I want some advice on manipulating people's bodies?

[Ariel]

I realized looking at pictures where the person I'm editing has a swimsuit on I can easily adjust them to look skinnier or fatter, but when people are wearing clothes, or standing next to others (meaning that there is no background space around them) I can only do a few small adjustments. The only things I've learned to apply are using liquefy and then the push tool in that, and also just using the brush tool to draw the shadows or erase them to add or hide a gut.
Thanks in advance if you read my problem and try to help!

 

[IamSam]

One method you could try is isolating that person or the part of that person from the image.
Always duplicate the original and turn it off. Work on the duplicate.
Select the person or parts of the person using whatever selection method you prefer. I would use the Pen Tool.

EDIT: I did this very fast so its a bit sloppy. This is also not the best image to demonstrate the technique, but it was the first one I came across.

Here's what I want to change.



Copy the selection to it's own layer. We will call it The isolated person layer.



Isolated person layer: Use whatever tool you like to make them skinnier.

It's hard to tell, but I used the liquify Tool to alter the arm (and chest).



Original image: Use the Clone Stamp Tool or the Healing Brush Tool to ready the BG (in the duplicate) for the new skinny person.

Here, using the arrows and a white template (which you won't use), I show where, on the duplicate you must use the Clone Stamp Tool to make up for the deficit.

 

[chrisdesign]

I did an example image for Sam.

 

[ibclare]

I can't remember the tool, but there is one which moves content between figures that might be helpful, but I have never tried it . . . Anybody?