i'm not an expert in this field, but during my personal ketogenic diet research, i came across many elite but amateur endurance athletes blogging about their switch from carb-adapted to fat-adapted performance.
to a layman like me, it would seem that professionals wouldn't be publicizing the fact that they have switched to fat-fueled endurance training because it would be a massive competitive advantage.
the research in this area of biology is extremely cutting edge with new information being published monthly, and i can only imagine well-funded professional athletes are simply training/eating and performing at a level far and away beyond the typical enthusiast or fitness athlete. not only that - they can sustain a specialized, ketogenic diet required to actually achieve such a state.
Except it's a disadvantage, not an advantage. All kinds of diets have been tried in the name of performance and the results are pretty clear. The typical world class runner's diets in the top performing country (Kenya) has 76.5 percent of daily calories consumed as carbohydrates. This group of runners has absolutely demolished lower carbohydrate consuming western runners. Marathoners from other top-performing countries (Ethiopia and Japan) have similarly been scrutinized with similar results.
the proper experiment would be to take half of the kenyan runners and fat-adapt them, and compare their performance to the other kenyans, as well as their previous selves.
has that study been done?
You're not going to find a "proper" experiment, but many, many athletes experiment with their diets, and ketogenic diets are pretty well explored ground. Athletes and coaches alike gravitate towards what yields results. Running is an extremely competitive sport with few barriers to entry and the claim of such a low-hanging "massive competitive advantage" is an extraordinary one that requires extraordinary evidence to be taken seriously.
As for the obesity argument, I think there are two things to consider here: 1. sweet foods are calorie dense. Hence, it's easy to consume too many calories until you feel full. 2. they also have a high reward factor, so it's likely that you would keep eating even after you're full - there's always room for dessert!
Though, these problems not limited to sugar/hfcs. Fructose-free sweeteners suffer from them as well.
Carbohydrates shouldn't be unobtainable or something just for the rich, but a bag of gummi bears should no longer be 2 ten thousandths of a cent per calorie.
http://www.wolframalpha.com/input/?i=%2412.25+divided+%285+p...
I would hate for ignorance to turn the essential sugar fuel I need to ride 100 miles on my bike (no, it turns out, you don't want to do that on fat metabolism alone!) into some unobtainable luxury.