I know you have mentioned several times you were not concerned with muscle loss...I'm scratching my head each time I think about this. You do realize that the more lean muscle tissue you have - the more bodyfat you will metabolize as your 'metabolism' is higher due to the higher lean mass ratio to bodyfat. Eating a more well-rounded nutritionally sound breakfast and diet in general is going to be so much healthier.
Not trying to tell you what to think - just speaking about overall health. Protien shake is fine, even though whole food is a better first meal - shake second meal. Take care.