Just two weeks of inactivity in healthy young people can reduce muscle mass and lead to an increased risk of developing type-2 diabetes and heart disease, according to research at the University of Liverpool (but see our analysis below).
The research provoked headlines that might have unsettled holidaymakers. ‘Two-week holiday could be the death of you,’ said the Telegraph. The Sun, slightly more soberly, merely suggested that it ‘increases the risk of an early death’.
The study, which was presented at the European Congress on Obesity in Portugal, included 28 healthy, physically active volunteers with an average age of 25.
The subjects underwent comprehensive health checks which measured fat and muscle mass, mitochondrial function (which regulates metabolic activity) and general physical fitness. They wore armbands to measure their physical activity.
Over two weeks the volunteers reduced their physical activity by more than 80 per cent (from 10,000 to 1,500 steps a day). The time they spent sedentary increased by an average of 129 minutes a day.
After this two-week period the researchers observes ‘significant’ changes in body composition, including an increase in total body fat and loss of skeletal muscle mass (an average loss of 0.36kg). They noticed that the body fat accumulated centrally, which increases the risk of developing chronic illnesses.
The subjects were no longer able to run the same distances or exercise at the same level of intensity as they could before. Their mitochondrial function also declined, but not in a statistically significant way.
Dan Cuthbertson, the study’s lead author, said: ‘In a group of physically active, healthy young individuals that met the recommended physical activity guidelines, just 14 days of increased sedentary behaviour resulted in small but significant reductions in fitness that were accompanied by reductions in muscle mass and increases in body fat. Such changes can lead to chronic metabolic disease and premature mortality. The results emphasise the importance of remaining physically active, and highlight the dangerous consequences of continuous sedentary behaviour.
‘Our day-to-day physical activity is key to abstaining from disease and health complications. People must avoid sitting for long periods of time.’
The authors say the results emphasise the importance of day-to-day physical activity. However, there are a few drawbacks. Above all, we only have access to a press release rather than the paper itself, which makes it difficult to assess how well the outcomes were measured and to judge the quality of the study, though we can see that the study size is very small.
What would be interesting to see is how easily these changes are reversed once activity is resumed. The news headlines talk about a two-week holiday drastically increasing risk of chronic diseases and early death, yet there appears to be no mention in the study of the long-term effects of this break.