The gap between how confidently a product is marketed and how well it is evidenced is close to
inverse. The things with hundreds of trials behind them are sold quietly in plain tubs. The things
with none are sold with the most certainty.

Here is a ranking by evidence rather than by enthusiasm.

Tier one: overwhelming evidence

Only a handful of things belong here. creatine is the clear leader — hundreds of human trials,
consistent effects on strength and power, an excellent safety record over decades, and a price that
makes it almost absurd value. If someone takes one supplement, this is the one.

Protein is the other. Not glamorous, not interesting, but the effect on lean mass retention in a
deficit is about as well established as anything in sports nutrition. Caffeine completes the tier.

Tier two: strong clinical evidence, borrowed context

This tier is where prescription medicines sit. The evidence is genuinely strong — but it was
generated for a clinical population, and borrowing it for physique purposes changes the risk
calculation without changing the confidence people feel.

GLP-1 receptor agonists are the obvious example. tirzepatide has produced some of the most
striking weight-loss results in pharmacological history, in properly conducted trials. Those trials
were in people with obesity or type 2 diabetes under medical supervision, which is not the same as a
lean lifter self-administering for a cut.

Insulin-sensitising agents belong here too. People buy metformin on the strength of a very
large evidence base in diabetes and a smaller, more speculative one around longevity. Thyroid hormone
sits in the same bracket — cytomel and its equivalents unquestionably raise metabolic rate,
because that is what thyroid hormone does. The trials establishing that were in hypothyroid patients.

Tier three: real but modest

yohimbine has genuine human data for fat mobilisation, particularly in a fasted state, alongside
a well-documented tendency to raise blood pressure and provoke anxiety. It works, mildly, with a cost.

Stimulant thermogenics belong here. Anyone buying ephedrine tablets is purchasing something with
demonstrated effect on energy expenditure and appetite, and a cardiovascular profile that got it
restricted in several markets. The effect is real; so is the reason for the restriction.

Glutamine is a curiosity in this tier — a genuinely important amino acid with a large body of
clinical research in critical illness, and very little to show for it in healthy trained people.
l glutamine uk searches usually come from people expecting recovery benefits the trials in
athletes have not found.

Tier four: plausible mechanism, thin human data

Most peptides live here. Growth hormone secretagogues do measurably raise IGF-1, and people
buy ipamorelin on that basis, but the outcome data in healthy adults is thin and the insulin
sensitivity cost is documented. Plausible is not proven.

Selective estrogen receptor modulators used for hormonal restart are better evidenced than most of
this tier — enclomiphene uk products relate to a compound with actual trial data on raising
endogenous testosterone, which is more than can be said for most things sold in the same corner of
the market.

Tier five: cosmetic claims, variable evidence

Topical actives are unusual in having decent dermatological evidence while being sold with wild
claims. hyaluronic acid serum products genuinely hydrate the stratum corneum; they do not, as
frequently implied, restructure the dermis. Retinoids in the same aisle have far stronger evidence and
get a fraction of the marketing.

How to use this ranking

Spend money from the top down. Most people do the opposite — an exotic peptide before they have
sorted protein intake, or a thermogenic before they have established a deficit.

The uncomfortable truth is that tier one plus adequate sleep and a sensible programme accounts for
the overwhelming majority of achievable progress. Everything below tier two is fighting over the
remaining few per cent, at rapidly escalating cost and risk.

Anything in tier two carries prescription status for a reason and warrants a clinician and blood
work. That is not a disclaimer added at the end — it is the actual difference between borrowing
clinical evidence responsibly and borrowing it recklessly.

Information only — not medical advice. Several substances referenced are prescription-only medicines or controlled drugs in the UK; supply is a criminal offence regardless of profit. Anyone considering use should obtain baseline blood work and consult a qualified clinician.