Effects of Caffeine in Hydration and Energy Metabolism
Condition: Caffeine
Study type: Interventional

Summary: 
      The main purposes of this randomized cross-over trial are to characterize and compare the
      effects of a moderate dose of caffeine intake in healthy physically active males on hydration
      and energy metabolism specifically:

        1. Total body water and its compartments (intracellular and extracellular) assessed by by
           dilution techniques, and hydration state by urine specific gravity;

        2. Total energy expenditure by double labeled water, resting energy expenditure by indirect
           calorimetry, and physical activity energy expenditure;

        3. Energy expenditure in physical activity of daily living, in particular duration and
           intensity of activity.

        4. If the changes occurred between placebo and caffeine ingestion on the main outcomes were
           dependent on specific covariates, namely body composition and dietary intake.
    

Detailed description: 
      Although the effect of caffeine on hydration status, usually assessed by a urine specific
      gravity test (USG) has been extensively studied no research has been conducted to analyze its
      effects on total body water and its compartments using reference methods. In addition some
      uncertainty still remains about the influence of caffeine ingestion on hydration due to
      methodological limitations, specifically the use of less valid techniques for total-body
      water assessment, small sample size, and the lack of control for potential confounding
      factors. The information above specifically the methodological gaps mentioned and an
      inadequate experimental design lead us to further understand the effect of a moderate dose of
      caffeine in total body water (TBW) and its intra (ICW) and extracellular (ECW) compartments
      in non-caffeine consumers during a short-term period (4 days). Additionally, though caffeine
      effects on energy expenditure has been studied, its influence on physical activity (PA)
      during free-living conditions using gold standard and objective measures of PA is limited.
      Therefore, we also investigated the impact of a moderate dose of caffeine on resting energy
      expenditure (REE), PA energy expenditure (PAEE), total energy expenditure (TEE), and daily
      time spent in sedentary (DTSS), light (DTSL), moderate (DTSM), and vigorous (DTSV) intensity
      activities in non-obese physically active males. To overcome the methodological gaps in
      previous studies we assessed dietary intake and objective measures of physical activity
      throughout the experimental trial to assure that the same diet and physical activity patterns
      were maintained. Also it was analyzed if the effect of caffeine was independent of body
      composition, assessed by dual-energy x-ray absorptiometry.

      To perform this research study, a total of 30 non-smoker males, low caffeine users (<100
      mg/day), aged 20-39 yrs [body mass (BM): 72.7 ± 8.8 kg; Height: 1.77 ± 0.07 m] were followed
      in a double-blind crossover experimental design with two conditions in a random sequence:
      caffeine (5 mg per kg of BM/day) and malt-dextrine as placebo, both through capsules.
      Conditions lasted for 4 days with a 3-day washout period.

      Evaluations were performed at baseline (visit-1), end of condition 1 (visit-2), and end of
      condition 2 (visit-3). Fat and fat-free masses (FFM) were assessed by dual energy x-ray
      absorptiometry. TBW and ECW were determined by dilution techniques (deuterium and bromide,
      specifically) while ICW was calculated as the difference between TBW and ECW (Schoeller et
      al., 1980. Total body water measurement in humans with 18O and 2H labeled water. Am J Clin
      Nutr 33:2686-2693). TEE was assessed using doubly labeled water technique by administrating
      two stable isotopes 2H (deuterium) and 18O (oxygen 18) with a respective dose of 0.1 g / kg
      and 1.8 g / kg of body water (Schoeller DA, van Santen E, 1982. Measurement of energy
      expenditure in humans by doubly labeled water method. J Appl Physiol 53:955-959). REE was
      assessed by indirect calorimetry and PAEE calculated as [TEE-(REE+0.1TEE)]. An accelerometer
      (ActiGraph, GT1M model, Fort Walton Beach, Florida) was used to estimate DTSS, DTSL, DTSM,
      and DTSV. The cutoff values used to define the intensity of physical activity and therefore
      to quantify the mean time in each intensity (sedentary, light, moderate or vigorous) for
      persons aged 18 years or older were: sedentary: < 100 counts/min; light: 100-2019 counts/min;
      moderate: 2,020-5,998 counts/min (corresponding to 3-5.9 METs); vigorous: ≥ 5999 counts/min
      (corresponding to ≥ 6 METs) (Troiano et al. Physical activity in the United States measured
      by accelerometer. Med Sci Sports Exerc. 2008;40:181-8).
    

Intervention name(s): Caffeine; Placebo
Intervention type(s): Drug; Drug
Intervention description(s): 5 mg/ kg of body weight (capsules), twice a day (morning and afternoon), during 4 days.; Malt dextrin (5 mg/kg body mass) twice a day during 4 days
Intervention MeSH terms: Caffeine
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Prevention
Keywords: Total; Intra and Extracellular Water; Energy Expenditure, Physical Activity; Body Composition; Dilution Techniques