Feed the frog every day.....high protein, low fat. Dust with high quality calcium every third day. Nightcrawlers are the best staple (cheap, highly nutritious, easy to keep). These little guys grow so fast that they need lots of nutrients. Feed everyday as much as it'll eat in fifteen min. Stop worrying about obesity. Unless you are feeding only mammals your frog isn't going to get fat.....BTW, looks female.....way too young to tell, but its not an 'obvious male' so I'll stick with female for now.
In the future for sexing pics: Take one from above, one straight on at eye level, and a profile shot (side) at eye level. The frog needs to be on a flat surface (not in water it distorts) when taking the photo.
One more thing.....why are you taking it out to feed?