major co-incidence today as my PBS station was putting on it's fundraiser series of every diet plan guy in the world. So much fluff to info, but one person was arguing this same viewpoint (gut biota and tendency to be obese) and showed a startling pair of maps - one with the level of antibiotic prescription and the other with the level of obesity. Startling overlap. Google "antibiotic obesity map"
Theory being that the use of antibiotics disturbs the balance or microbes and set more of the population up for obesity.
Since the idea is that different bacteria feed on different foods this comes back to skipping refined cards and sugars and eating more vegetables - basically the same kind of prescription they all end up with - and trying to skew the population faster with probiotics.
On thing I do now is that every thin person out there is not a paragon of good eating and exercise and not every fat person is a pig with their head in the trough. I was never a skinny person but got progressively more massive with age until one doctor finally thought to test my thyroid which was pretty much crapped out. On the synthetic stuff now and slowly morphing back to - well, something thinner.