High levels of sugar consumption appear to promote obesity and change gut microbe flora.
Weight control and obesity are huge problems in the united states and they are growing as fast as the average waistline. Obesity is the single largest growing health issue in the United States. We all know that increased caloric consumption is tied to obesity but there are arguments whether certain foods may contribute more than others. No matter whether certain caloric sources can cause obesity more than others, it is clear that the consumption of diets rich in energy in excess results in weight gain.
The good news is that new research has sought to look at high sugar and high-fat meals as a means to cause obesity  . Notably, the research looked at where obesity and weight gain might be tied to the popular dietary approach for weight loss by reducing fat intake. This study also looked at sugar intake. The study was completed on rats but should have a similar response in humans.
In the study, rats were fed one of three diets: a high-fat/high-sugar diet, a low-fat/high-sugar diet, or a low-fat/low-sugar diet. The intervention was implemented for 4-weeks, and researchers monitored body weight, caloric intake, and body composition daily. Both high-fat, high-sugar diet and low-fat, high-sugar diet-fed rats displayed significant increases in body weight and body fat during the experiment when compared to the third group. The study also found that this intake changed the gut microbes and might indicate a potential cause or effect.
The bottom line: The studies indicate that high-sugar diets, irrespective of fat intake, and tied to significant weight gain in rats. We would expect similar results in humans, and prior research has found near-identical results. The dysbiosis of gut microbes increases gut inflammation and appears to alter vagal gut-brain communication. Both changes are associated with an increase in body fat accumulation. More research is needed, and human studies are warranted.