Comment Calories in/Calories out is not science (Score 2, Insightful) 909
Science would be to actually test how well diets and/or exercise work on a group of people. And over and over for decades such studies have shown that the weight lost is very small, and what weight is lost isn't maintained. That goes for studies of animals too. That's science. And it is true that most clinicians ignore that science and give advice based on a hypothesis that has been for the most part falsified by in vivo studies.
The reason the hypothesis fails is because the system that's been blackboxed regulates fat homeostatically. Just like hydration, carbon dioxide levels, and temperature are regulated - fat mass is also regulated - largely through hypothalamic monitoring of circulating leptin and insulin levels.
What most people don't understand - because they don't plug numbers into the equation - is how closely the body has to maintain the energy balance. A 1 or 2% overage or underage will rapidly lead to massive obesity or death by starvation. So there's a very powerful and very finely tuned system that controls how much we eat and how much we expend by monitoring our fat mass. This is true of the very fat and the very thin. It makes sense when you think about it, but most people don't.
So the body aggressively tries to maintain homeostasis - that is keep fat mass within a given range - by adjusting appetite, metabolism, the relative deposition and breakdown of lean mass and fat mass, and the various forms of physical activity. You have some conscious control over some of these factors, but when you start falling outside the comfortable range - whether or not you are still "fat" - you are fighting homeostatic controls that are very hard to keep at bay long term.
(Generally people who are well below their comfortable range feel extremely hungry, tired and slothful, cold, depressed, etc. And most of all they become obsessive about food. As you can see these are all the body's ways of trying to encourage a positive energy balance. And it's no way to live.)
This kind of mechanims is why it would be very difficult to maintain dehydration indefinitely without drinking. And this is also why it's easy to hold your breath for 10 seconds, but not 3 minutes.
Most fat people - like most thin people - are staying within their range - and most who aren't trying to lose weight and thereby weight cycling maintain remarkably stable weights - just higher weights than we would like.
The real long-term solution to obesity will probably come from finding ways to manipulate the set point so that individuals with dangerously high weights don't have to live their entires lives battling (for the most part futilely) powerful internal regulatory controls just to maintain a weight loss. It is possible that the set point can also be prevented from going too high - but that too is just a hypothesis at this point, and how that can be accomplished isn't clear.
But that understanding among obesity researchers is why most of the focus on obesity is now on prevention in children. And why the research is targeting earlier and earlier ages - including the prenatal environment. I'm not entirely sure that that's a clear-headed strategy because as of yet there have been no interventions shown to be successful at preventing obesity in children either. But there is less evidence than in adults that the project is futile.
