Because they did not put sugar in everything. Also, they weren't cooking with vegetable oils.

Without those two it's a bit difficult to get to the point of obesity in a world where you have to walk a lot because cars and elevators don't exist.

But they drank a lot of alcohol ...

Correction: they did put sugar in absolutely everything. Vast quantities of it. Read up on Demerara sometime.

That leaves vegetable oils, and cars. I think it's like 70/30 personally.

Walking everywhere. Mass obesity (there's always been a few obese people among elites everywhere!) is a product of the motorcar.

Also, food unevenly distributed across the day. Any one individual probably wouldn't have a large breakfast and elevenses and a large lunch and afternoon tea and a large dinner, on every single day. Even if you can find examples of each of those separately.

mass obesity is a product of people eating unhealthy. i have access to plenty of luxuries compared to the rest of the world, and even America, yet my BMI is about ~20. individuals are responsible for being fat.

If by individuals you mean the individuals stocking the supermarkets with ultraprocessed foods, maybe.

The timing doesn't work. In the US, obesity didn't start taking off until the 1970s and 1980s, and the motorcar was ubiquitous long before that.

Looking at pictures of Churchill, who was admittedly a bit after the Victorians but seems to have followed a somewhat similar lifestyle, he doesn't exactly strike me as skinny.

I imagine they did have a fair amount of obesity in the older members of the population, although it's also possible that the sportier ones (which I'm guess would have entailed things like polo and horseback riding) would remain fit into old age.