A distinction has to be made between, monosaturated, polysaturated and saturated fats which are the natural ones, for the lack of a better word and trans and hydrogenated fats which are man made aberrations that have no place in anyones diet, as far as I'm concerned.
I don't know what are the implications of a high trans fat diet in what concerns muscle building but in general health terms they'll:
Raise your bad cholesterol while lowering the good one
They are incorporated in cell menbranes where they'll alter the way the cell membrane behaviours, which might be particulary harmfull to your brain.
They'll also reduce your blood vessels hability to dilate, a marker in CVD risk.
Increase the risk of developing diabetes , some kinds of cancer and there's probably a ton more I don't know about.
Then there's the omega 3 to 6 ratio and all that...