Metabolic flexibility is the ability to properly switch between fat and carbohydrate stores to use for energy under different conditions (rest, feeding, exercise). Impairments in metabolic flexibility, also known as metabolic inflexibility, have been suggested to be an underlying cause of metabolic disease, like type 2 diabetes. Long-term low fluid intake may increase the risk of type 2 diabetes due to insulin resistance, a form of metabolic inflexibility. Further, low fluid intake has been shown to impair the ability to switch fuel preference during exercise.

While there is some evidence that low fluid intake may lead to impaired metabolic flexibility, more information is needed. Therefore, the purpose of this study is to evaluate the impact of hydration status on substrate preference at rest and during exercise at varying intensities (light and moderate). Further, we will examine whether biological sex and menstrual cycle phase impact hydration and metabolism under these same conditions.

The 3-arm intervention will be completed in females during both the follicular and luteal phases for a total of 13 visits including the medical screening. In males, the 3-arm intervention will be completed once for a total of 7 visits including the medical screening.

Inclusion Criteria:

• Subject is male or female
• If female, subject is not pregnant (based on self-report)
• If female, subject has stopped taking birth control medication or removed long-acting reversible contraceptive >6 months at start of the study
• If female, subject has normal menstrual cycle (21-35 days)
• If female, subject is willing to track their menstrual cycle
• If female, subject has a smartphone compatible for application to track menstrual cycle (female only) and/or wearable data (females and males)
• Subject is 18-35 years of age, inclusive
• Subject body mass index (BMI) is between 18.5-25 kg/m2
• Subject is at least recreationally active (engaged in moderate-intensity, intermittent, or steady-state exercise at least 3 days per week for at least 60 min at a time)
• Subject is accustomed to cycling for at least 60 min
• Subject does not smoke (or has quit for at least 6 months)
• Subject is not taking medication that may interfere with the study (e.g., diuretics, laxatives, or weight loss drugs)
• Subject has no health conditions that would interfere with the study as indicated on the general health questionnaire (GHQ) e.g. cardiovascular, renal, or metabolic diseases
• Subject is not actively involved in weight loss intervention (dieting and/or anti-obesity medications)
• Subject is not allergic to adhesives (e.g., medical tape)
• Subject is willing to avoid alcohol consumption 24 hours prior to visit(s)
• Subject is willing to fast overnight (~8-12 hours)
• Subject is willing to refrain from vigorous exercise for 24 hours (light physical activity only)
• Subject is willing to be shaved at patch or electrode site, if necessary
• Subject is willing to eat the exact same food the day prior to each visit to the laboratory
• Able to speak, write, and read English
• Provision of written consent to participate

Exclusion Criteria:

• Subject has participated in a clinical trial within the past 30 days
• Subject has participated in any PepsiCo trial within past 36 months
• Subject has a condition or is taking medication that the investigator believes would interfere with his/her ability to provide informed consent, comply with the study protocol, which might confound the interpretation of the study results, or put the person at undue risk
• Subject is allergic to alcohol (alcohol pre pads are used for blood draws
• If female, subject is taking birth control medication or has long-acting reversible contraceptive
• If male, subject is undergoing hormone therapy to alter testosterone levels (injections, transdermal patch, pill, etc.)
• Subject is employed by, or has a parent, guardian, or other immediate family member employed by a company that manufactures any products that compete with any Gatorade product. If subject is unsure if a company would be considered a competitor to Gatorade, they will be asked to please let the study investigator know the name of the other company and the nature of their relationship to that company before they sign the informed consent.