After 6 days of inactivity, people develop the first symptoms of type 2 diabetes

The initial signs of insulin resistance (the reason why people develop diabetes) can be observed after just 6 days of complete bed rest. This is revealed in research conducted by a team of Movement Scientists from the Vrije Universiteit Amsterdam (VU Amsterdam), led by Moritz Eggelbusch and Rob Wüst in collaboration with the Manchester Metropolitan University, ESA, and NASA. The results have been published in Cell Reports Medicine.

"Understanding the impact of physical inactivity on human physiology is crucial, not only for astronauts to maintain their health and fitness in space but also for the well-being of people on Earth", says Eggelbusch.

Eat less, move more
Physical inactivity or the lack of muscle use contributes significantly to metabolic diseases. The negative consequences of physical inactivity also occur during hospital visits, where 6 days of bed rest is typical for patients undergoing major surgery. "Our findings strongly suggest that we should make an effort to prevent excessive nutrient storage in the muscles and its metabolic consequences, either through physical activity and/or reduced nutrient intake," says Eggelbusch.

Muscle damage
The findings may lead to a new approach to alleviate harmful changes in muscles during physical inactivity. The research also showed that the accumulation of unhealthy fats coincided with a deterioration of muscles and metabolism after two months of bed rest. However, it was notable that further accumulation of this type of fat between 6 and 55 days of bed rest did not worsen insulin sensitivity. This contradicts the conventional understanding of the development of type 2 diabetes.

"This sheds new light on the development of insulin resistance, indicating that it is a positive adaptation of the body to minimize further harmful effects of glucose and fat accumulation in muscle tissue. For muscles, it is beneficial to be insensitive to sugar because it can prevent further accumulation and damage in the muscles", according to Wüst.

Gravity as a preventive measure
The impact on the body of prolonged bed rest is similar to what astronauts experience in space. At the German Aerospace Center in Cologne, the group, in collaboration with the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), studied 24 healthy participants who underwent 60 days of strict bed rest. All experiments, meals, and leisure activities took place lying down. Participants were restricted in their movements, reducing the strain on muscles.

"The beds were inclined at an angle of 6 degrees, with the head lower than the feet to simulate the displacement of body fluids that astronauts experience in a microgravity environment. For the first time, the potential of artificial gravity was investigated (centrifugation at about 1G at the level of the navel) as a preventive measure against the adverse effects of weightlessness on the human body", says Wüst.