Large Memory Usage When Accessing .mat File

I'm running MATLAB 2012b on a Windows 7 desktop with 16 GB of RAM. I have a .mat file that is 12.3 MB in size. I run the whos('-file', filename) to examine the contents of the file. Prior to running the command, here is the output of the memory command:

Maximum possible array:     24509 MB (2.570e+10 bytes) *
Memory available for all arrays:     24509 MB (2.570e+10 bytes) *
Memory used by MATLAB:      6421 MB (6.733e+09 bytes)
Physical Memory (RAM):     16310 MB (1.710e+10 bytes)

Here is the output from memory after running the command:

Maximum possible array:     22692 MB (2.379e+10 bytes) *
Memory available for all arrays:     22692 MB (2.379e+10 bytes) *
Memory used by MATLAB:      8215 MB (8.615e+09 bytes)
Physical Memory (RAM):     16310 MB (1.710e+10 bytes)

Why does running whos on a 12.3 MB file use nearly 2000 MB of memory? Is it possible to free that memory?

I see a similar problem when I call open or load for the file. I can clear the variable returned from either command, but the memory is never free'd.

[Matt J]

Can you recreate the file (i.e., load the contents and then resave)? Does the new file behave any differently if you do?

[Mike]

Loading then saving does not seem to help.

I might add that this is one of many files I am trying to process in a script. I load each file, do some processing, then continue. The load and open functions seem to have the same type of behavior as whos. When I load or open a file, the memory is used and never gets free'd. Eventually, the process uses up all the memory on my machine, and MATLAB dies.

[Maximilian Appel]

Same here, R2016b allocates 2.3TB of memory to load a 500mb .mat v7.3 file. So the process is killed and I will not be able to use my simulation results, yippee.