Are you at higher risk of diabetes or heart attack if you’re a night owl or an early riser?
A few months ago, an investigation published in “PNAS” concluded that you should sleep with the blinds closed to avoid the risk of heart disease and diabetes.
The reason is that the likelihood of suffering from these pathologies increases with exposure to light during rest, increasing insulin resistance the next morning.
Our activity patterns and sleep cycles can affect our risk of disease. Faced with this reality, a team of researchers from Rutgers University in New Jersey (USA) wondered if this risk increases if a person is an early riser or a night owl.
Well, the research published today in “Experimental Physiology”, found that people who are “night owls” may have a higher risk of type 2 diabetes and heart disease than “morning birds.”
This is because sleep/wake cycles cause metabolic differences and change our body’s preferences for energy sources. The researchers found that those who stay up later have a reduced ability to use fat for energy, meaning that fat can accumulate in the body and increase the risk of type 2 diabetes and cardiovascular disease.
Metabolic differences refer to how well each group can use insulin to promote the uptake of glucose by cells for energy storage and use.
People who prefer to be active in the morning rely more on fat for energy and are more active during the day with higher levels of aerobic fitness than night owls.
Conversely, people who prefer to be active later in the day and night use less fat for energy at rest and during exercise.
To reach these conclusions, the researchers classified 51 participants into two groups (early and late) according to their “chronotype”: their tendency to develop physical or mental activities, depending on the time in which they are.
They used advanced imaging to assess body mass and body composition, as well as insulin sensitivity and breath samples to measure fat and carbohydrate metabolism.
Participants were monitored for a week to assess their activity throughout the day. They ate a calorie- and nutrient-controlled diet and had to fast overnight to minimize the impact of the diet on the results.
To study fuel preferences, they were tested at rest before completing two 15-minute bouts of exercise: one moderate-intensity session and one high-intensity treadmill session. Aerobic fitness levels were assessed using an incline challenge where the incline was increased by 2.5% every two minutes until the participant reached their point of exhaustion.
The researchers found that Early risers use more fat for energy both at rest and during exercise than night owls. Early risers were also more insulin sensitive.
Night owls, on the other hand, are insulin resistant, meaning their bodies need more insulin to lower blood sugar levels, and their bodies prefer carbohydrates for energy over fat.
This group’s impaired ability to respond to insulin to promote fuel use can be detrimental, indicating an increased risk of type 2 diabetes and/or heart disease.
The reason for this change in metabolic preferences between early risers and night owls is not yet known and more research is needed.
“Differences in fat metabolism between ‘morning birds’ and ‘night owls’ show that our body’s circadian rhythm can affect how our body uses insulin. A sensitive or impaired ability to respond to the hormone insulin has important consequences for our health,” said lead study author Professor Stephen Malin in a statement.
“This observation,” he continues, “improves our understanding of how our body’s circadian rhythms affect our health.” Because chronotype appears to influence our metabolism and hormone action, we hypothesize that chronotype can be used as a predictor of individual disease risk.”
“We found that too early risers are more physically active and have higher fitness levels than night owls, who are more sedentary during the day. More research is needed to examine the relationship between chronotype, exercise, and metabolic adaptation to determine whether exercise earlier in the day has greater health benefits.”
