Ellen Kuhfeld wrote:As for feet, I can only suggest they spread out from many years of supporting increasing weight. This might not be a factor for people that lose weight as they age, but I am not one of that fortunate crew.
Kinda.
So... as someone who actually has to have a rather intimate knowledge of growth pathways for everything in the body by this point in my career (med student about to take boards), this is how it works (simplified, since I'm sure you all don't care about all the minutiae):
The bones in the feet grow the same way the others do in your body. The actual length of each bone is determined by a number of factors, genetics being the first and probably most important one assuming that nothing goes wrong. Basically, if everything works properly, genetics determines bone length. The actual mechanism of growth, however, is intimately tied to 3 hormone levels, though others play lesser roles. These hormone levels reflect nutritional status. Being malnourished or overfed both can lead to growth retardation.
Growth Hormone is the primary determining factor for the amount of IGF-1 that your body produces. These 2 hormones play the largest role in actually causing the bones to grow in length. Gigantism, as mentioned earlier on the thread, is when a child has too much growth hormone, causing the bones to grow longer faster than they should.
The sex-hormones, testosterone and estrogen, play 2 major roles in bone growth. First, like GH and IGF-1, they increase the rate at which the length of bones increases. This is why you have a growth spurt in puberty. But, unlike GH and IGF-1, which merely cause the bones to grow, the sex-hormones cause closure of the growth plate within a few years. The earlier you start puberty, the taller you will be for your age group, but the shorter you will be on average because of this.
The bones in the feet and hands, due to just how many of them there are, cause those two areas of the body to enlarge to closer to their maximum size a bit earlier than the rest of the skeleton in many people (though this isn't biologically a fact in general), which makes sense since the feet have to support the weight of the frame of the body, it makes a lot of sense for them to grow faster first and slower later.
Now, by the end of puberty, all linear bone growth is stopped and the final bone lengths are reached. This is true for the feet. They can, however, expand slightly with age and weight gain, but that isn't actually a process of bone growth. As you get heavier you put more strain on the tendons and ligaments that hold the foot bones in place. Much of the expansion you see with age is that these connectors loosen, so the foot naturally spreads out more. Connective tissues can also be laid down to increase the surface are as you get heavier. A final factor, as the heart gets weaker (assuming you are heading towards heart failure) or the kidney starts to fail, you get fluid buildup in the lower extremities, leading to increased foot size.
But... from a sheer growth perspective. By the end of puberty you have reached your final foot size.