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A recent study conducted by the National PET Centre and the UKK Institute suggests that even light physical activity is associated with better metabolic flexibility in sedentary, overweight adults at risk of diabetes. Conversely, prolonged sitting may impair the efficient utilization of nutrients.

Lifestyle habits influence fat and sugar metabolism. Limited movement and excessive sitting often lead to reduced metabolism and energy expenditure, resulting in weight gain if energy intake exceeds expenditure.

Additionally, impaired metabolic flexibility, reflecting the ability to utilize dietary energy sources for energy production, may contribute to this phenomenon.

"Under normal fasting conditions, the body burns more fat than carbohydrates. A healthy body can also switch between using fats and carbohydrates depending on the availability in the bloodstream. This reflects good metabolic flexibility," explains Taru Garthwaite, a doctoral researcher at the University of Turku.

"Conversely, with impaired metabolic flexibility, the body cannot efficiently utilize energy nutrients, leading to elevated blood sugar and fat levels. Moreover, excessive fat and sugars may be stored, contributing to central obesity," she adds.

Central obesity and disrupted fat and sugar metabolism are closely linked to reduced insulin sensitivity, increasing the risk of type 2 diabetes and cardiovascular diseases.

"While exercise is known to be beneficial for weight management and reducing diabetes risk, the associations between daily physical activity measured by a motion sensor and sitting time with metabolic flexibility have not been previously studied," notes Garthwaite.

The study, conducted by the National PET Centre and the UKK Institute, investigated the relationships between sedentary behavior, physical activity, and fitness with metabolic flexibility in sedentary, overweight adults at risk of type 2 diabetes and cardiovascular diseases. Metabolic flexibility was assessed based on oxygen and carbon dioxide levels during rest, insulin stimulation, and a bicycle fitness test.

Movement and Sitting Linked to Fat Metabolism

The study found that overall physical activity and even light physical activity were associated with better metabolic flexibility. Moreover, longer standing time and higher daily step counts were linked to increased fat burning during fasting.

Conversely, prolonged sitting was associated with reduced fat burning and metabolic flexibility. Additionally, those who sat for more than 10 hours a day exhibited poorer metabolic flexibility compared to those who sat less. While physical activity or sitting time did not correlate with carbohydrate utilization, better aerobic fitness was associated with increased carbohydrate burning.

"This suggests that reducing sitting time and increasing even light physical activity may be beneficial for regulating energy metabolism, especially concerning fat metabolism," says Garthwaite.

"However, these findings may apply mainly to individuals with low physical activity levels and already elevated weight and diabetes risk. Healthy individuals may not derive additional benefits from these measures, and enhancing metabolism likely requires increased physical activity levels or higher-intensity exercise," she points out.

However, this cross-sectional study cannot establish causality. Researchers are currently investigating how reducing daily sitting time actually affects metabolic flexibility over a six-month study period.

The study has been published in the American Journal of Physiology-Endocrinology and Metabolism.

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