Postprandial Metabolism in Healthy Young Subjects
Condition: Postprandial Period; Biomarkers; Fasting
Study type: Interventional

Summary: 
      This study aims to describe the dynamic changes in nutritional biomarkers in the blood during
      the postprandial period, i.e. the time period from the last meal and into the fasting state.
      In total 36 healthy, young men and women will be recruited in Bergen, Norway, and after
      receiving a standardized breakfast meal they will consume only water for the next 24 hours.
    

Detailed description: 
      Throughout the day, humans switch back and forth between the fed, postprandial (after a
      meal), and the postabsorptive (fasting) metabolic state. This is followed by a shift in fuel
      utilization from primarily using glucose to predominantly rely on β-oxidation of fatty acids.
      Consequently, circulating concentrations of biomarkers may fluctuate in response to this
      changing metabolic state. Much is known about the hormonal and metabolic effects of fasting,
      including lower insulin secretion, increased release of free fatty acids from adipose tissue,
      increased ketogenesis, glycogen breakdown, and activated gluconeogenesis. However, less is
      known about the effect on other biochemical markers in the postabsorptive period.

      When evaluating nutritional biomarkers, both in clinical practice and in research, it is
      common practice to distinguish between fasting or non-fasting blood samples, based on time
      since the last meal. The extent to which different biomarkers are influenced by fasting
      status vary, and accordingly, several diagnostic cutoffs, e.g. plasma glucose for diabetes
      diagnosis, vary according to whether the sample was fasting or not. However, as the
      adaptation to fasting is a gradual process, it is expected that any changes in biomarker
      concentrations are also gradual. Further, as circulating metabolite concentrations are
      determined as a result of input (intestinal absorption and release from tissues), metabolism,
      and removal (utilization, storage, and excretion), we cannot reasonably assume that these
      changes are linear.

      A few previous studies have aimed at describing the dynamics of fasting metabolism,
      demonstrating that the circulating metabolome changes during prolonged fasting in a dynamic
      manner. However, as data collection started after an overnight fast period, these studies do
      not provide data on the initial postprandial period and the adaptation to the fasting state.
      This study will extend the knowledge on the dynamics of human postprandial metabolism, by
      monitoring circulating concentrations of biomarkers during the 24 hours after a standardized
      breakfast meal. The investigators aim to capture the adaptation period from the fed to the
      fasting state and provide time-resolved data on a broad range of nutritional biomarkers.

      Enrolled participants will attend the study center after an overnight fast, following a
      standardized evening meal consumed 12 hours before attendance. Anthropometric measurements
      (body weight, height, waist circumference, and body composition) will be taken in the fasting
      state, and a fasting blood sample will be drawn. After completing a standardized breakfast
      meal, the participants will remain at the study center for 12 hours, and blood will be
      frequently collected at specified time points. The participants will return to the study
      center the following morning for a final 24h fasting blood sample.
    

Intervention name(s): Fasting
Intervention type(s): Other
Intervention description(s): After the standardized breakfast meal, all participants will only consume water for 24 hours
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Other
Keywords: Postprandial metabolism; Nutritional biomarker; Fasting