A new study shines new light on gut bacteria, fiber, and obesity.
Obesity is linked with metabolic syndrome, a cluster of conditions that include hypertension, high blood sugar, excess body fat around the waist, and abnormal triglyceride or cholesterollevels.
As obesity rates continue to soar, understanding how these conditions work together and what can be done to prevent them is more pressing than ever.
Metabolic syndrome is now considered to be a chronic inflammatory disease, involving altered relationships between gut bacteria and the gut.
Western society has experienced a huge shift in eating habits in recent decades; there is now a much greater emphasis on processed foods, which, notably, lack fiber. This has had an impact on gut bacteria and, according to some, could help explain the increased prevalence of metabolic syndrome.
A diet lacking fiber alters the composition of gut bacteria, lowering numbers overall and changing the ratios of species. Also, low-fiber diets increase bacteria’s ability to encroach upon the gut’s epithelial cells; this provokes an inflammatory response.
Reduced fiber, altered gut
A paper, published recently in the journal Cell Host and Microbe, explores the relationship between obesity, gut bacteria, inflammation, and fiber intake in new detail.
Earlier studies have shown that supplements of a fermentable fiber — inulin — reduce fat buildupand the symptoms of metabolic syndrome. However, consuming enough inulin comes with negative consequences, such as flatulence and bloating. For this reason, understanding exactly how fiber imparts its health benefits is important. Once the mechanism is described, it might be possible to find more efficient, less windy ways to achieve the same goal.
A team of scientists — led by Dr. Andrew Gewirtz, professor at the Institute for Biomedical Sciences at Georgia State — recently set out to develop a clearer picture.
Earlier studies have concluded that short-chain fatty acids (SCFAs) may play a role in reducing inflammation and improving metabolism; this is thought to be mediated by the activation of free fatty acid receptor GPR43. Dr. Gerwirtz and his team wanted to test this theory.
Fiber’s role in the gut and beyond
To answer these questions, the researchers fed mice with one of two diets, both of which were high in fat and known to induce obesity in rodents:
- Low fiber content (5 percent cellulose as a source of fiber)
- High fiber (either inulin or insoluble cellulose)
As expected, after a 4-week period, the mice fed the diet enriched with inulin showed reduced obesity and a reduction in the size of fat cells; the inulin-fed mice also had lower cholesterol and lower incidence of abnormal blood sugar levels (dysglycemia).
