Agree that there are a lot of unknowns. Kevin Hall is carrying out some illuminating studies on the issue but, by his own admission, there’s simply not enough funding to do this at pace or scale.

I think we have some experimental evidence to suggest that at least some of the UPF associations are due to texture - those foods that you can basically inhale without chewing seem to drive higher caloric intake. We also have an incredibly strong signal of mass gain from sugar sweetened beverages which are also easy to consume with minimal effort.

I think it’s likely that cultural and economic factors play into this too. Japan has the same proliferation of UPFs, yet does not suffer the same obesity effects as the West does. There are probably a number of things that play into this: Japan has an incredible children’s food education policy, and they presumably have a different culture around food (many western cultures emphasise a “finish your plate or you’re ungrateful” approach).

I also have an intuition that the rise of two income households raising children is a factor in this. It’s a lot to ask of a couple that they both hold down full time jobs while cooking the kind of meals that used to be the domain of a stay-at-home parent.

Really interesting area to think about in terms of research and policies, but as you say we just don’t have strong evidence at the moment.

In the meantime it’s great that GLP-1 agonists are available to reduce the damage done, but it’s a shame we have to resort to such things in the first place.