The photoinduced reaction cycle of bacteriorhodopsin has been investigated by transient phase grating experiments. This technique with the probe frequency well off any retinal resonance and thus being solely sensitive to refractive index changes of the sample allows the study of energy dissipation and global density changes in the protein. Within the experimental time window between 1 and 20 ns no significant energy release or structural transition of bacteriorhodopsin has been found. This indicates that on this time scale conformational changes of bacteriorhodopsin are synchronized with the well-known dynamics of the retinal chromophore.