What Happens to Your Body After Fasting for 7 Days?

While Intermittent Fasting has long been a concept adopted by fitness aficionados, the idea of fasting itself spans civilizations such as the ancient Greeks, Romans, and Egyptians. In addition to theories around detoxing and boosting the immune system, some people undertake extended fasts in the hopes of harnessing potential metabolic effects such as improving insulin sensitivity and better cell health. But what happens when an individual abstains from food for 7 whole days? A new study has the answers.

The Effects of Fasting for 7 Days

The study, published in Nature Metabolism, hoped to understand the positive and negative effects of a seven-day fast, in order to determine its suitability as a therapeutic intervention. Twelve volunteers who were in good health consumed just water for 7 days. As expected, one of the initial reactions to the fasting was for the body to switch energy sources, from glucose to body fat. Within three days, the participants lost an average of 12 pounds (5.7 kilograms) in body mass.  But perhaps more surprising was rate at which the mass returned following the fast. While a resumption of eating for three days returned the lean body mass, the body fat stayed off.

In addition to the findings relating to body mass, the scientists also found that specific proteins were restructured during the fast, such as those proteins that support the structure of brain neurons. While more work needs to be done to understand the consequences of these protein changes, and ideal fasting durations, the researchers also uncovered beneficial reactions that could aid in the treatment of rheumatoid arthritis and heart disease. “Our results advance our understanding of prolonged fasting in humans beyond a merely energy-centric adaptions towards a systemic response that can inform targeted therapeutic modulation,” reads the report.

Still, the study was also keen to point out that there are adverse effects associated with fasting that also need further understanding. Prolonged fasting is not something that one should attempt at home without proper medical advice and supervision, since it can cause electrolyte imbalances and negative consequences due to nutrient deficiencies. Always consult a health care provider before undertaking any type of fast.