I would like to know the healthiest way to reach a mass of 200 kilograms (440 lbs) without killing myself. I would need to gain 127 kilograms, as I am currently sitting at 73 kilograms at 14% body fat.
First, it should be stated clearly that, for men, body fat of greater than 25% constitutes one formal definition of obesity. Your goal of 35% would not be considered ‘healthy’ by any scientific or medical organisation.
Nevertheless, if we temporarily disregard body fat and consider only lean muscle mass, your goals are still well beyond what evidence tells us is achievable—at least without extreme drug and supplement abuse. A study by Casey Butt, PhD. documented the anthropomorphic measurements, fat, and lean mass of elite ‘natural’ bodybuilders, beginning in the late 1930s, and his findings culminated in a formula that would estimate our absolute (natural) potential for lean muscle gain. And whilst it has been noted that ‘natural’ status of many of his subjects is questionable, it does provide us with some evidentiary foundation for what is practically possible. His formula is as follows:
Whereby H is your height in inches, A is your ankle circumference at the smallest point, W is your wrist circumference at the styloid process, and bf is your body fat percentage.
That research revealed maximum Fat-Free Mass Indices of around 25 kilogram metres (kg.m). For reference, the median (Caucasian) height-adjusted Fat-Free Mass Index (AdjFFMI) of untrained men is 18.9 kg.m, and male college-level athletes have been found to have an average AdjFFMI of 22.8 kg.m, suggesting that those findings are, at least, within the bounds of reason. So if we accept Butt's conclusions and formula, the average man would be limited to approximately 18-23 kilograms (40-50 lbs) of muscle gain after reaching adulthood. The rest would necessarily be fat.
So whilst you certainly could reach your goal mass, since fat is the only component of our bodies for which there is no limit, you could not achieve that goal muscularly or healthily.
I hope that helps.