>The world didn't suddenly decide to get less active all of a sudden
In many ways, yes it did. There is a shocking decline in active calories in every developed country, and it has been exported to the developing world as well. People are astonishingly lazy, on the average.
Like, Christ, it's so bad that the recommendation to take a brief, slow walk after meals is revolutionary now. Because the average person just waddles to their chair and then "digests". It is astonishing how lazy the average person is in many countries.
>It has to be really high. We are talking about hours to burn up that bowl of frosted flakes.
I love that you declare that I'll be "in for a surprise", as if you're educating me. Hilarious stuff.
In any case, really high is...a bit of an exaggeration. I cycled 30km this morning, at the crack of dawn. A fairly casual, 20km/h or so ride down to the lake and back. That's an estimated 900 calories, or about three bowls of frosted flakes with milk. And the fun thing is that I didn't even eat this morning and did it purely on glucose reserves. This wasn't some athletic thing and was very much a casual "catch the end of summer" thing. Actual athletes absolutely destroy those numbers. People engaged in basic recreational sports destroy those numbers.
And that bike ride is something people would do just getting to and from places in the not to distant past. Where people were constantly moving and doing. Now most of the readers of this comment will have done nothing today beyond moving from seat to seat in various transporters and digestion chambers.
We've all been around someone who is spectacularly lazy who'll tell you about their "metabolism", and who'll jealously jeer when a peer eats without concern and somehow stays healthy. In the vast majority of cases, the latter person is active in their life, and the former person is one of those seat-to-seat people. Being active impacts every facet of your life, and endless choices throughout the day, and it yields an enormous impact on your health.
edit: meant to address the fructose. The fructose converted to glucose does so slowly enough that there is a marginal impact on blood sugar. And the average person consumes multiples more glucose than fructose. Should people consume less fructose (ergo sugar, even if the current admin is trying to healthwash sucrose)? Absolutely. But glucose and simple carbs are the biggest vehicle towards blood sugar and overwhelming glucose reserves.