Going to bed later is linked with obesity in people with type 2 diabetes, and the main factor that drives this relationship is eating breakfast later.
This was the conclusion of a new study now published in the journal Diabetic Medicine.
Prof. Reutrakul suggests that eating later causes a shift in the biological clock that regulates day-night patterns. Other studies have proposed that this can disrupt energy metabolism.
Type 2 diabetes accounts for the vast majority of diabetes cases.
It develops when the body does not respond properly to insulin, which is a hormone made in the pancreas. It helps cells to take in and use blood sugar for energy.
The pancreas tries to compensate by making more insulin, but eventually, it cannot keep up. This may result in a condition called hyperglycemia, or high blood sugar, which can lead to severe health problems.
The global obesity epidemic is considered the main reason that rates of diabetes have risen dramatically in the past 20 years.
In the study paper, Prof. Reutrakul and colleagues refer to research that indicates that a preference for later bedtime and meal times is linked to obesity but note that evidence of this is “lacking in people with type 2 diabetes.”
For the new study, the researchers investigated how the following variables may relate to each other in people with type 2 diabetes:
- timing of meals
- patterns of getting up and going to bed early and late, which the authors refer to as “morningness-eveningness preference”
- body mass index (BMI), which was used as a measure of obesity
In addition, the researchers ran a “mediation analysis” to determine whether morningness-eveningness preference “had a direct effect on BMI,” or whether timing of meals might be driving the effect indirectly.
The participants were 210 working-age Thailand residents with type 2 diabetes who were not working shifts.
The data on morningness-eveningness patterns came from answers that they gave in a standard questionnaire called Composite Scale of Morningness (CSM).
The researchers assessed morningness-eveningness preferences from answers to questions about: preferred waking up and going to bed times, the preferred time of day for taking exercise, and preferred time of day for working, reading, and other mental activities.
The CSM yields a score that ranges from 13 for “extreme evening preference” to 55 for “extreme morning preference.” The researchers decided that scoring under 45 indicated an evening preference and over 45 indicated a morning preference.
From interviews, further questionnaires, and physical exams, the team also collected data about: meal timing, daily intake of calories, duration and quality of sleep, and weight and height (to calculate BMI).
The results showed that, on average, the participants:
- slept for 5.5 hours each night
- consumed 1,103 calories per day
- had a BMI of 28.4 (which is in the overweight range)
In addition, the scientists found that 113 participants had a preference for mornings (CSM score over 45) and breakfasted between 7:00 and 8:30 a.m., while the remaining 97 showed a preference for evenings (CSM score under 45) and breakfasted between 7:30 and 9:00 a.m.
They also found that those with a preference for mornings ate all their meals earlier — not just their breakfasts, but also their lunches, dinners, and final meals.
Further analysis revealed that a greater evening preference was linked to having a higher BMI. However, calorie intake and timing of lunch and dinner was not linked to a higher BMI.
The mediation analysis showed that a preference for mornings was linked to having an earlier breakfast and a BMI that is 0.37 lower.
As the researchers conclude, “Late breakfast time mediated the relationship between morningness-eveningness preference and BMI.”
“Later breakfast time is a novel risk factor associated with a higher BMI among people with type 2 diabetes. It remains to be investigated if eating breakfast earlier will help with body weight in this population.”
Prof. Sirimon Reutrakul