Yes, because you will use all 4 bytes to represent the number.
For example, following the writing order of the bits from right to left, this is how you write the following values as 4-byte integers:
0: 00000000 00000000 00000000 00000000
1: 00000000 00000000 00000000 00000001
128: 00000000 00000000 0000000 10000000
1025: 00000000 0000000 00000100 00000001
etc., etc. up to the highest possible value. Depending on the implementation (and unfortunately I do not know MySql), the bit farthest from the first indicates a signal rather than a value (ie: 0 indicates +, 1 indicates - or vice versa).
This may seem like a waste of space. But there are several reasons why it should be done that way. I'll cite only what I consider stronger: if the number of bytes in the numbers were variable, you would have to interpret a sequence of variable length to know the actual value of the number. For example, if the quantity were variable, and I read the following byte:
00010000
How would I know if the value is 16, or some larger value added to 16? It would have to read another byte, and another, and another, always testing for some stop sign.
But if you are sure that all of your integers have a fixed amount of bytes, you can get that fixed amount of data from the disk first and read it later.
In general, reading multiple bytes at a time from a device such as a disk, flash memory, and even RAM is much faster than reading the same amount of bytes with more than one read operation. So at the end of the day, the loss of space is justified by gaining speed and simplifying the reading.
