Exercise and Sport Sciences Reviews: 2020 Paper of the Year Commentary

Editor’s note: The 2020 Paper of the Year for Exercise and Sport Sciences Reviews was selected based on the significance and impact of the article. To read more about the award and the articles selected for the other four American College of Sports Medicine journals, seehttps://www.acsm.org/read-research/journals-bulletins

In their Perspective for Progress, Parr et al.(¹) discuss how 24-h access to energy-dense foods, combined with low levels of physical activity, influence human circadian rhythm. They propose that exercise training and dietary timing can improve health and decrease risk of chronic disease. Meal timing is important and can influence sleep/wake patterns, insulin sensitivity, core body temperature, and mental focus. They term the timing of meals, which could lead to improved metabolic health, as “chrono-nutrition.” The concept emphasizes the importance of both when individuals eat and the quality of food that is consumed.

Parr et al. first discuss the benefits of time-restricted eating (TRE), which decreases the total time individuals consume food, typically from 14 to 10 h per day of total eating time. However, they also mention that early TRE has shown beneficial effects on glycemic control; however, meal consumption would need to be completed by 1500 h, which would likely lessen adherence to the protocol. TRE that begins at 1200 h showed either no benefits or an improvement in glycemic control. TRE eating increases the time a person is in the fasted state, which can parallel some of the same responses that are seen after exercise.

The authors state, however, that the effects of exercise on cardiometabolic health far outweigh any dietary changes. They refer to epidemiological evidence on the association between poor cardiovascular fitness and all-cause mortality, more so than being obese. However, it is difficult to motivate people to begin an exercise program, if they have not done so already, and then to have them adhere to an exercise program. Only approximately 25% of individuals exercise on a regular basis. The other important aspect of physical activity is its positive influence on body composition. Aerobic training typically decreases body fat, whereas resistance training can maintain or increase muscle mass, and both can maintain bone mineral density.

The combination of consuming a healthy diet and properly timed eating, combined with physical activity, is the best scenario for maintaining overall health. Diet quality still needs to be emphasized, however. Establishing a healthy dietary intake, with properly timed eating, combined with daily physical activity will result in the greatest health benefits. Research has shown the benefits of combining a healthy diet (e.g., consuming the Mediterranean diet) with exercise on weight loss, fat loss, and improved cardiometabolic health in individuals who were overweight or obese, those with cardiovascular disease, or those diagnosed with diabetes mellitus. In addition, some work has shown these combined lifestyle changes can decrease inflammatory response and pain from knee osteoarthritis.

To summarize, Parr et al. emphasize the importance of both nutrition timing (chrono-nutrition) and exercise on overall health. They placed a greater emphasis on physical activity, mainly due to the difficultly in having people adhere to a daily exercise routine. More research is needed on the long-term outcomes of combining chrono-nutrition and exercise with respect to exercise performance and disease prevention.