sat, mono, poly fats-thats it right?
on fitday or nutritiondata, i look up foods, say beef for example. add up sat, mono, and poly fats. it is less than "Total fat"
where'd the rest go?

Some foods contain natural trans fats too.

so would you say the difference is all natural trans fat and nothing else?

Perhaps that total includes the cooking process... Cooking with oils, lards, and butters will increase the fat total.

give us some examples and we'll track help you track down the missing fat.

quick search on beef
http://www.nutritiondata.com/facts/beef-products/7491/2

4.5+6.4+0.6=11.5
Total fat is 14.7

Shenanigans?

interesting... i suspect that there are several stages of analysis, and thus when you're breaking down the fat into subcategories you lose a little bit here and there. i also suspect that no one is putting a lot of money, energy or quality control into these numbers. would be interesting to investigate how this crops up, though your tri-tip example is starker than some others i pulled up for beef.

when in doubt, i would trust the total fat number more than any of the others.

one guess: they are very focused right now on saturated & trans fats, so those are likely to be accurate (unless the numbers are totally missing) and they may be undercounting other subgroups (poly & mono).

another trouble may involve how to count certain fatty acids that are technically saturated but behave in the body more like mono (for example, stearic acid, the primary fatty acid in lard, that is, pig fat).

also, there's a lot of pressure by the meat folks not to reveal how much trans fat appears naturally in animal products, b/c all the evidence against trans fats so far blames only artificially created trans fats, but no one knows for sure & meat/dairy producers don't want to be painted with that same broad brush. but i can't imagine there's that much trans fat in tri-tip to account for your discovered discrepancy.

also, what i'm finding is that the USDA & their counterparts elsewhere are reluctant to "impute" (guess at) missing data, and the quality control in the underlying studies is often atrocious or nonexistent, even for basic & obvious commodities like whole and skim milk.

interesting theory.
it would account for why just about all products seem to have this fat differential, which makes my fat balancing much harder to do.