Effects of Time-restricted Eating on Nutrient Absorption in Healthy Adults
Condition: Digestibility
Study type: Interventional

Summary: 
      This 2-period, crossover, controlled-feeding trial will investigate the effects of early
      time-restricted eating (8am-2pm), compared to a control eating timeframe (8am-8pm), on energy
      and macronutrient digestibility, the thermic effect of food (TEF), postprandial blood
      metabolites, 24 h glucose concentrations, glycemic variability, intestinal hydrogen gas
      production, gastrointestinal transit time, and microbiome composition. This study will also
      seek to determine factors that may predict intestinal absorption efficiency (i.e.,
      digestibility) including the microbial composition of stool, fasting and postprandial
      metabolomics, gastrointestinal transit time, thermic effect of food, 24 h glucose
      concentrations and variability, and hydrogen gas production.
    

Detailed description: 
      The obesity epidemic is well documented, and despite a complex etiology influenced by
      genetic, physiological, psychological, social, behavioral, and environmental factors, obesity
      seems to be the result of energy imbalance, where energy intake exceeds energy expenditure,
      regardless of the internal and external influences. Studies aiming to quantify and manipulate
      modulators of energy balance, including gastrointestinal (GI) energy absorption rates (i.e.,
      digestibility), are crucial for reducing the incidence of overweight and obesity and
      improving overall human health. Despite considerable interindividual variability in the
      amount of ingested energy that is absorbed (~87-98% of ingested energy) by the
      gastrointestinal tract, generalized equations are used to calculate individual energy intake
      requirements, and the factors that contribute to such variability, including meal-timing, are
      largely unknown.

      The proposed study seeks to determine the effects of restricting the eating window to 6-h
      (early time-restricted eating) as compared to a control eating window of 12 h on energy and
      macronutrient digestibility, thermic effect of food (TEF), postprandial blood metabolites
      (triglyceride, insulin, glucose, fructose, galactose, inositol, and sorbitol), 24 h glucose
      concentrations and glycemic variability, intestinal hydrogen gas production, microbiome
      composition, and gastrointestinal transit time in response to a controlled, energy balanced
      diet. In addition, this project will determine whether energy digestibility can be predicted
      from biological and physiological factors such as gut microbiota composition,
      gastrointestinal transit time, 24-h glucose concentrations, and postabsorptive and
      postprandial metabolomic profiles.

      Participants will be randomized to early TRE (6-h feeding window, 8am-2pm) or a control
      eating schedule (12-h feeding window, 8am-8pm) and consume a controlled, energy balance diet
      (breakfast, lunch, dinner, snacks, and beverages) for 9 consecutive days before crossing over
      to the other intervention after at least a 3-wk washout for females (to control for hormonal
      fluctuations) and at least a 2-wk washout for males. Participants will collect stool and
      urine during each feeding phase. Gross energy content (heat combustion by bomb calorimetry)
      of the diet, stool, and urine samples will be used to calculate energy digestibility (diet
      gross energy - stool gross energy) and metabolizable energy. Factors that may mediate and/or
      predict energy digestibility efficiency, including gastrointestinal microbial composition,
      transit time, and gas production, fasting and postprandial metabolites, continuous glucose
      concentrations, and thermogenesis will be assessed.
    

Intervention name(s): weight maintenance diet (WMD)
Intervention type(s): Other
Intervention description(s): A diet meeting the participant's weight maintenance energy needs will be provided.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: The study is a randomized, crossover, controlled feeding study design consisting of two 9-d weight maintenance diet periods separated by at least 3 weeks.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: stool energy loss; digestibility; intestinal absorption; overweight; microbiome; metabolomics; energy balance