For German Shephard dog..How to make her fat and healthy?

I am having a 2 year old pure black double coated female German Shephard d..og..my concern is that she has become lean for the last few months as i was in abroad and concern-person did't fed her properly in last few months..i become shocked to see her as i returned home.Now .any dog lover /dog expert plz suggest me how to bring her in its old shape i mean how to make her fatty ,healthy and shiny again..in quick span of time i am so worried of her..as she is not what she used to be in terms of health and shiny hair etc..short tips are highly appreciated..no funny tips..plz. NOTE--> Fat in terms of stout and strong