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It’s not that simple. As the article correctly states: > But he said the idea that obesity itself or eating too little fibre "causes" cancer was "somewhat simp
by klmr 9y ago
It’s not that simple. As the article correctly states:
> But he said the idea that obesity itself or eating too little fibre "causes" cancer was "somewhat simplistic" and still needed to be explored further.
Diet is certainly contributing to cancer risk but there’s no simple, direct line from sugar to cancer, or from inactivity to cancer.
For example, one aspect of cancer risk is that it’s simply a game of numbers: obese people have bigger cells (and, at least in the case of children, more cells!). More cells trivially translates into a higher cancer risk because every single cell individually has the potential of becoming a tumour precursor. But even a constant number of bigger cells increases cancer risk by a similar logic: more cellular mass increases the risk of a cell becoming cancerous because there are more molecules that can become abnormal, disrupt cellular processes and ultimately lead to DNA damage.
These are the facts. Whether this noticeably contributes to the increased cancer risk in obese people is an open question. Nevertheless, in this scenario it’s actually the obesity itself, and not the diet/inactivity that acts as a causal factor for cancer.
Ultimately this is probably a tiny contributor. Another comment correctly singles out that obesity causes (chronic) inflammation, which is almost certainly a much bigger single contributor to cancer risk.
- jiggunjer 9y agoBy that overly simplistic statistical reasoning, whales should be riddled with tumors.
- nonbel 9y agoThe parent is wrong in that they fail to distinguish between terminal/differentiated cells and tissue stem cells. Also they imply there is a one-to-one correspondence between the relevant cell divisions and number of total cells at any one time. This is not the case. Eg, you can have one skin stem cell divide once to replace a single terminal cell (one of the daughters remains as a stem cell). Or that one daughter cell can divide itself once to replace two terminal cells per stem cell divisions. Or those two cells can each divide to get 4 terminal cells per stem cell division, etc. The relevant number is divisions since the fertilized egg for each stem cell lineage.
- klmr 9y ago> they fail to distinguish between terminal/differentiated cells and tissue stem cells I don’t distinguish them because what I’ve said is true both for differentiated and stem cells. I’m not saying that there are no relevant differences between these cells, obviously. > they imply there is a one-to-one correspondence between the relevant cell divisions and number of total cells at any one time Uh, where did I imply that? That would obviously be false but, again, it’s not relevant to the argument I’m making. > The relevant number is divisions since the fertilized egg for each stem cell lineage. The relevant number for what? I was talking about the total number/size of cells at a given time, not the number of cell divisions, which is an entirely different (but also relevant) facet of tumourigenesis.
- mrec 9y agoThis is actually an interesting open question, known as Peto's paradox [1]. The "hypertumors" hypothesis is especially fun - a tumor has to get really big to affect something the size of a whale, and a tumor that big needs a fair amount of internal structure to support it, and tumor cells have a demonstrated tendency to misbehave already, so the tumors get cancer of their own and die before they can get big enough to affect the host. [1] https://en.wikipedia.org/wiki/Peto%27s_paradox https://en.wikipedia.org/wiki/Peto%27s_paradox
- klmr 9y agoHm. I had hoped that the caveats I explicitly mentioned would make this the opposite of “overly simplistic”. But, yes: all other things being equal, whales would have a lot more tumours than other, smaller organisms. Now, it should be maddeningly obvious that all other things are not equal. In the end we’re not comparing whales to other species here, we’re comparing between humans.