High weight and normal weight individuals have a differential composition of their microbiome. Mechanistic studies have indicated that the microbiota can influence both sides of the energy balance equation; namely, as a factor influencing energy utilization from the diet and as a factor that influences host genes that regulate energy expenditure and storage. Recent studies on overweight adults showed that the ratio of bacteria in the gut co-related with weight loss. Those with higher ratios for particular set of bacteria lost more weight and body fat after 6 months than individuals with a low ratio, despite being on the same diet. It is now clear that weight loss is more depended on what microbes are present in the gut than what food is actually consumed.