Graham's diet: Fat or no?

In Cecil’s column on Graham crackers, we have the quote

But in the next sentence,

So, was fat allowed, or not, in Graham’s diet?

I rather fancy the obvious ambiguity in the word “fat” is operating here.

Just a WAG, but maybe people in the first half of the 19th century didn’t know how high the fat content in eggs and dairy is. The fat on red meat on the other hand is pretty obvious.

That occurred to me, too, but the diet was vegetarian to start with. You don’t need to specifically exclude animal fat, if you’re already excluding all meat. And they had to know how fatty milk, at least, is, since you make butter from it, and they would know how much butter you could get from a certain amount of whole milk.

Did the definition:

fat The ester of glycerol and one, two, or three fatty acids.

even exist in Graham’s heyday?

Probably not, but I would imagine that they had some other definition of “fat” which was almost equivalent.

And strictly speaking, isn’t it only a fat if it has three fatty acids? The others would then be lipids, but not fats. At least in the eyes of the FDA this seems to be the case: Fat-free “fatty” foods like margarine and mayonnaise often have “mono and diglycerides” as a major ingredient.

Did they? Or did “fat” mean only “the white, greasy part of meat”?

Again, if that’s what they meant by fat, it was already excluded, by excluding all meat, so excluding fat is redundant. Nonetheless, I would imagine that they had noticed that you could fry things in animal fat, or in butter, or in vegetable oils, or the like, and that furthermore, all of those substances had similar taste and mouth feel, and that they all made paper transparent, and had made the connection that all those things were somehow related. Whether they used the name “fat” for the category containing all those things, I don’t know, but I’m sure that they did have such a category.

Unfortunately, the OED is less helpful on the subject than it might be, as it regards the butcher’s and the dietician’s fat as two aspects of a single meaning, but it gives no example of the dietician’s fat prior to 1860.

For the rest, we must know why Cecil chose to put fat in a distinct list of things “strictly verboten”.