Toxic substances leaking out from the gut can interfere with the functioning of fat cells and drive obesity, according to a recent study by a team of international researchers. The results could inform how we treat excessive and dangerous weight gain in the future.

The substances, called endotoxins, are fragments of bacteria in our guts. While they're a normal part of the digestive tract's ecosystem, the microbial debris can cause significant damage to the body should they find their way into the bloodstream.

Here, the researchers wanted to look specifically at the impact of endotoxins on fat cells (adipocytes) in people. They discovered that key processes that usually help control the buildup of fat are affected by the material.

"Gut microbe fragments that enter the bloodstream reduce normal fat cell function and their metabolic activity, which is exacerbated with weight gain, contributing to increased diabetes risk," says molecular biologist Mark Christian from Nottingham Trent University in the UK.

"It appears that as we gain weight, our fat stores are less able to limit the damage that gut microbe fragments may cause to fat cells."

The study involved 156 participants, 63 of whom were classed as obese, and 26 of whom had undergone bariatric surgery for obesity – a procedure where the size of the stomach is reduced to limit food intake.

Samples from these participants were processed in the lab as the team looked at two different types of fat cell, described as white and brown.

White fat cells, which make up most of our fat storage tissues, stores lipids in larger volumes. Brown fat cells take stores of fat and break them down using their numerous mitochondria, such as when the body is cold and needs warmth. Under the right conditions, the body can convert the lipid-storing white fat cells that behave like lipid-burning brown fat cells.

The analysis showed that endotoxins reduced the body's ability to turn white fat cells into brown-like fat cells and reduce the amount of stored fat.

This browning process is crucial in maintaining a healthy weight, and if scientists can figure out more about how it works and how to control it, then it opens up more potential treatments and therapies for obesity.

"Endotoxin from the gut reduces fat cell metabolic activity and its ability to become brown-like fat cells that can be useful to help lose weight," says Christian.

We know that the guts of obese people are less resilient than normal, so endotoxins have more of a chance to escape. What this study also shows is that those leaking substances are then making it even harder for fat cells to function normally.

The study authors also point out that bariatric surgery reduces the levels of endotoxins in the blood, which adds to its value as a weight control method. It should mean that fat cells are more able to function normally.

All kinds of factors play into how our weight is controlled on a biological level, and now there's another significant one to consider. With obesity and its associated health problems becoming more of a problem worldwide, we need all the insight we can get.

"Our study highlights the importance of the gut and fat as critical interlinked organs that influence our metabolic health," says Christian.

"As such, this work suggests the need to limit endotoxin-induced fat cell damage is even more important when you have excess weight, as the endotoxin contributes to reduce healthy cellular metabolism."

The research has been published in BMC Medicine.