His point basically is that Sugar is not in any way except for how it contributes to excess caloric intake. The key here is that sugar contains calories and can attribute to hyper-caloric state. But you can also eat lots of sugar and be in a hypo-caloric state. Therefore sugar has nothing to do with it. Total consumption is everything here (and body fat percent).
Have a watch of these videos:
https://www.youtube.com/watch?v=9JrT84PeTgw
It's true that countries where they don't put sugar in everything—or don't use HFCS at all—don't have this problem.
It's also true that between 1950 and 2000 portion sizes went up. For everything. If you travel in France and Italy, known for butter and pasta heavy cooking, respectively, their servings are half the size of the typical American restaurant.
At the same time, if you go from a walking city in the US to a suburb where it's all cars all the time, the visible difference if you just look around at people is jarring. Sure, cities might eat differently, but not that differently.
I'm not anti-car, but in some places the 100% sedentary lifestyle is a big part of the problem.
Sugar is in everything. Snacks, restaurant food, drinks, sauces. It puts the metabolism into a bad state and desensitizes the body to its deleterious effects. Before you know it you're overweight, mentally foggy, and pre-diabetic. Not a good place to start working out or going for outdoor activities.
People exercise and walk more when they have energy to do so. Sugar saps that away.
Look at people in other "confined" spaces: submarines, ships, the space station. These people are not overweight for lack of walking.
It's diet.
America is pumped full of sugar.
edit to respond to comments (since I'm flagged / rate limited) :
Someone with a healthy body and mind won't "sit on their ass 23 hours a day". They won't consume too many calories, either.
Sugar pushes the body into more lethargy and higher sugar consumption.