What happens when you suddenly stop exercising?

Just two weeks of inactivity is all it takes to reduce muscle mass and produce metabolic changes that could lead to an increased risk of developing chronic diseases, obesity experts warn. 

In a study of young, healthy adults with a mean BMI of 25, UK researchers have found that switching from moderate-to-vigorous activity to near-sedentary behaviour for just 14 days raises the risk of type 2 diabetes, heart disease and even premature death.

Following the period of inactivity, significant changes in body composition were observed, including increases in total body fat, particularly around the abdomen.

Cardiorespiratory fitness levels declined sharply during this short time frame, and participants were unable to run for as long or at the same intensity as they previously could.

A substantial loss in skeletal muscle mass was also noted, with a reduction in both total (whole body) lean mass (average loss 0.36kg) and leg lean mass (average loss 0.21kg). 

Mitochondrial function also declined, but this was not statistically significant.

Such changes can lead to chronic metabolic disease and premature mortality, notes lead researcher Dr Dan Cuthbertson of the University of Liverpool in the UK.

“The results emphasise the importance of remaining physically active and highlight the dangerous consequences of continuous sedentary behaviour.”