[johndavi]

The New Yorker had solid overview -- i.e., "how much we know about how little we know" -- of the gut microbiome in 2012: http://www.newyorker.com/magazine/2012/10/22/germs-are-us

The calories-in, calories-out crowd isn't wrong thermodynamically speaking (I am fairly certain!), but an important component of that is how many calories are being taken-up by bacteria and how many are passed through without being utilized. If my gut sucks up 20% more calories from the same food as someone else, I'm going to have a harder time managing my weight than he/she will... even if we eat and 'move' at precisely the same amounts.

[Consultant32452]

While this research is interesting I don't know that it will ultimately be all that valuable to the average person in the real world. For the average person who just wants to lose some weight, we all know that we need to consume fewer calories. And if we still don't lose weight we need to consume fewer calories still. It's not that complicated. The core problem is actually going through with it and sticking to your reduced calorie intake. Getting your gut bacteria algorithm worked out for you isn't going to matter if you're still sneaking in the soda and Snickers as extra calories. I think the only real-world beneficiaries of this research will be people on the far end of the spectrum of health/body hacking like body builders or world class athletes. I suppose also people who are hospitalized for obesity related issues, but those are a small fraction of the population.

[johndavi]

Changes in the gut could be quite profound -- well beyond caloric uptake. It's quite likely that gut bacteria influences mood and other things we commonly attribute solely to the brain. If that's the case who knows the impact gut biome changes could make on desire, "willpower," adherence to a diet, the allure of "soda and Snickers" compared to other foods.

[nommm-nommm]

Gut bacteria effects you in every way possible. Changing your gut bacteria may help you avoid Snickers and soda. Your gut bacteria may be effecting your hunger, motivation, mood, and all sorts of stuff.

See also: Why It Was Easier to Be Skinny in the 1980s A new study finds that people today who eat and exercise the same amount as people 20 years ago are still fatter. http://www.theatlantic.com/health/archive/2015/09/why-it-was...

>They found a very surprising correlation: A given person, in 2006, eating the same amount of calories, taking in the same quantities of macronutrients like protein and fat, and exercising the same amount as a person of the same age did in 1988 would have a BMI that was about 2.3 points higher. In other words, people today are about 10 percent heavier than people were in the 1980s, even if they follow the exact same diet and exercise plans.

Gut bacteria may play a role.