Chowing down on a high-fat diet may not only grow your waistline. It may also plump stem cell populations in your gut—cells that are prone to producing tumors.
This study shows that there are more stem cells available in the gut when fed a high fat diet. To jump from evidence of greater stem cell abundance/activity straight to cancer is what most would call “Story Time”. Story time is when researchers start to speculate wildly and pretty much divorce themselves from the data whenever it suits them. Great for brainstorming new things to research, but it should never be the basis of entire news articles for the layperson who cannot differentiate between pure speculation and what the evidence actually says.
An alternate explanation (and one I personally feel to be more in line with basic biology) is that the high fat diet is overall less stressful on the gut, thereby sparing stem cells from having to repair as much damage day-to-day, and thus resulting in greater available un-utilized stem cells for these researchers to detect and manipulate. The metabolism of the intestine is fueled primarily by the catabolism of carbohydrates and carbohydrate precursors like amino acids. Fat largely bypasses the enterocyte to enter the lymph system (the degree to which this happens depends on fatty acid chain length in most species, so the point raised by others regarding the type of fat is very important) to be metabolized first not by the gut but by the liver. Higher fat diets mean lower carbohydrate and/or protein (protein being made of amino acids, many of which can be used to synthesize carbohydrates when catabolized), and as we all know higher carbohydrate diets have been tenuously linked with all sorts of pro-oxidation metabolites and indices of poor gut health like inflammation. Things that would require a higher level of chronic stem cell utilization for repair of oxidation caused damage. This paper is more evidence of the protective effects of fat specifically on gut health, than any evidence of harm from cancer or otherwise.
Never mind the fact that this is ultimately a rodent and cell culture study. Just yesterday ARS had an article showing just why mouse model work is next to worthless as a direct extrapolation to human medicine. From that article
One of the women in the study had complete loss of function from a gene called PRDM-9, which determines where maternal and paternal chromosomes recombine (exchange genetic material) during meiosis. As far as genetic fitness of a species is concerned, this recombination is probably the single best thing about reproducing sexually as opposed to any alternative. PRDM-9 knockout mice are sterile, but this woman was not.
Genes drive our biology, and if genes of fundamental importance to mice can be essentially irrelevant to humans, we should be very careful when extrapolating evidence between the species. Even if, for the sake of argument, we assume that the authors preferred narrative is true all it really tells us is that mice should avoid a 60% fat diet, and that it might be worth looking into the effects of a 60% fat diet in humans. But then you would have to reconcile this assertion with indigenous populations like the Inuit mentioned by someone else who consume diets where essentially all of their calories come from fat, or the Masi who (the men anyway) live almost entirely on milk and blood from cattle which is also very low in carbohydrate and thus resulting in a predominance of calories coming from fat.