Bed rest study shows dangers of long-term inactivity for blood sugar levels

Bed rest study shows dangers of long-term inactivity for blood sugar levels
© shutterstock/Marcos Mesa Sam Wordley

A study involving 20 men lying in bed for two months shows the negative impact of long-term inactivity on blood sugar levels.

The University of Bath researchers studied the effects of long-term inactivity on the body’s metabolic health. A team led the research from the Centre for Nutrition, Exercise and Metabolism, as part of a European Space Agency (ESA) bed rest study. They found that inactivity increases blood sugar levels even if food intake is reduced.

The researchers monitored 20 young, fit and healthy make participants for 60 days whilst they stayed in bed with their feet above their heads to understand how blood sugar levels and a range of health measures are affected by inactivity. The individuals remained in bed whilst they ate, showered, and went to the toilet.

The results are published in the journal Clinical Nutrition.

Metabolic health and activity levels

The researchers focused on the participants’ metabolic health, which is how well the body controls blood sugar levels.

Previous work from the Bath team found that exercise, even in short bursts, has a major short-term impact on blood sugar levels. However, in this new study, the team wanted to understand more about what happens when there is no physical activity or movement over weeks and months. The 20 participants were fed a reduced-calorie diet to compensate for the reduced levels of physical activity to stop them from gaining weight.

The study showed that even when food intake was reduced to match participants’ much lower energy expenditure during bed rest, inactivity negatively and profoundly impacted their blood sugar levels.

How are blood sugar levels impacted?

Average blood sugar levels in the participants increased by around 6% during the day and by 10% at night. Their ability to dispose of blood sugar also decreased by 24%. Furthermore, the participants struggled to control their blood sugar, an important risk factor in developing conditions such as cardiovascular disease.

The reduced calorie intake did prevent participants from experiencing even higher blood sugar levels. The researchers believe that if the participants ate the same amount as normal, given the reduction in the ability to dispose of sugar, their blood sugar concentrations would have risen even further.

Professor of Human Physiology Dylan Thompson at the University of Bath led the research. He explained: “This was a unique study in which 20 young fit and healthy men were subjected to a series of tests over the course of nearly two months during which time they stayed in bed with no physical activity. Such bed rest studies are used to examine deconditioning as a model for microgravity, and this was one of the longest.

“Our results reveal that the withdrawal of physical activity profoundly impacts physiological health over and above the impact of controlling diet. Whilst the changes were not as large as would be expected had participants maintained the same calorie intake as before the study, because of their inactivity, there was a real increase in participants’ blood sugar levels and a reduction in their ability to take up and use sugar. This shows that adjusting diet alone sadly cannot overcome all the negative effects from reducing physical activity – even if you manage to avoid gaining weight.”

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