A dispute about the effects of a hormone illustrates the
uncertainty and controversy that surrounds scientific
Many groups are searching for molecules involved in metabolic
processes affecting body weight, with a view to developing new
In 2002, a London lab headed by Professor Steve Bloom caused
much excitement when they reported in the journal 'Nature' that a
molecule called PYY3-36 made rats less hungry; they ate less and
got thinner. The molecule even seemed to work on people, in a small
Unfortunately, other labs said they couldn't get the same
results. For any scientific study to be widely accepted, it needs
to be reviewed by experts, published in a scientific journal, and
the results confirmed by different labs. Yet several labs around
the world found they couldn't replicate the findings.
What was going on? Two labs may get different results for a
variety of reasons. For instance, like following a recipe from two
slightly different cookbooks, the labs may follow slightly
different methods. Or like two different chefs, some scientists
will be better at certain experiments than others. Or lab
conditions might be slightly different, or the 'ingredients' (the
reagents) might differ. Very occasionally - and there is not
the slightest suspicion that this is the case here - the lack
of replicability is evidence of scientific fraud.
Things reached a head when a scientist called Matthias Tschöp
got together with other labs to say publicly that they couldn't
repeat Bloom's results. Tschöp and the others had used the same
rats, the same rat food given at the same time of day, and the same
PYY3-36, but still couldn't get the same results.
Bloom suggested the other groups were not doing the experiments
properly, handling the rats in a different way. Things got more
complicated when the drug company that planned to sell a drug based
on PYY3-36 said they could repeat Bloom's results. And in November
2004, two groups announced they could get PYY3-36 to affect
appetite, in rats and rhesus monkeys.
The episode illustrates that science is not cut and dried. At
its leading edge, there is controversy and disagreement, different
theories and models. Over time, as more experiments are carried
out, published and scrutinised, a consensus emerges and (usually)
everyone moves on.