How Does Diet Affect The Blood Cell Count?

My doctor recommended an additional blood lab. High iron and low white blood count. Question is not what the cause could be per se, but how much of an impact does diet and exercise have to do with this? I have been busier since end of November until now. Typically I worked-out twice a week+, but since November 2016, almost non-existent and I haven t been eating well (not a lean diet). Just curious prior to my next blood test.