Have you ever heard, “sleep is good food”? If not, pay attention. Recent research published in Experimental Physiology finds that our sleep cycles and patterns of activity may impact the risk of type 2 diabetes and heart disease.

In a study at Rutgers University, scientists split participants into two groups according to each chronotype. They defined chronotype as the natural preference to find activity and sleep at various times. The group that found activity at night and sleep in the morning preferable became the "night owls", while the group that preferred the opposite was dubbed "early birds." The primary focus was the metabolic difference in how much each group used insulin for glucose uptake by the cells for energy use or storage. Body mass, body composition, insulin sensitivity, and breath samples were collected through advanced imaging to discover fat and carbohydrate metabolism in each group of 51 subjects in the study.

Subjects were followed for a week to evaluate their levels of activity throughout the day. Subjects ate a nutritious, calorie-controlled diet provided to them by the scientists. Subjects fasted overnight to limit the dietary impact on the results. To test fuel preference, subjects were evaluated at rest before finishing two, 15-minute sessions of exercise: one moderate, and one high intensity on a treadmill. Scientists evaluated levels of aerobic fitness via an incline challenge where the incline was raised by 2.5% every two minutes until the subject reached a level of exhaustion.

Early birds were more active during the day and used more fat as an energy source during exercise. They had higher levels of cardiovascular fitness compared to night owls. Early birds also had better insulin sensitivity.

The night owl groups preferred to be active later in the day and used less fat as energy throughout exercise, and at rest. These individuals had less ability to use fat stores for energy, possibly leading to fat stores building up in the body. They were also more insulin resistant, and their bodies used more carbohydrates for energy than fat. The night owl’s altered capacity to respond to insulin raises the risk for type 2 diabetes and cardiovascular disease.

Lead author Professor Steven Malin of Rutgers University stated, "The differences in fat metabolism between 'early birds' and 'night owls' shows that our body's circadian rhythm (wake/sleep cycle) could affect how our bodies use insulin. A sensitive or impaired ability to respond to the insulin hormone has major implications for our health. This observation advances our understanding of how our body's circadian rhythms impact our health. Because chronotype appears to impact our metabolism and hormone action, we suggest that chronotype could be used as a factor to predict an individual's disease risk."

More research is needed to evaluate the association between chronotype, physical activity, and metabolic adaptation to find if exercising earlier in the day has the best health benefits.

What can you advise your clients who are at risk for type 2 diabetes and heart disease?

• Aim for seven to eight hours of sleep each night. Sleep impacts cortisol levels, which raises the risk of heart disease and diabetes when cortisol is elevated.

• Stop eating after dinner. Most people are less active in the evening, and therefore less likely to use calories eaten later at night.

• Walk or do other physical activity earlier in the day. There’s less risk of excuses getting in the way of exercise.

• Limit added sugars in your diet.

• Reduce saturated and trans-fat to keep lipids in check.

• Include foods high in soluble fiber to help manage blood sugar and cholesterol. Fibrous foods such as apples, barley, beans, and oats are the best examples.

• Reduce your red meat and processed meat intake.

By Lisa Andrews, MEd, RD, LD

References:

Antza, C., Kostopoulos, G., Mostafa, S., Nirantharakumar, K., & Tahrani, A. (2022). The links between sleep duration, obesity and type 2 diabetes mellitus. Journal of Endocrinology, 252(2), 125–141. https://doi.org/10.1530/joe-21-0155

Malin, S. K., Remchak, M. M. E., Smith, A. J., Ragland, T. J., Heiston, E. M., & Cheema, U. (2022). Early chronotype with metabolic syndrome favours resting and exercise fat oxidation in relation to insulin?stimulated non?oxidative glucose disposal. Experimental Physiology. https://doi.org/10.1113/ep090613

Misra, R., Balagopal, P., Raj, S., & Patel, T. G. (2018). Red Meat Consumption (heme iron intake) and risk for diabetes and comorbidities? Current Diabetes Reports, 18(11). https://doi.org/10.1007/s11892-018-1071-8