Cerebral blood flow (CBF) is essential for maintaining brain health and function, as it ensures delivery oxygen and nutrients necessary to support neuronal activity. Reduced CBF can impair the brain's ability to meet its metabolic demands, leading to deficits in cognitive ability. Impairments in CBF are associated with cognitive decline and neurodegenerative disease such as Alzheimer's and dementia. Many factors influence CBF, but recently lactate has emerged as a key player. Blood glucose has long been considered the primary fuel for the brain, but emerging evidence indicates that lactate may be the preferred fuel for neurons, and lactate may become even more important under stressful conditions.

Individuals with obesity often have impaired lactate metabolism resulting in higher resting blood lactate concentrations and reduced ability to clear lactate after a physiological stress. At the same time, it is known that exercise is a powerful intervention for improving lactate metabolism.

Thus, this project seeks to investigate the role of lactate in brain blood flow in individuals with and without obesity as well as establish if short term exercise training (individuals with obesity only) will alter circulating lactate concentrations at rest and in response to exercise.

Blood lactate is often considered a waste product from aerobic metabolism. Many people assume it causes fatigue and muscle. Lactate is a signaling molecule in the body. In addition lactate is also a fuel. Evidence supports that lactate may be more important when the brain is stressed. We also know that individuals with obesity and/or type 2 diabetes may have impaired lactate metabolism.

The investigators will compare brain blood flow and lactate response to an exercise stress test and submaximal exercise in obese and non-obese individuals.

Inclusion Criteria:

healthy adult men and women 18-45 years of age BMI 18-40 kg/m2 not pregnant, premenopausal with regular menstrual cycles not breastfeeding non-nicotine users

Exclusion Criteria:

medications known to affect sleep, autonomic control, blood lactate levels or metabolic, or cardiovascular function (PI discretion) self-reported history of hepatic, renal, pulmonary, cardiovascular, or neurological disease, stroke or neurovascular disease, bleeding/clotting disorders, sleep apnea or other sleep disorders, diabetes, history of alcoholism or substance abuse major cardiovascular event or surgical procedure within the past three months hypertension (>140/90 mmHg or at PIs discretion).

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Individuals that live in the area of Columbia, MO

only coded IPD will be shared that is used in the results published

Beginning 1 year after publication and ending 5 yr after publication of results

Mean data will be shared for meta analysis For access to individual data, a proposal that described the planned analysis must be submitted and an agree must be signed by the applicant. These documents would be submitted to the PI.