True.
This is a recognised medical condition.
The 'fishy' smell is caused by a chemical called Trimethylamine (TMA) that is naturally produced by the human body.
Some people lack the enzyme that causes Trimethylamine to be converted to the non-smelly Trimethylamine N-oxide, a condition called Trimethylaminuria, and they have the classic 'fishy' odour.
As an aside, I used to have a job where we used hundreds of Kg's of TMA in the process. No matter how careful you were, and despite all the controls in place, you always had a fishy smell for a few hours after making the addition.
We used to joke that they had a dairy type arrangement milking the TMA from people for our raw material.