Talk about good timing, I've started reading The End of Food and the first part of this article ties in nicely with that.

And yet, scientists still could not explain the mystery of antibiotics and weight gain.

I believe this is caused by antibiotics killing off bacteria in the digestive system, and they actually bring that up later in the article. Somebody with a bio background would have a greater understanding of how that works than I do. Having an "anti-antibiotic" though, isn't that just a probiotic? The development of which is very interesting, having control over a microbiome like that would be a great health development, I would hazard to guess.

In 1955, a crowd gathered in a hotel ballroom to watch as feed salesmen climbed onto a scale; the men were competing to see who could gain the most weight in four months, in imitation of the cattle and hogs that ate their antibiotic-laced food. Pfizer sponsored the competition.

Nowadays we do that in a single ten-minute long competition in which a group of people see who can eat the most hot dogs. Good to see that not much as changed.