Extra sessions of exercise during the ‘critical period’ when early-teens are most vulnerable to the onset of type 2 diabetes could help safeguard against the condition.

A study from the University of Exeter published in the journal Diabetologia found that physical activity provides the greatest benefits to adolescent insulin resistance – a risk factor for type 2 diabetes – when the condition peaks at age 13, but provides no benefit to it at age 16.

Given that the fitness levels of English schoolchildren were recently shown to be at a record low, the new findings could help to design more effective interventions for children at risk of diabetes by targeting the early-teens.

The researchers measured insulin resistance, a condition which leads to high blood sugar and is a precursor to type 2 diabetes, in the same 300 children every year from age 9 through to age 16. They set out to determine when and to what extent physical activity in children impacts on insulin resistance and other markers of metabolic health.

The results showed that instances of insulin resistance were 17 per cent lower in the more active adolescents at age 13 independently of body fat levels. However, this difference diminished progressively over the next three years and had disappeared completely by age 16, when insulin resistance levels were much lower.

Dr Brad Metcalf, a senior lecturer in Physical Activity and Health at the University of Exeter said the findings have implications for future actions designed to reduce the insulin resistance of children.

“Our study found that physical activity reduced this early-teenage peak in insulin resistance but had no impact at age 16,” said Dr Metcalf.

“A reduction in this peak could lessen the demand on the cells that produce insulin during this critical period, which may preserve them for longer in later life. We’re not saying 16-year-olds don’t need to be physically active, there are other health benefits to be gained from being active at all ages.”

Held up as a key prevention measure in tackling diabetes, exercise can help manage the condition for existing sufferers. Previous research has found that exercise in any form can play a key role in helping diabetics to reduce body fat and control glucose, even among so-called ‘non-responders.’