The internet's favourite game: is he natural? People scroll Instagram, see someone muscular, and declare with certainty: "100% on gear" or "Natty for sure." Both are usually wrong.
Here's the honest answer: you can't tell from a photo. What you can do is understand the realistic limits of human muscle building and identify extreme outliers. The science is clear. Most of what people think they know is guesswork.
The FFMI: The Only Objective Measure We Have
The Fat-Free Mass Index (FFMI) is the closest thing to an objective measure of unnaturalness. It's not perfect, but it's better than aesthetic guessing.
FFMI is calculated as:
FFMI = (Body weight in kg × (1 − body fat %)) / (height in m)²
Kouri et al. (1995) studied competitive bodybuilders and non-users. Their findings:
- FFMI under 21: Easily achievable naturally. Anyone saying they can't do this without steroids is lying.
- FFMI 21–25: Possible naturally, but requires years of training, good genetics, and optimal nutrition. The upper range (24–25) is rare in documented natural lifters.
- FFMI over 25: Extremely rare in natural athletes. This is the threshold where anabolic steroid use becomes the most parsimonious explanation.
For context, an 80kg man at 12% body fat has an FFMI of 24.8—he's very lean and very muscular. An 85kg man at 15% body fat has an FFMI of 25.4—slightly above the natural ceiling, but not by much.
The problem: most people claiming to be natural and posting physiques haven't measured body fat accurately. They guess. A man saying he's "12% body fat" is usually 14–16%. That changes the FFMI calculation significantly.
The FFMI Limitations
FFMI assumes all muscle is equal. It doesn't account for:
- Frame size and limb length. Taller men have more skeletal height over which to distribute muscle, lowering FFMI. A 6'3" man with an FFMI of 25 is more impressive than a 5'7" man at FFMI 25.
- Genetic outliers. There are people with exceptional androgen receptor density, myostatin mutations, and genetic muscle-building capacity. They're rare, but they exist. Someone with FFMI 26 exists naturally—they're the exception, not the rule.
- Age and training history. A 40-year-old with FFMI 23 after 20 years of training is naturally possible. A 22-year-old with FFMI 23 after 2 years of training is suspicious.
The FFMI is a useful screening tool, not a verdict. FFMI > 25 should raise your eyebrow, not end the discussion.
What Drug Users Actually Look Like
If FFMI doesn't tell the full story, what does?
Simultaneous Extreme Leanness and Muscularity
The biggest tell: a man who is profoundly lean (under 8% body fat) AND profoundly muscular (FFMI > 25) simultaneously. This is nearly impossible naturally.
Here's why: building muscle requires a calorie surplus and muscle protein synthesis. Being extremely lean requires a calorie deficit. Doing both at once (body recomposition) is theoretically possible but glacially slow—it takes years.
Someone who maintains 6% body fat year-round while gaining muscle every month is almost certainly using anabolic compounds. Their synthetic testosterone is overriding the natural signals that make these two states antagonistic.
Skin Condition and Collagen Changes
Anabolic steroid use, especially at high doses, damages skin collagen and causes:
- Severe acne (often on the back and shoulders, not just face)
- Orangepeel texture on the skin (hyperkeratosis)
- Pronounced vascularity even when not training (high hematocrit from steroids)
- Premature skin aging and sun damage appearance
One or two of these aren't diagnostic. Many young, natural lifters have acne. But a 28-year-old with severe acne, papery skin, and extreme vascularity at rest? The pattern starts to point in a direction.
Development of Androgen-Sensitive Tissues
Anabolic steroids increase androgen receptor activation everywhere—including tissues where extra muscle isn't desirable:
- Deltoids and traps: These muscles have high androgen receptor density. They blow up dramatically on steroids. A lifter with massive delts relative to pecs/lats is suggestive.
- Head size: Jaw widening and nose thickening occur from growth hormone use (acromegaly-lite). You can't miss this in someone who competed naturally 5 years ago.
- Neck thickness: Extreme neck and trap development relative to chest development is another androgen-sensitive pattern.
None of these alone are diagnostic. But a pattern—massive delts, huge traps, widened jaw, severe acne, extreme vascularity—paints a picture.
Rate of Muscle Gain
A natural lifter gains 0.5–1kg of muscle per month in their first year of training. By year three, this drops to 0.25kg per month. By year five, muscle gain is minimal without a significant calorie surplus (and then much of it is fat).
Someone gaining 2kg of muscle per month year-round is almost certainly using exogenous hormones. The human body doesn't work that fast naturally.
What You CANNOT Tell From Looking
This is important: you cannot tell if someone is natural based on muscularity alone.
A natural lifter with exceptional genetics, 10 years of training, and perfect nutrition can build an FFMI of 24–25. They'll look extremely impressive—magazine cover material. They might look identical to someone on 300mg of testosterone weekly.
This is why the "natty or not" game on Instagram is useless. You're looking at a photo. You don't know:
- Training age (someone could be year 15 of training)
- Genetic potential
- Actual body fat percentage (they're probably lower than they claim)
- Anabolic window (one photo at peak pump, peak lighting, and peak tan)
- History (they might have cycled off and are now at a natural maintenance)
The WADA Tested vs Untested Distinction
Professional tested competitions (WADA, tested federations) provide some assurance. Athletes are drug-tested. It's not foolproof—methods exist to pass tests—but it's better than nothing.
Untested competitions (bodybuilding, some powerlifting federations) have zero barrier to entry. Someone can walk on stage after 12 weeks of heavy steroid use. The "natural" division is often just bodybuilding for people who don't want to admit they're using.
This is worth knowing: many people claiming natty status are competing in untested federations where "natty" is a marketing category, not a reality.
The Honest Framework
Here's how to think about "natty or not":
Probably natural:
- FFMI under 23
- Training age > 5 years
- No extreme combination of leanness + muscularity
- No obvious androgen-sensitive tissue overgrowth
- Ages 16–25 with < 2 years training is unlikely to be massive and shredded
Suspicious (doesn't mean they're using, means it's worth questioning):
- FFMI 24–26
- Simultaneous extreme leanness (under 8%) and muscularity
- Recent rapid muscle gain (2kg+ per month, multiple months)
- Obvious skin/collagen damage (severe acne, aging appearance)
- Androgen-sensitive tissue overgrowth (massive delts relative to chest)
Very likely using:
- FFMI > 26
- All of the above combined
- Admitted to use or tracked during testing failure
The Bottom Line
You cannot tell from a photo. FFMI is a useful tool, but it's not a perfect detector. The rare natural outlier exists. The liar claiming natty status will never admit it.
What you can do:
- Understand FFMI and use it as a screening tool, not a verdict
- Recognise that pattern recognition (multiple suspicious signs) is better than single-variable assessment
- Accept that exceptional genetics exist, but are rare
- Know that tested federations provide more assurance than untested ones
- Stop declaring certainty based on Instagram photos
The fitness world runs on ego and marketing. Everyone wants to be special—either naturally gifted or honest about enhancement. Neither is usually true. Most are just normal people, years into training, with good lighting.
The question "natty or not" will always obsess the internet. The honest answer is: you don't know, and neither does anyone else without testing.
References:
Kouri, E. M., Pope Jr, H. G., Oliva, P. S., & Gruber, A. J. (1995). Anabolic-androgenic steroid use by male weightlifters: self-reported effects on sexual function, interest, and behaviour. Archives of Sexual Behaviour, 24(5), 555–571.
See our testosterone optimisation guide for a deeper dive into natural hormone levels and realistic expectations.