> I wonder why it caused so much negative reaction? On the surface it shouldn't matter much, since it does not appear to harm ones who found a way to maintain healthy body without drugs. Yet it reliably causes a quite noticable number of folks to be quite aggressive towards either people using these drugs or companies making these.
It's a combination of people thinking it violates the 'no free lunch' axiom of the universe and also deriving significant personal status and satisfaction from exerting discipline in eating and exercising religiously.
The 'no free lunch' axiom is a curious thing and seems derivative of western Puritanism and similar philosophies. It violates many people's intuitions that very good things might be obtained with relative ease, and also devalues said things. Some of these are the same people who cannot comprehend (or even accept) a post-singularity world without work. The peculiar morality that produces that belief overlaps rather substantially with the one that rejects the possibility of an easy solution to the problem of obesity.
Further, some of these people have the (perhaps unconscious) belief that they are morally superior to others who are less dedicated to health and fitness, and in particular to the obese.
If obesity can be resolved so fluidly and categorically, then at least two painful things happen for them: (1) their excessive effort towards weight control seems foolish and inefficient (i.e. devalued, as noted above) and (2) they lose a great deal of personal status. The latter is a consequence of the reasonably established notion that a significant proportion of many peoples' happiness is contingent on their relative frames of reference (i.e. not their position in an absolute sense). Again, this is often unconscious. These are not "bad" people, but rather merely victims of human instinct.