Physical exercise alone generally fails to produce meaningful weight loss in obese individuals, and reduced non-exercise activity has been suggested to explain this observation.

Daniel Lark, PhD, and colleagues explored how interactions between exercise (voluntary wheel running) and non-exercise activity (“off-wheel” activity) affect energy balance in mice.

They continuously monitored mouse behavior, energy intake, and energy expenditure with locked running wheels (no exercise) for 4 days, followed by unlocked running wheels for 9 days.

The researchers reported in the journal Diabetes that when running wheels were unlocked, mice engaged in voluntary exercise, which increased their energy expenditure and resulted in a negative energy balance. However, wheel running caused mice to decrease their off-wheel activity, such as roaming behavior. This reduction in non-exercise activity blunted the negative energy balance.

The study is the first to report an independent contribution of non-exercise physical activity to energy expenditure and energy balance in mice. By doing so, the study provides a model to further study mechanisms that regulate body weight.