international management and industrial engineering are the 2 most frequent background for MBB consultants. However, in recent years, lots of different degrees are being considered interesting from top-tiers, e.g. finance, computer science, maths, physics.
My advice is to follow your passion to better perform and enjoy these years, but at the same time develop business culture through books, papers, and articles, and approach the consulting business cases. The must-have on your CV should be:
1. International experiences: internships in multinationals, exchange programs and/or summer schools in top Universities.
2. Strong academic performances.
With these points, you will be invited by MBB (a plus - not needed - can be an entrepreneurial experience).