SamanthaM

So basically the reason why you gain weight is because you eat too much. However it it theorized that the efficiency of how your body stores fat is based on the microbial ecology in your gut. We greatly benefit off of the 100 trillion microorganisms that reside in our gut, because they perform maintenance in our bodies that we would not be able to do without.
The differences in gut microbial ecology between humans may be an important factor effecting energy homeostasis. Those who are more susceptible to obesity may have more of an efficient gut microbial community promoting the extraction and the storage of energy from any given diet compared to the communities in lean individuals.
In order to study this theory further, mice with a mutation of the letpin gene allowing the mice to be tested susceptible to obesity and observe them compared to their lean mice siblings. Through this experiment, 3 soon to be mothers of the offspring, of the genetically altered litters were used to produce different litters. The offspring of this mating wave were observed and data was collected.
As a result the “obese”liter consumes 4% more than the lean siblings resulting in significantly greater body weights, as well as epidiymal fat-pad weights. Long story shirt the development of obesity in mice affects the relative abundance of the major gut bacterial content derived from the mother.
On the other hand, regardless of family membership, the cecal microbiota of obese mice had a statistically 50% reduction in Bacterioidetes and a significantly greater proportion of Firmicutes. The observation of 2 different mice (obese traits vs. lean traits) with the same body mass, however the “obese” mice had a significan’ty greater ratio of epididumal fat-pad mass to total body mass.
So even though you can blame your weight gain on your caloric intake, you can also take into consideration how well your gut is doing it’s job. You can thank your mom for that.

http://www.pnas.org/content/102/31/11070.full