Morning person or morning grouch? For type 2 diabetes and heart disease, it could play a role which circadian rhythm suits you better: people who like to stay up late use fat less well for energy. This poses a risk to weight and metabolism.
Researchers have studied the metabolism of morning and evening people. It turned out that early risers consumed more fat as an energy source than evening people, both at rest and in short training sessions of medium and high intensity. The early risers were also more sensitive to insulin. Evening people, on the other hand, used carbohydrates more as an energy source, and their bodies had to release more insulin to lower blood sugar levels, the scientists report in the journal Experimental Physiology. The latter indicates a greater risk of type 2 diabetes.
It is not yet known why the metabolism differs depending on the daily rhythm. Prof Steven Malin of Rutgers University in New Jersey said: “The differences in lipid metabolism between ‘larks’ and ‘owls’ indicate that circadian rhythms may affect how the body uses insulin. We also found that early risers are more physically active and fitter than evening people, who tend to be more sedentary throughout the day.”
The researchers divided 51 people into two groups according to their circadian rhythms and measured their body mass and composition using advanced imaging. They examined the metabolism using breath samples. During the study, which ran over a week, study participants ate a controlled diet to minimize the impact of diet on results.
Which: DOI 10.1113/EP090613