Question: From further investigations I see that someone came with an idea that gives support to my theory that elves don't have body fat. 

Their idea was that Elves [store their energy as ethanol](https://worldbuilding.stackexchange.com/questions/128909/how-could-elves-survive-without-any-fat-cell-in-their-body/128932#128932) in their blood. 
This idea implies that Elves basically walk around with anti-freeze blood that can protect against infections better than normal blood while also making it so that Elves can't get drunk. 

But another problem arises, people with low body fat tend to look like road maps,cause even if there are small muscles below the skin, if there is 0 fat to cover it then even the smallest muscles are perfectly visible. 
[![enter image description here](https://i.stack.imgur.com/dYuym.jpg)](https://i.stack.imgur.com/dYuym.jpg)

So, How can Elves have 0% body fat and not look like some freaky walking road map?

Answer: 
Elves have thicker skin. Literally.

One of the purposes of fat in the body is kinetic: it serves as a cushion to absorb and distribute the force of impacts - not just in the sense of punches or falling rocks, but also things like the ground impacting your foot as you walk around on it.

Since your elves don't have fat, it follows that some other part of the body has to be cushioning it. The dermis - the middle layer of skin - already provides some cushioning effects, so it makes sense to me that in your elves, it would take on this role, becoming thicker, denser, and stiffer than in humans. Therefore, it would be less inclined to mold itself to the contours of the body beneath. (It would also be less able to expand and contract, which would be a problem in a human since our bodies change shape as we gain and lose fat - but conveniently, elves don't do that.)

The outer layer of skin would be relatively unaffected, so it shouldn't feel any different to the touch. I would expect that facial muscles might have a harder time flexing the thicker skin, hence why elves are often known for their stoicism - their faces are literally less expressive than humans'.

I welcome people who actually know things about anatomy to pick holes in this idea.
Type 1 Muscle Tissue
--------------------

As a species your elves have a predisposition to [Type 1 muscle tissue](https://en.wikipedia.org/wiki/Muscle#Types), which is 'slow twitch'. A normal seditary man or a woman is believed to have 45% Type 2 muscle mass and 55% Type 1. However long distance runners have [higher percentages of Type 1 muscle mass](https://en.wikipedia.org/wiki/Myocyte#Fiber_types).

In this picture you can actually see that Type 1 muscle users have less definition in their exposed areas.
[![muscle fibre types](https://i.stack.imgur.com/nckR0.jpg)](https://i.stack.imgur.com/nckR0.jpg)

This would also help explain why your elves can perform endurance tasks well, [which is a common elvish trope](https://www.planet-tolkien.com/board/5/5125/0/elves-vs-men).