Topic: Research News

Scientists studied what happens to our bodies when we fast for seven days. They found that after three days, many changes occur at a molecular level, affecting brain, metabolism, and immune systems.

Scientists have long known that fasting can help us lose weight and improve our health. But what exactly happens in our bodies during prolonged fasting? A recent study published in Nature Metabolism aimed to answer this question. Researchers from Queen Mary University of London's Precision Healthcare University Research Institute (PHURI) and the Norwegian School of Sports Sciences monitored 12 healthy volunteers as they fasted for seven days on water alone. Blood samples were taken daily before, during, and after fasting. The team used advanced technology to track over 3,000 proteins circulating in the bloodstream, which can provide clues about what's happening across organs and tissues throughout the body.

As expected, the body quickly shifted from burning glucose to burning fat within the first two to three days of fasting. Participants lost an average of 5.7 kilograms (about 12.5 pounds), including both fat and lean tissue. After participants resumed eating for three days, most of the lean tissue loss returned while much of the fat loss remained.

But researchers discovered something more surprising. Large-scale changes in protein activity throughout the body did not begin immediately. Instead, major molecular changes became much more noticeable after around three days without calories. More than one-third of the proteins measured changed significantly during fasting. Some of the strongest shifts involved proteins linked to the extracellular matrix, which helps provide structural support for tissues and organs, including neurons in the brain.

The protein changes were remarkably consistent among volunteers, suggesting that the body may follow a highly coordinated response to prolonged fasting.

Implications

Scientists studied what happens to our bodies when we fast for seven days. They found that after three days, many changes occur at a molecular level, affecting brain, metabolism, and immune systems.