Why is there an obesity epidemic?

Why is 2/3 of the US overweight and 1/3 obese?


I have read too many quack “Garry Taubes” inspired ideas of carbohydrates etc., on MFP. But all these ideas are selectively using data and do not follow basic scientific principles, like calorie in and calorie out. Note if you reject basic science or evolution, think that there is a government/industry conspiracy making us fat and sick, please stop reading and go to your favorite quack blog. I don’t want to argue about basic scientific facts.





But the question is there, why is there the worldwide universal increase in obesity?


The most common hypothesis I have seen is the thrifty gene idea. We humans over consume food to be ready for lean periods. Or in other words evolution will favor humans that have genes that allow us to more efficiently use energy. Thus the obesity increase is because we just have too much food available and the lean times never arrive. And our food industry is very good at providing us with so much tempting, cheap, readily available food that we just can’t help ourselves. If this is true, well then we are pretty much stuck with the obesity epidemic, unless we regulate the food industry to make the food less tempting/available/cheap so that we lower energy intake.


Alternatively, what about antibiotics? Antibiotic use started in the 1950 and now are widely used by humans and also, even more, in the animal food industry. Antibiotics are a major food supplement, because antibiotics lead to higher animal weight gain, i.e. animals gain more weight per unit food intake. Or in other words, animals get fatter on the same amount of food. This is likely caused by evolutionary microbial community population changes. I can see that within a normal gut microbial population, evolution will favor those microbes that use energy/nutrients most efficient, which may lead to lower energy available for the host. Whereas antibiotic use will select for antibiotic resistance and not energy efficiency. Thus, an antibiotic influenced microbial gut fauna will be less efficient in using energy, leaving more for the host, allowing the host to absorb more energy from the food that it eats.

Of cause this also works the other way around, to increase weight gain, add an antibiotic to your diet (http://www.nytimes.com/2013/01/31/health/antibiotics-can-save-lives-of-severely-malnourished-children-studies-find.html?_r=0 )


Thus getting fat is, not just, the result of calories in, calories out. We need to consider the difference between the calories that we eat, the calories that we actually absorb and that we use, something that MFP can’t track. And our gut microbes are the key factor in this. And there are a lot of recent articles showing all kinds of correlations between the gut microbial fauna and obesity, diabetes, etc.

Let’s call this the antibiotic microbial selection - induced obesity hypothesis. (And of course there are very few original ideas anymore these days, there are articles arguing the same as I do here, see for instance (http://www.infektologia.hu/upload/infektologia/document/antib_growth.pdf)


So, if this is true, well than the use of all those antibiotics in the animal food industry is plain stupid, but just because of potentially creating antibiotic resistance in diseases (http://www.nytimes.com/2012/09/04/health/use-of-antibiotics-in-animals-raised-for-food-defies-scrutiny.html?pagewanted=all ), but also because antibiotic driven evolutionary microbial genetic changes may be driving the obesity epidemic.

Thus, if this is true, eliminating antibiotics as an animal food supplement has to be done, and all of us should limit antibiotic use as much as we can, especially in children.


Anything I am missing here?


And what other hypotheses explaining the obesity increase are out there?