there was a study a while ago which suggested that having the pedal axle under the arch of the foot (ie directly in line with the tibia) gave a better power transfer - but I think overall, the disadvantages outweighed the benefits.
To answer the question - it's impossible to answer, without knowing where your cleats were positioned before and how far you intend on moving them back. However, you will know the first time you get back on the bike.