This is false.

Food deserts and lack of financial/nutritional education are a major cause of obesity. Many Americans don't have quick access to grocery stores and can only purchase fast food / junk food. They literally don't have time or the ability to change what they eat. Some Americans have grocery stores but literally do not know that healthy food CAN be cheaper. They see Whole Foods and rich people eating healthy and intuitively it makes sense that it seems more expensive. These are problems outside of individuals that exist on a national and global scale.

> Distance to store and prices were positively associated with obesity (p<0.05). When distance to store and food prices were jointly modeled, only prices remained significant (p<0.01), with higher prices predicting a lower likelihood of obesity. Although low- and high-price stores did not differ in availability, they significantly differed in their display and marketing of junk foods relative to healthy foods.

https://www.sciencedirect.com/science/article/pii/S074937971...

Is it addiction? Is it some biological process (the body wanting to retain its new equilibrium)? Is it the fact that my taste buds tend to prefer the flavors of unhealthy food a majority of the time?

Clearly the problem is bigger than obese people being aware of their obesity and trying (and failing) to change it. There are other forces at play, and I think, difficult ones to overcome.

Separately, why not still try to innovate or do something to reduce the burden obesity places on the healthcare system (regardless of how you feel about the individuals)?

On the contrary, obesity likely exists because evolution optimized for the ability to survive long famines, which isn't a big problem in most developed nations nowadays.