Have you or someone you know ever willingly made a lasting and meaningful lifestyle change? Chances are it was very difficult. Food choices and behaviors are especially hard as they are sometimes cultural and deeply rooted in people's psyche.
Intelligent people have died from diabetes and other obesity related illnesses, not because they couldn't understand calorie math or what carbohydrates are, but because they couldn't or wouldn't change their eating habits in the long term.
If by lifestyle you mean behavioral disorder, It seems to me that the science from the last 10 years is starting to point in the opposite direction. If I may recommend, there is a great presentation by Dr. Robert Lustig called "Fat Chance: Fructose 2.0".
[0]: https://www.youtube.com/watch?v=ceFyF9px20Y
Intelligent people have died from diabetes and other obesity related illnesses, not because they couldn't understand calorie math or what carbohydrates are, but because they couldn't or wouldn't change their eating habits in the long term.