenes gives you a written explanation of each gene, your genotype, and what it means in practice. Crucially, it explains the mechanism — not just "your gene suggests you should eat fewer carbs" but why, specifically, your carbohydrate metabolism gene variant leads to that recommendation. That mechanistic transparency is what separates a credible service from an astrology reading with a lab coat on.
The training plans are periodised, progressive, and specific. They're not generic templates with your name on them. The rep ranges, rest periods, and exercise selection shift based on your genotype profile in ways you can actually verify against the research.
The honest limitations
Genetics explain a portion of individual variation. Not all of it.
Your ACTN3 genotype gives you a starting distribution of muscle fibre types, but training can shift that distribution. Years of high-intensity interval training will recruit and develop fast-twitch fibres even in XX genotype men. Lifestyle factors — sleep, nutrition, stress, training consistency — account for far more of your performance outcome than any single genetic variant.
If you're still in the early years of training, FitnessGenes will tell you things that don't yet matter. Genetic optimisation is a second-order priority. If you're not sleeping, not eating enough protein, and not training consistently, the ACTN3 result is interesting but not actionable. Fix the fundamentals first.
The other limitation is that genetics-based personalisation is probabilistic, not deterministic. The research on gene-exercise interactions is real and growing, but most effect sizes are moderate. Your genetics shift the odds; they don't write the outcome.
FitnessGenes gives you signal about your individual biology that generic programming simply ignores. The gene-based protocols are grounded in real research. The limitation to be honest about is that genetic predisposition is not destiny — lifestyle factors dominate short-term outcomes.
You can learn more about how genetic predisposition interacts with hormonal health in our guide to genetic testosterone predisposition in men.
Who FitnessGenes is actually worth it for
The ideal FitnessGenes customer has been training consistently for at least three years, understands the basics of programming and nutrition, and has hit a genuine plateau. Not "I've been training for three months and I'm not where I want to be." A real plateau where you've optimised the obvious variables and still aren't moving.
Men over 35 get the most value here. Hormonal changes, shifts in recovery capacity, and changes in fat distribution that appear in the mid-thirties are all influenced by genetic factors that FitnessGenes tests for. If you're pairing FitnessGenes data with regular biomarker monitoring, you're operating at a level of self-knowledge that most men never reach.
It's also genuinely useful for men who want to fine-tune nutrition precision. If you've been eating by general guidelines and wondering why your body composition isn't responding the way you expect, carbohydrate metabolism and fat oxidation genetics can point you towards a more specific approach.
If you're a casual exerciser looking for motivation, FitnessGenes is probably more service than you need. The value scales with how seriously you're willing to act on the output.
If you're building a complete self-optimisation picture, FitnessGenes fits alongside bloodwork rather than replacing it. The DNA tells you your baseline tendencies. Regular blood testing tells you whether your lifestyle is compensating for or compounding those tendencies. I've covered how to read your testosterone blood test results separately — that's the other half of the picture.
For men who've done the work to understand their own supplement bioavailability and are ready to push personalisation further, FitnessGenes is the logical next step.
Seb recommends · affiliate link
UK's largest online pharmacy. Prescriptions, advice and more.
Seb recommends · affiliate link
Online prescriptions delivered to your door.
