Nutrition Trial on the Glycaemic Response to High GI Meals Consumed at Morning vs. Evening-The ChroNu Study
Condition: Healthy
Study type: Interventional

Summary: 
      Several studies suggest that meal timing plays an important role in the development of
      obesity and metabolic diseases. Especially in the evening, a high consumption of
      carbohydrates, which greatly increase blood glucose levels (i.e. unfavourable carbohydrates
      with a higher glycaemic index (GI)), has been found to adversely affect glycaemic response.
      However, avoidance of (unfavourable) carbohydrate consumption appears to be particularly
      problematic for young adults due to its interference with the timing of social life and their
      chronotype. The chronotype describes individual differences in sleep timing on free days and
      is most delayed around the age of 20. Young adults are thus prone to be exposed to a dietary
      misalignment when socially determined schedules, such as early lectures at universities,
      collide with their biologically determined later chronotype.

      Therefore, it is hypothesized that dietary misalignment among young adults has detrimental
      short-term effects on the glucose metabolism.

      In this nutrition trial, dietary misalignment is induced by providing the same meal rich in
      carbohydrates with a high glycaemic index (GI) on two separate days at different times:
      breakfast at 7:00 is assumed to reflect a schedule potentially inducing dietary misalignment
      among later chronotypes. Vice versa, providing this meal at dinner (20:00) may cause dietary
      misalignment among earlier chronotypes.

      Adverse glycaemic responses are expected when the high GI meal is consumed at a time which is
      deviating from the schedule of the individual chronotype. A regular increase in postprandial
      glycaemia due to constant dietary misalignment may be important in the development of
      metabolic diseases.
    

Detailed description: 
      To address the hypothesis that dietary misalignment among young adults has detrimental
      short-term effects on glucose metabolism, participants will consume a meal rich in high GI
      carbohydrates on two separate days either at breakfast (7:00) or at dinner (20:00). Glycaemic
      responses will be monitored by a continuous glucose monitoring device (CGM) (G6, Dexcom,
      Inc., San Diego, CA). The CGM electrochemically measures subcutaneous interstitial glucose
      concentrations of each participant during the whole study. A blood glucose meter will be used
      to verify the functionality of the CGM (CONTOUR®NEXT ONE).

      The caloric content of the meals will be tailored to the energy needs of the participants
      based on their age, sex and anthropometric measurements. Participants will be requested to
      consume the meals without any break. During the controlled nutrition trial, participants will
      be asked to abstain from alcohol consumption and heavy exercise and not consume any food in
      addition to that provided or drinks that should be explicitly avoided.

      To objectively corroborate their chronotype participants will be asked to wear an
      accelerometer (E4 wristband, Empatica) attached to the wrist during the controlled nutrition
      trial. Moreover, participants are asked to record their bed times, meal timings, daily
      routines, and physical activities during the trial. On day 1 and day 8, anthropometric
      measurements will be performed to compare the body composition (Bioimpedance Analysis, SECA
      mBCA) before and after the controlled nutrition trial. On day 4, fasting blood samples will
      be collected. Before the controlled nutrition trial will start, questionnaires on daily
      routines, food frequency, and chronotype will be carried out.

      The chronotype is defined as mid-sleep point and assessed by the Munich Chronotype
      Questionnaire, which is a validated questionnaire. Earlier and later chronotypes will be
      defined as 20% of the participants with each the earliest and later mid-sleep points among
      the participants of the ChroNu cohort.
    

Intervention name(s): Glycaemic response to high GI carbohydrates consumed at morning versus evening meals.
Intervention type(s): Other
Intervention description(s): Controlled nutrition trial on the glycaemic response to morning and evening meals with high glycemic index carbohydrates among students with early and late chronotypes.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: 60 participants will be invited of which 20 participants with an earlier and 20 participants with a later chronotype are expected to finish the study. Participants will consume a meal rich in carbohydrates with a high GI on two separate days at different times. Hence, participants are randomly assigned to one group stratified by chronotype: intake of a meal with a high GI on day 5 either in the morning or in the evening. On day 7, meal timing of the high GI meal is switched. Following a 3 - day observational part on "free days", the controlled nutrition trial will last 4 days: run - in (day 4), high GI meal for breakfast/dinner (days 5 / 7), and wash - out (day 6). The trial is a two-arm cross-over study in which each participant serves as his / her own control to account for inter-individual variations in diurnal glycaemic responses.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: chronotype; social jetlag; glycaemic response; glycaemic index; continuous glucose monitoring; body composition