Re: How does the fat layer under the skin keep us warm?

Dear Dee,

I encourage you to keep asking questions about your reading.  Many times 
books will suggest areas for questions that may not be covered in the 
text.  Keep up the good work!

Fat is the way people, and animals, store some of the extra food they have 
eaten.  Because the fat does not have another routine job, like the 
muscles and bones do, the fat deposits do not have very many blood vessels 
in them.  Anything that slows down the heat escaping from your body helps 
keep you warm.  That is why you wear more clothes when it is cold 
outside.  Clothes slow down the heat loss from your body to the air around 
you.  Your fat layers perform the same work because of the low blood flow 
through them.  The fat keeps some of your blood from getting too close to 
the skin where it can quickly lose heat.  The result is almost like 
carrying a blanket around with you under your skin.  One large, thick 
layer of fat is just under the layers of muscle across your abdomen 
(stomach area).  There are a lot of blood vessels in your abdomen 
associated with your intestines and other internal organs.  This fat 
layer, called the greater omentum, is a very good use of body fat to 
preserve body heat.

People whose ancestors developed in cold climates (like the Eskimos of the 
Arctic), have more body fat and the fat is distributed over much of their 
bodies uniformly.  This protects more of their bodies from heat loss.  
People whose ancestors developed in hot climates (like the African 
natives), have fat deposits in more localized parts of their bodies, 
leaving large areas of skin with many blood vessels near the skin.  This 
allows these people to cool off more quickly if they become overheated.

You also asked if there are any other ways fat helps keep us warm.  Fat is 
the most concentrated source of energy of the three basic food types (fat 
9 calories per gram, protein 4 calories per gram, and carbohydrates 4 
calories per gram).  Your body burns some of your stored fat when you have 
not eaten enough food to supply all of your body's needs.  So, not only 
does a fat layer help keep you warm by preventing heat loss to the air but 
it is one of the primary fuels that your body burns to produce the heat in 
the first place!

I hope this helps.