The goal if this study is to determine how oral lactate ingestion affects markers of appetite regulation. Researchers will compare oral lactate ingestion to a sodium chloride placebo. Participants will consume the lactate or placebo solution and then have blood samples and assessments of appetite over the course of 90 min. Free-living energy intake will be measured for 3 days surrounding each experimental session.

The purpose of this study is to explore the effects of oral lactate ingestion on appetite regulation in humans. To do this males and females will report to the laboratory for 2 experimental sessions completed in a counterbalanced, double-blinded manner. During one session a lactate solution will be ingested, in another session an equimolar sodium chloride solution will be ingested that matches the osmolarity of the lactate condition. Venous blood samples and subjective appetite perceptions will be obtained at five time points during each experimental session. Energy expenditure will be measured through accelerometers placed on the participants anterior thigh by an investigator on the morning the day before the session and worn over the experimental period (day before, day of, day after) recording their physical activity. Energy intake will be tracked using a smartphone mobile application called Keenoa over the same time period the accelerometers are worn.

Inclusion Criteria:

• Deemed healthy using Canadian Society for Exercise Physiology Get Active Questionnaire
• Female participants must be eumenorrheic (menstrual cycle length between 21-35 days)

Exclusion Criteria:

• Failure to meet inclusion criteria
• Taking supplements or medications known to affect metabolism (e.g., creatine, beta-blockers)
• Currently pregnant or a pregnancy of >3 months within the last 3 years,

The allocation of lactate and placebo will be completed by a researcher not involved in data collection. Both the participant and the researchers collecting and analyzing the data will be blinded to the treatment allocation. This will be completed in a counter-balanced order.