It’s not only what you do, but when you do it. Researchers call it “chronomedicine,” and it’s one of the new frontiers of health research. It’s the study of the connection between the circadian clock and human health. (Circadian rhythms describe the circle of physical and mental changes that the body experiences throughout the 24 hours of a day). As an example of the emerging research in this field, three scientists who study circadian rhythms won the 2017 Nobel Prize in Physiology and Medicine for the discovery of a “clock” protein that, like a clock, builds up in cells at certain times of the day and breaks down at other times.
Now a new study from researchers at Northwestern University in Chicago presented at the ENDO 2021 meeting has applied chronomedicine to the subject of developing type 2 diabetes. Their report indicates that people who eat breakfast before 8:30 in the morning have a lower risk of diabetes.
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The researchers studied data derived from what’s known as the National Health and Nutrition Examination Survey, or NHANES. NHANES is a series of studies launched in the early 1960s by the U.S. Centers for Disease Control and Prevention (CDC). It combines both personal interviews and physical examinations to assess the health and nutritional status of American adults and children and it’s become a major source of health statistics in the United States.
The authors of the new study retrieved data on 10,575 adults who had participated in NHANES. The researchers were interested in not only how many hours per day the subjects spent eating (what’s known as eating duration), but also what time of day the subjects began eating. Earlier research has shown that time-restricted eating (eating fewer hours per day) seems to relate to improvements in metabolic health, which is defined as having normal levels of blood sugar, HDL cholesterol, triglycerides and blood pressure, conditions that can affect a person’s risk of developing diabetes, heart disease and stroke. For this new study, however, the researchers wanted to explore whether eating earlier in the day might also affect metabolic health. According to lead researcher Marriam Ali, MD, “With a rise in metabolic disorders such as diabetes, we wanted to expand our understanding of nutritional strategies to aid in addressing this growing concern.”
The study authors divided the subjects into three groups: those who ate only during a period of less than 10 hours (this amount qualifies as “intermittent fasting”), during a period of 10 to 13 hours, and during a period of more than 13 hours per day. Then the researchers created six subgroups depending on when the subjects began to eat (before or after 8:30 a.m.).
Eating before 8:30 a.m., the researchers concluded, was the factor related to the widest health outcomes. The subjects who began eating earlier had better blood sugar levels and better insulin resistance that those who began eating later. As Dr. Ali put it, “We found people who started eating earlier in the day had lower blood sugar levels and less insulin resistance, regardless of whether they restricted their food intake to less than 10 hours a day or their food intake was spread over more than 13 hours a day.”
And she added, “These findings suggest that timing is more strongly associated with metabolic measures than duration, and support early eating strategies.” The study might be especially relevant to advocates of intermittent fasting, which has become more popular in recent years. Some schedules of intermittent fasting, which typically limits eating duration to 10, or even 8, hours a day require eating the first meal at noon.
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