People complain about how easy it is to gain weight. But for scientists, fat accumulation is a complicated process, involving nearly all tissues and organs in the body.

What forms the love handles people want to get rid of so much is technically called fat tissue, which houses millions of fat cells. The fat cells are like balloons, filled with triglycerides, which gradually expand. That means obese people may have "fatter fat cells."

Research has shown that the number of fat cells in both thin and obese people is more or less set during childhood. As a result, an adult has a nearly constant number of fat cells. Changes in the size of fat cells will cause the body weight to rise and fall.

To work out how fat accumulates within the body, the team of Zhao Yue, a researcher from Nanjing University in China, built a high-fat diet model for mice to simulate the state of overeating in humans.

They found that when too much fat flooded into the body, it didn't immediately find its way to the fat tissue, but somewhere else.

"After the mouse eats a high-fat diet, the liver is the first to respond, which accumulated fat earlier than the fat tissue and skeletal muscles," Zhao said.

Scientists have long known that the liver can communicate with other organs from afar, sending out tiny molecules as messengers to regulate distant organs and their functions. But Zhao noticed that one type of molecule, called exosome, only enters the fat cells. That means that there is indeed a communication channel between the liver and fat tissue.

And if you continue to consume a high-fat diet, the information carried by the exosome changes. "After a long time, fat cells can no longer bear the metabolic pressure. The liver changes its order. The number of (fat cells) has reached a peak. Their volume has to become bigger," Zhao explained.

The body's strategy is clear: growing some more fat cells as an emergency measure but then making fat cells fatter in the longer run. However, there's a limit.

After years of binge eating, excess fat will be deposited in the blood vessels, and then the liver, destroying the metabolism.

The fat changes the body shape. But what makes scientists excited is finding the exosomes. The ability of those little messengers to recognize and target fat tissue means new drug options for diseases such as obesity and diabetes could be on the horizon.