Studies were performed on the microbiome. They took identical human twins who have exactly the same genetics. One was normal weight, the other was overweight. They took the microbiome from the twins and implanted it into mice. The mice implanted with the overweight twin’s microbiome ended up gaining weight. The mouse that was implanted with the normal twins microbiome stayed at the same weight. Even though they were feeding them the same amount of food. Then they wiped out the mice microbiome with antibiotics, and they switched it. The overweight mouse started losing weight and the regular weight mouse started gaining weight. The type of microbiome you have changes how your body responds to the food you eat.
The composition of the microbiome is really critical when it comes to obesity. Composition is driven by dysbiosis. Dysbiosis is a microbial imbalance. Most commonly in the gastrointestinal tract. It can be caused by antibiotic use, alcohol abuse, mold exposure or diet. It can lead to inflammatory bowel disease, colitis, autoimmune disease, chronic fatigue, obesity and cancer. The imbalance alters intestinal permeability.
An increase in firmicutes and a decrease in Bacteroides ratio changes metabolism. A fast food and processed food diet high in protein, sugar and fat causes an increase in firmicutes. Obese people often have an increase in firmicutes.