Obesity is interesting because I regard it as a partially-solved problem. For example, dinitrophenol would solve much of it: it makes mitochondria less efficient and so effectively increases metabolism, but at the cost of emitting waste heat - which is potentially fatal and got it banned despite its apparent effectiveness. It could still be safely used; it's 2013 so electronic thermometers are a dime a dozen. Take patients to a fat camp, dress them in clothes with thermometers constantly recording and now doses can be adjusted based on detailed data and the thermometers can warn the patient to jump into conveniently located ice baths. Voila. And I'm not clear on how dangerous it really is when not made illegally and used recklessly by young kids; Wikipedia cites a 1934 paper as estimating that there were ~100k users of DNP before it was banned, and those authors remark, after discussing the grand total of 4 deaths up to that point due to the drug's use under medical supervision, that

When one considers that some one hundred thousand patients have been treated with this exceedingly potent therapeutic agent, it is a matter of some gratification to know that fatalities have not been more numerous. It might be added in this connection that fatalities from the fever of dinitrophenol can be largely prevented, in animals at least, by chilling the skin with ice packs and by giving oxygen inhalations.17

It would seem that like the War on Drugs in general, the attempt to reduce the harm from DNP has resulted in far more harm than was ever the case before.