Is your gut bacteria to blame for your excess fat? Likely it is. We've known since the 1950s that giving livestock low doses of antibiotics fattens them up fast. The younger the animals are, the stronger the effect. A boom for the livestock industry! Then, in December 2013, with concerns over superbugs and antibiotic resistance, the FDA discouraged the use of antibiotics for the sole purpose of increasing the animal's weight. (This restriction is to be phased in over the next three years. Livestock, however, can still be given antibiotics for prevention and treatment of disease.)
It would be ignorant of us to think that giving humans antibiotics wouldn't also impact our weight. Dr. Martin Blaser MD, the director of NYU's Human Microbiome Program and a former chairmen at its medical school, has postulated that the widespread treatment of young children with antibiotics has caused changes in our gut bacteria (called microbiota) and this may be contributing to the rapid increase in childhood obesity.
While obesity has increased three-fold over the past 15 years, more disconcerting is that the higher the body mass index (BMI) range, the more magnified the increase. Since 1989, obese individuals with with a BMI of greater than 30 have doubled, the number of individuals with a BMI of greater than 40 has increased five-fold and the number of those with a BMI greater than 50 has increased ten-fold. Clearly, something more is at play than that just gluttony, slothfulness and processed foods.
Research now suggests that our microbiota can make us fat or skinny. Obese people have a different gut microbial composition than lean people. They have a higher ratio of Firmicutes to Bacteroidetes. One study even found that individuals who had undergone gastric bypass surgery have very different microbe composition from obese people. Firmicutes and Bacteroidetes are bacterial groups not strains. As yet we don't know exactly which strains do what, but we know what happens when the ratio of these to groups increase: more fat!
Researchers now suspect there are a few ways these obesogenic bacteria fatten you up: