Presumably it's difficult to figure out individual grocery spending, so they measured the household level spending.

So when one (or more) people in a household begins taking the drug, the household spending goes down by that much.

How can they measure individual grocery spending habits? People buy groceries for their whole household.

If the dataset includes household size you could limit the analysis to that subset. Alternatively you could focus on households with lower average basket sizes and hypothesise that those households have fewer adults. Obviously those measure aren't going to be anywhere near perfect but might be informative.

Tracking household size as part of the study.

See my parallel comment... are they reporting 1/4 of a household eats 25% individually (for a 5% reduction across a family of 4). Or, does one person eating 5% less cause the other 3 to also eat 5%... if it's the latter, this potentially has health impacts across people who aren't taking the drug.

> Or, any one person in the household causes a 5% reduction for the group?

I'd go for this one. Which means the one person reduces their food intake by at least double the 5%.

Or possibly the other people in the household see them eating less and follow their example...

Yeah, that's probably correct - it just feels like a really odd way to present the data.

What I'd like to know is your last bit - is one quarter of a household eating 25% less on their own, or does "mom" on Ozempic cause "dad and 2 kids" to eat 5% less individually? The former isn't nearly as interesting to me as the latter...

You ever shop hungry? You buy way more, and often not the stuff you should be buying.

If the primary shopper in the household is on GLP-1, I would expect the household expenditures to drop.