Effect of short-term dietary fat on cell growth in rat gastrointestinal mucosa and pancreas
Here are the diets by weight of ingredients
and here are the relevant weights after four weeks on the diets
I think it's unarguable that the weight gains are only trivially different between the three groups. It becomes clearer when you look at lard in terms of linoleic acid level as opposed to accepting that it is "saturated fat". Modern lard is around 12% linoleic acid. It might have been a little higher or lower in the 1980s depending on how much adulteration with cheap seed oils the manufacture could get away with in those days or what the pigs were fed on 40 years ago. Lets go with 12% to include the splash of corn oil thrown in.
The control diet is reported as 16.8% total calories as fat and both high fat diets as 52% of calories from fat.
That makes the control diet around 9% linoleic acid, the lard diet 12% linoleic acid and the corn oil diet around 28%.
At 9% LA the control diet is already obesogenic. The lard diet is a bit worse but not in a different ball park, much as I would expect. The fascinating one is the lack of excess weight in the corn oil group, the group with the diet used by the Cairo study as their obesogenic one.
The easy part is to assume that all of the diets in the Jacobs paper are obesogeic, as is the corn oil diet used in the Cairo study. All of these rats gained about 150-180g. The control diet in Cairo was unspecified chow. If it contained 4% or less of linoleic acid we have a plausible explanation for the low weight gain in that control group. We just have to explain why the rats in Jacobs' paper on 12% LA weighed about the same as those on 28% LA.
This is very important to me. There are a series of papers using very high LA diets, especially Safflower oil based, which show minimal obesogenic effects and even the ability to partially reverse lard derived obesity. Something I have been thinking about for years.