The present invention is in the field of hair treatment compositions; in particular relates to a method for hair volume reduction. Despite the prior art, there still exists the opportunity to increase the conditioning benefits delivered through hair treatment compositions. It is therefore an object of the present invention to provide a method that retains shape and reduces frizz even after exposure to humidity and washing the hair. It has been found that reduced hair frizz and hair shape retention even after exposure to moisture can be obtained by using N-formyl amino acids.