You don't usually see many obese people in Oslo these days either. There's certainly a higher average weight now than in these photos, but US-style excessive obesity is rare in Norway.

Edit: As of 2019, apparently 3 % of Norwegians are obese (BMI >= 35), while a whooping 30 % are bulky or somewhat fat with a BMI of 27-35. Obviously with the shortcomings inherent in BMI, e.g. not accounting for low fat percentage etc. Too bad the data don't go any higher, it would be interesting to see how many are excessively obese, i.e. BMI of, say, 150 or more.

https://www.ssb.no/statbank/table/06181/tableViewLayout1/

He just didn't photograph them. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2317764

Or maybe the photographer simply didn't take pictures of obese people, for whatever reason.

Good observation