This comment is fascinating.
"Ever see an over-weight or obese person in POW or concentration camp photos and videos?
Apparently, genetics and other fat-factors don't work there."
It's obviously ignorance about basic human biology and genetics. It ignores the fact that genes in this case cause a predisposition, and is not deterministic. Having genes that predispose someone to becoming obese still needs food intake with a lot of calories. This is called a gene(s) - environment interaction.
But because this is not the place for lectures on human biology and genetics I won't go any deeper in the details about that. This is about fallacious reasoning.
The argument given seems to argue that obesity is not genetic because fat people are not seen in concentration camps or in a POW. However, because of the lack of any other context of the discussion I can't do justice to the argument though.
Well for fun let me reconstruct the argument in a basic syllogistic form, which in this is in modes tollens.
P1. IF Genes (and other fat-factors?) cause obesity
THEN People with these genes are always obese
P2. On pictures of a concentration camp or in a POW people are never seen that are Obese or over-weight.
C. Therefore, Genetics (and other fat factors) don't cause obesity.
This translates to;
P1. IF A
P2. NOT B.
C. THEREFORE, NOT A
In this case premise 2 is false and thus the conclusion does not follow from the premises. Which is a non sequitur.
But because I have not seen the discussion I am likely making a straw man of this argument.
But without writing it in syllogism the argument is still fallacious.
The analogy with people in a POW or concentration camp is a very extreme case and is therefore a false analogy
because anyone, no matter their genes, can be starved. Also using the POW and concentration camp as an example is very emotionally loaded, so I would also call this an appeal to emotion
And lastly because I get the sense that this person does not understand how genes could in one case influence obesity and in the other case still can the same case the person could still be starved, this could also be an argument from incredulity
.false analogyhttps://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/181/Weak-Analogyappeal to emotionhttps://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/29/Appeal-to-Emotionargument from incredulityhttps://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/196/Argument-from-Incredulity