The Fuel and Rhythm (FAR) Phase 2 Study

Both fuel metabolism and circadian rhythms have emerged as important targets to improve cellular and mitochondrial health and ultimately affect function in older adults. Thus, the purpose of this study is to develop minimally invasive measures that will allow us to accurately assess and detect changes in fuel metabolism and circadian rhythms in older adults following time-restricted eating.

A growing body of evidence indicates the mitochondria have an important role in the etiologies of many chronic diseases as well as the onset of physical disability in older adults. Although it is recognized that the mitochondria have an important role in many functions relevant to healthy aging, the direct assessment of mitochondrial function in humans is complicated and typically involves a muscle biopsy. Muscle tissue obtained from a biopsy can be used to provide an index of mitochondrial function, but only at a single time point. Some individuals may be discouraged from participating in research studies involving biopsies due to the perceived pain and risk involved.

Why there is a decrease in mitochondrial function with aging remains under debate, but emerging science indicates that there is a clear connection between mitochondrial biogenesis and function with fuel metabolism and circadian rhythms. Thus, the purpose of this development project is to develop relatively non-invasive measures that are sensitive to fuel metabolism and circadian health which can serve studies conducted within the University of Florida's Pepper Center in the coming years. In the proposed project, we will investigate the extent to which our measures of fuel utilization and circadian health markers are time stable and also sensitive to change following an intervention of time restricted eating, which is expected to impact these variables.

To our knowledge, no study has assessed fuel utilization patterns or circadian health markers in overweight older adults. Measurements of altered mitochondrial oxidation with a preference toward fat metabolism obtained from a blood sample would provide a sensitive biomarker that is relatively easy to obtain from participants for future interventions studies. The use of continuous glucose monitoring may also be used as surrogate measure of adherence to lifestyle interventions involving calorie restriction and/or intervention fasting, in future studies.

In addition to fuel utilization, there is growing recognition that age-related disease conditions and functional decline are associated with disruption of circadian rhythms. These observations raise the possibility that targeting circadian rhythms through timing lifestyle cues, such as meal timing, could be health promoting and may also reduce age associated declines in mobility. The ability to assess markers of circadian and metabolic health in minimally invasive ways through temperature and glucose monitoring, will provide potential valuable measures for explanatory or outcome measures in future studies.

Eligibility Criteria:
Inclusion Criteria:

* Consent to participate in the study
* Men and women ≥ 65 years old
* Self-reported difficulty walking ¼ mile or climbing a flight of stairs
* Self-reported sedentariness (\<150 minutes structured exercise per week)
* Walking speed \<1 m/sec on the 4 m walk test
* Able to walk unassisted (cane allowed)
* Have a body mass index between 25 - 40 kg/m2 (inclusive)
* HbA1c \< 5.7 %

Exclusion Criteria:

* Fasting \>12 hours per day
* Actively trying to lose weight by participating in formal weight loss program or significantly restricting calorie intake
* Resting heart rate of \>120 beats per minute, systolic blood pressure \> 180 mmHg and/or diastolic blood pressure of \> 100 mmHg
* Unstable angina, heart attack or stroke in the past 3 months
* Continuous use of supplemental oxygen to manage a chronic pulmonary condition or heart failure
* Rheumatoid arthritis, Parkinson's disease or currently on dialysis
* Active treatment for cancer in the past year
* Diabetes Mellitus
* Known history of skin sensitivity or allergic reaction to adhesives
* Taking medications that preclude fasting for 16 hours (e.g. must be taken with food at least 12 hours apart)
* Any condition that in the opinion of the investigator would impair ability to participate in the trial