Do seed oils (linoleic acid) cause obesity? Discussion on this often involves rodent studies. But there are a lot of rodent studies out there and they can be difficult to interpret. So I thought I'd start a thread to look at some of the less cited studies.

If you are going to compare a diet high in linoleic acid you need to compare it to something low in that. Some have used cocoa butter as a comparison but stearic acid isn't well absorbed in mice and rats. Not many people live on cocoa butter either. https://twitter.com/MatthewJDalby/status/1310966867566178307

Beef tallow is another fat very low in linoleic acid that perhaps more resembles the fats people eat.

How does tallow do in mice?

You can do a search on pubmed.

"((((tallow) AND (mice)) AND (diet)) AND ("body weight"))" https://pubmed.ncbi.nlm.nih.gov/?term=%28%28%28%28tallow%29+AND+%28mice%29%29+AND+%28diet%29%29+AND+%28%22body+weight%22%29%29&sort=pubdate&size=100

1983 in the British Journal of Nutrition.

Mice fed lard, beef tallow, sunflower oil or soya-bean
oil.

Tallow mice gained the most weight, sunflower oil the least.
https://pubmed.ncbi.nlm.nih.gov/6821685/ 

1987

Genetically lean or genetically obese mice fed either diet with either corn oil or beef tallow.

Mice of both types gained more weight on beef tallow than corn oil.
https://pubmed.ncbi.nlm.nih.gov/3320290/ 

From 1992 in Japan.

Beef tallow fed mice weighed a bit less and had less body fat than soybean oil, linseed oil, and fish oil.

Hydrogenated tallow fat even more so. Possibly an essential fatty acid deficiency?

2015

Mice fed the beef tallow (BT) diet gained more weight and body fat than the mice eating the corn oil (CO) diet.

(The other groups have microalgal oil supplements)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4700911/

Then there was this 2019 study.

Mice on the beef tallow diet (Beef) gained about the same weight as the mice on the corn oil (Corn) and soy oil diet.
https://www.mdpi.com/2072-6643/11/9/2127/htm#app1-nutrients-11-02127

What about in rats?

"((((tallow) AND (rats)) AND (diet)) AND (body weight))" https://pubmed.ncbi.nlm.nih.gov/?term=%28%28%28%28tallow%29+AND+%28rats%29%29+AND+%28diet%29%29+AND+%28body+weight%29%29&sort=pubdate&size=100

From 1990 in Japan.

Comparing rats fed beef tallow and safflower oil.

"After the experimental period (4 mo), body fat accumulation was significantly less in the rats fed safflower oil."
https://pubmed.ncbi.nlm.nih.gov/2231019/ 

1991

No difference in body weight of rats fed beef tallow or corn oil after 9 months.
https://pubmed.ncbi.nlm.nih.gov/1765820/ 

From 2002.

"Each group of rats showed the same weight gain during the 8-week experimental period. Carcass fat content was greater in rats fed the beef tallow diet than in those fed the with the safflower or soybean oil diets..."
https://pubmed.ncbi.nlm.nih.gov/12495263/ 

2003

No difference between weight gain in rats fed beef tallow (BT) or safflower oil (SO).

" There were no main effects for fat or the interaction of these components with respect to body weight, weight gain, and food intake"
https://pubmed.ncbi.nlm.nih.gov/12562868/ 

Overall beef tallow seems to be equal to or more fattening that linoleic rich seed oils in rats and mice.

There is a lot more potential reading around why we see these effects in rodents.

I'm doubtful they have much relevance to us though or what you should eat. Rats and mice seem to be so much more sensitive to these differences in dietary composition that we are.

But if you are going to use rodent studies as evidence it is worth looking at all of them.