The purpose of this study is to evaluate the acute impact of ingesting individual and combined dosages of caffeine and paraxanthine in comparison to placebo on changes in resting metabolic rate, perceived levels of affect, and markers of lipolysis.

The study will be conducted using a randomized, double-blind, placebo-controlled, crossover study design. Approximately 10 healthy men and 10 healthy women between the ages of 18 - 39 years of age will be recruited to participate in this study. Prior to beginning the study, all participants will sign an IRB-approved informed consent document and complete a healthy history questionnaire to determine study eligibility. All participants will report to the laboratory for all study visits between 0600 - 1000 hours. Prior to each of the seven study visits, participants will be asked to abstain from exercise, tobacco, nicotine, and alcohol for 24 hours and observe an overnight (8 - 10 hours) fast including caffeine. Study visit 1 will be a screening visit where participants will first sign an IRB-approved informed consent document. To determine eligibility, participants will then complete a health and medical history form and have their height and weight assessed along with their resting heart rate and blood pressure. If determined eligible, study participants will allowed to exercise within 24 hours of each study visit. On one occasion prior to study visit 1, study participants will be required to record their food and fluid intake for the three days prior to each study visit and instructed to replicate this diet prior to each visit. To assist in replicating their food intake, participants will be given pre-packaged frozen meals of their choosing. All meals will provide similar amounts of energy, carbohydrates, fats, and proteins. Participants will be instructed to follow an overnight fast whereby no food or fluid with calories will be consumed for the 8 to 10-hour period prior to each study visit. Water intake will be encouraged during this time for appropriate hydration status. Upon arrival for each subsequent study visit, participants will again have their body mass determined and they must be determined to be weight stable (defined as having a body mass within 2% of their previous study visit body mass). Resting heart rate, blood pressure, and body composition will then be assessed (only study visit 2) using a bio-electrical impedance analyzer (BIA). After assessment of body mass, resting heart rate, and resting blood pressure, study participants will donate their first of six venous blood samples. From there, participants will complete a series of assessments evaluating various perceptual indicators using the profile of mood states (POMS) and anchored 100-mm visual analog scales. Finally, participants will then have their resting metabolic rate determined using a metabolic cart. Upon determination of baseline resting metabolic rate, participants will be assigned in a randomized, double-blind, placebo-controlled, crossover fashion to ingest one of seven supplement conditions. One condition will be a non-energetic placebo (maltodextrin) while the other six supplemental conditions will be a 200 mg dose of caffeine, 100 mg paraxanthine, 200 mg paraxanthine, 300 mg paraxanthine, a combination of caffeine (200 mg) + paraxanthine (200 mg), and a 200 mg dose of 1-methylxanthine. All supplements will be orally ingested with 8 fluid ounces of cold tap water. The order of administration for all interventions will be randomized using a random allocation software to ensure randomization and to avoid order effects. After ingestion, participants will complete all assessments in an identical fashion 30, 60, 90, 120, and 180 minutes after ingestion of their assigned supplement. All study visits will take place between 0600 - 1000 hours. It is anticipated that follow-up study visits will be scheduled 3 - 7 days apart from each other after all dietary and exercise controls have been observed.

Inclusion Criteria:

• All participants will be between the ages of 18-39 years
• Participants will be healthy and free of disease as determined by evaluation of a - medical history
• All participants will be required to abstain from taking any additional forms of nutritional supplementation (pre-workouts, creatine, beta-alanine, thermogenic supplements, etc.) for four weeks prior to beginning this study and for the entire duration of the study
• Participant's report accumulating at least 30 minutes of moderate exercise 3 days per week
• Currently have a body mass index between 18.5 - 25 kg/m2. Alternatively, individuals with a body mass index between 25 - 30 kg/m2 will be included in the study if body-fat percentage is below 32% for females and 25% for males.
• Not currently restricting calories or completing a dieting program
• As determined through a caffeine intake survey, participants will be moderate caffeine consumers, consuming approximately 200 mg of caffeine per day.

Exclusion Criteria:

• Those individuals less than 18 and greater than 40 years of age will be excluded. Participants younger than 18 are excluded due to necessity of parental consent. Participants greater than 40 years old are excluded due to the known changes that occur with metabolic rate as individuals achieve an age of 40 years or greater
• As indicated on a self-reported medical history, any individual who is currently being treated for or diagnosed with a cardiac, respiratory, circulatory, musculoskeletal, metabolic, obesity (defined as body mass index > 30 kg/m2), immune, autoimmune, psychiatric, hematological, neurological, or endocrinological disorder or disease will be excluded.
• Regular (>3 days/week) administration of thermogenic supplements or other weight loss aids in the past 60 days
• Participants not meeting minimum exercise guidelines (30 minutes per day, 3 days per week) or exceeding 8 hours of exercise per week will be excluded
• Daily intake of caffeine doses exceeding 300 mg/day
• Participants who do not or are not willing to abstain from alcohol, nicotine, and caffeine for 12 hours prior to each visit will be excluded
• Participants who do not or are not willing to abstain from exercise for 24 hours prior to each visit will be excluded.
• Participants who do not or are not willing to follow the prescribed dietary control leading up to each exercise bout will be excluded
• Individuals who are pregnant, nursing, or trying to get pregnant

All supplements provided to all research participants containing Caffeine, Paraxanthine, 1-Methylxanthine, or Placebo will be procured and prepared in a similar manner. All supplements are in identical capsules.