Background: The production of recombinant proteins for therapeutic use represents a great impact on the biotechnology industry. In this context, established mammalian cell lines, especially CHO cells, have become a standard system for the production of such proteins. Their ability to properly configure and excrete proteins in functional form is an enormous advantage which should be contrasted with their inherent technological limitations. These cell systems exhibit a metabolic behaviour associated with elevated cell proliferation which involves a high consumption of glucose and glutamine, resulting in the rapid depletion of these nutrients in the medium and the accumulation of ammonium and lactate. Both phenomena contribute to the limitation of cell growth, the triggering of apoptotic processes and the loss of quality of the recombinant protein. Results: In this review, the use of alternative substrates and genetic modifications (host cell engineering) are analyzed as tools to overcome those limitations. In general, the results obtained are promising. However, metabolic and physiological phenomena involved in CHO cells are still barely understood. Thus, most of publications are focused on specific modifications rather than giving a systemic perspective. Conclusions: A deeper insight in the integrated understanding of metabolism and cell mechanisms is required in order to define complementary strategies at these two levels, so providing effective means to control nutrients consumption, reduce by-products and increase process productivity.