Bigwideland:
Here is a thought, when people get to 800 they generally maxout what is possible. But could genetic engineering give people the ability to avoid the health limitations and wake 1500 to 2000 lbs people possible. What do you think?
To put it bluntly, no. No matter how good your genes are, your body is not meant to weigh past a certain point. While that limit varies from person to person, at some point, your body will disintegrate from the sheer amount of mass.
If you somehow manage to avoid things like clogged arteries, diabetes, and the like, you cannot overcome your structural integrity limits. Even if you spend the rest of your days in bed, your heart and lungs will struggle to move enough oxygen and blood throughout your body.
You cannot genetically engineer a circulatory system that works better at larger sizes because it will not work at smaller sizes. After all, you aren't automatically 1,500 - 2,000 lbs. And you cannot correct this when you get bigger because the surgery would kill you.
With that said, genetic engineering could make you more resistant to morbid obesity comorbidities and lower weights. It could also facilitate a more comfortable weight gain overall.