I sometimes briefly watch football games on TV. And I can’t help but notice that some men are skinny. And some have rather more thick bone structure. And more than once this made me wonder.
Are skinny people more predisposed to breaking their bones?
I’ve never heard anything suggesting that they are. And I know the human body often has these inborn tendencies to deal with just such a thing. But to-date I at least have never heard of any kind of research being done on that.
Well 
?
These two sentences next to each other imply a misconception.
While indeed some people have thicker bones than others, it’s barely noticeable visually.
The main difference between skinny and “big boned” people are differences in the size of muscles and quantity of fatty tissue.
“Big-boned” may not just be a euphemism for"fat" - there’s some evidence that obese people have larger femurs in order to bear the extra weight.
But size doesn’t equate to quality of bone.
https://www.endocrineweb.com/news/obesity/20229-being-obese-can-lead-weak-bones
Years ago I did a bit of work with a group looking at osteoporosis and bone fractures. I learnt some interesting and unexpected things about bones.
Bones are remarkable things. The internal structure of spongy bone carries a big part of the load and provides a reinforcing 3D structure. This trabecular structure is constantly renewed by the osteoclasts and osteoblasts and will change in structure and density to meet the forces on the bone. Greater forces and the bone will over time increase in density and strength. It happens slowly,
Increased weight will result in greater bone density of the weight bearing bones.
In osteoporosis the osteoclasts start to outrun the osteoclasts and strip out material from the trabeculae. This is why weight bearing exercise is so important before menopause for women. Get a head start on osteoporosis.
In serious osteoporosis the entire trabecular mesh can be eroded to uselessness. Even drugs that stimulate osteoblasts to lay down material have trouble as the basic geometry they lay down on is gone, so although bone density increases it does so in a much less efficient manner and fracture resistance does not improve nearly as much as one would hope for.
The osteoblasts seem to have a similar sort of trouble when fluoride is added to the mix. In one study, bone density improved substantially with fluoride supplementation but the fracture rate actually increased and didn’t just " not improve nearly as much as one would hope".
https://www.nejm.org/doi/full/10.1056/nejm199003223221203
(This is also a good lesson in clinical medicine for not using surrogate end-points. If you’re interested in fractures measure the fracture rate not the bone density.)