What has the phlogiston theory to do with the belief that the only cause of becoming overweight is eating too many calories and taking too little exercise? - Well both theories are out of date.
In the 18th century the phlogiston theory of explaining combustion and breathing held sway until the 1780s when Lavoisier discovered oxygen and explained its role in burning and rusting, etc. The calories in/calories out theory for excess weight presently held by most of the orthodox medical world is an oversimplistic explanation for the excess weight. Essentially it says that overweight people eat too many calories and take too little exercise, ie they are greedy and lazy. The glaring omission is the fact that a great deal of excess weight has nothing to do with calories at all! - That is because it is water - and there are no calories in water!
Professor Sir Richard Doll wrote in a personal letter to me in August 2001, "I was interested to hear about your experience of being overweight and losing so much weight when you reduced the amount of salt in your food. That a high salt diet combined with certain drugs (of which steroids are an example) will lead to water retention is - or ought to be - well known and, of course, the contrary follows that reducing the salt will lead to the loss of water."
There are so many prescription drugs and classes of prescription drugs, and doctors are constantly being exhorted to prescribe more and more drugs, especially antidepressants, many of which cause water retention and its attendant health problems, notably stroke, high blood pressure and heart conditions, that I would contend that the ever-increasing numbers of prescription drugs being taken must certainly be the cause of a high proportion of obese people being overweight. An additional danger is that so many prescribed drugs are addictive, especially painkillers. So I hope that the theory that the only cause of becoming overweight is eating too many calories and taking too little exercise will soon, like the phlogiston theory of combustion, be consigned to the dustbin of history, and people can be saved from all the ill-health that so many prescribed drugs cause.