Nothing but Skin and Bones - Television Tropes & Idioms

A character is shown as exaggeratedly skinny, usually for any of the following reasons:

A character hasn't eaten anything in a long time (or a short time) and it's just a joke to exaggerate how long they've been starving or how hungry they are.
A character is about to be eaten by a monster or predatory animal and they make themselves look this way so the creature won't want to eat them.
Supermodels and people stranded on Deserted Islands are often depicted this way.

Most often Played for Laughs, this is usually just a short Sight Gag with no relevance on the plot. Plot-relevant examples are much less common, as they're rarely funny.

Sometimes crosses with Lean and Mean.

Examples of incredibly thin characters with no visible bones instead fall under Noodle People.

Examples:

An ad for awareness of Anorexia Nervosa showed a sadly undoctored picture of an emaciated Isabella Caro.

Nagato, a villain of Naruto, is horribly skinny because of a Dangerous Forbidden Technique of his, which drained his energy. His legs were burned useless just before that. And overall, he uses nothing but techniques that consume huge amounts of Chakra. Here is the result.

Literature

In The Quest for Saint Camber, Nigel is described as wasted and frail some two weeks after Conall attacked him with magic and left him in a coma. Since Nigel got no solid food for that period, it's entirely plot justified and not pretty. Morgan and Duncan leave Rhemuth to search for Kelson and Dhugal partly to avoid watching Nigel starve to death.
A Song of Ice and Fire: Theon is (well, was) a tall, good-looking youth. After spending a little vacation time in the Dreadfort, he comes out some three stone lighter both due to muscle atrophy and starvation. That's forty-two pounds or nineteen kilograms for someone who wasn't even least bit overweight to begin with.
Skulduggery Pleasant: Carol describes Crystal as this. It's Played for Drama.

Film

In Se7en one of the serial killer's victims has been reduced to this after a year spent strapped to a bed. The worst part? He's still alive! Morgan Freeman's character speculates that the poor bastard ate his own tongue to sustain himself.

Seen on Intervention either because the person has been consuming mostly drugs and little food, or has an eating disorder.
Subverted in an episode of The Drew Carey Show. Drew is on a hunger strike and when Mr. Wick comes to see him at home, Wick finds Drew lying on the couch due to lack of energy and is now extremely skinny. But it turns out that Drew knew Wick was coming over and he got an assist from a pizza delivery man who is naturally extremely skinny. The pizza guy is willing to help because Drew on a hunger strike is costing him business. They lay on the couch together, covered by a blanket, arranged in a way that it looks like Drew's head is on the other guy's body.

Music

4st 7lb by Manic Street Preachers.
Bleed Like Me by Garbage.
And the kick is so divine when she sees bones beneath her skin.

A short sequence of some early Dilbert strips observed Dilbert's date with a supermodel, who was drawn as a literal skeleton, and did not eat on their dinner date but instead simply sniffed the mints.

In the Forgotten Realms setting, Chosen Ones are humans transformed into humanoid monsters by the Red Wizards of Thay. They are downright morbidly thin◊.

Issue 8 of Flying Suit Reiko has Reiko getting her overweight friend Potchari to take a fitness test for her so she can take diet pills she's inelligible for and throughout the story she gets skinnier and skinnier.
Sinjal/Crippled from Wurr is very, very skinny. While not underfed per se (not anymore than, say, Morri) he has severe disgestion problems.
Slimy Thief: Absorbing water can cause Aisha to swell up but losing water, especially a lot of it, can cause her to shrivel to emaciated state. After a some adventuring and drinking Aisha comes in her fat form but after an extremely long bathroom break, she walks out of the toilet just skin and bones much to Camilia's horror since she is unaware of Aisha's power.

In one Quick Draw McGraw cartoon, a wild mountain lion steals one of Quick-Draw's biggest, fattest sheep, then shears it down to prepare it for dinner. It is then that he discovers that the sheep is rail thin underneath its wool.
In Adventure Time, The Ice King is actually very skinny under his robe. Though sometimes he's very fat, depending on what's funnier or more pathetic.
- In a rare serious example of the trope, "All Your Fault" features two frighteningly gaunt, starving Lemongrabs. *shudder*
In an episode of Ren and Stimpy, the duo are starving and Ren opens his skin to show there's literally no fat, just bone. Then Stimpy opens his skin to show he's nothing but skin and fat.
In the Brandy & Mr. Whiskers episode "Wolfie: Prince of the Jungle" Brandy has a bunch of fashion magazines on the floor. One of them has a literal skeleton on it.
Bugs Bunny and Daffy Duck have been known to show skinnier frames under their skins to try to deter those who wish to eat them.
In the My Little Pony: Friendship Is Magic episode "Hearts and Hooves Day", the Cutie Mark Crusaders have an Imagine Spot where a famine strikes Ponyville and when background pony Lily Valley momentarily stands up right in front of the "camera" she suddenly has protruding ribs and a concave stomach.

The victims of Nazi Germany and other notorious nations throughout history have been found in this condition.
Tuberculosis wasn't known as Consumption for nothing.
A very unfortunate case of Truth in Television, victims of prolonged starvation or illness will really wither away down to a flap of skin over a malnourished skeleton.