The investigators are enrolling both Normal-Weight Healthy (NWH) and Obesity-Prediabetes (OPD) research participants. At this time (5/2023) the investigators are focusing on the NWH group.
Inclusion Criteria:
* For the Normal-Weight Healthy (NWH) cohort: Healthy male and female adults, age 18-50, with BMI 18-24.9 kg/m2 inclusively
* For the Obesity-Prediabetes (OPD) cohort: Male and female adults, age 18-50, with BMI ≥30 kg/m2 and prediabetes
* All participants must be able to understand study procedures, to comply with the procedures for the entire length of the study and be fully mobile.
Exclusion Criteria:
* Sleep disorder including insomnia, untreated moderate-severe sleep apnea, restless leg syndrome, or narcolepsy
* Night shift work
* Extreme delayed sleep phase defined as self-reported routine bedtime later than 1:00 AM or having mid-sleep on free days later than 5:00 AM on the Munich Chronotype Questionnaire (MCTQ) or DLMO later than 24:00
* Gastroesophageal reflux disease that affects ability to tolerate a dinner close to bedtime
* Active smoking
* Current drug or alcohol use or dependence that, in the opinion of the site investigator, would interfere with adherence to study requirements.
* Diabetes (type 1 or 2) or on any diabetes medications besides metformin
* Evidence of metabolic or cardiovascular disease, or disease that may influence metabolism (e.g. cancer, thyroid disease)
* Hemoglobin A1c ≥5.7% for NWH cohort; Hemoglobin A1c ≥6.5% for OPD cohort
* Hemoglobin \< 10 g/dL
* Self-reported kidney disease
* Any known history of an inherited metabolic disorder
* Pregnant or lactating female (pregnancy test will be required prior to metabolic visits)
* Peri-menopausal or post-menopausal female as determined by follicle stimulating hormone of \> 30 mIU/mL or fewer than 3 menstrual periods in 6 months
* Professional or collegiate athlete
* Participants who have travelled across time zones must have adequate time to recover from jet lag prior to enrollment (i.e., at least 3 days per time zone). Travel across \>1 time zone after enrollment in the study will not be permitted.
* Weight less than 40 kg or more than 180 kg
* Gastrointestinal disorders that can lead to obstruction of the digestive tract (i.e. diverticular disease, history of bowel obstruction, inflammatory bowel disease, motility disorder)
* History of any surgical procedures in the gastrointestinal tract.
* Swallowing disorders
* Taking any prescription medication or other drug that may influence metabolism (e.g. diet/weight-loss medication, asthma medication, blood pressure medication, psychiatric medications, corticosteroids, or other medications at the discretion of the PI and/or study team)
* Chronic use of sedative hypnotics, anxiolytics, opiates
* Use of medications that can affect circadian rhythm (beta blockers, melatonin)
* Presence of a cardiac pacemaker or other implanted electro-medical devices
* Those who have to undergo strong electromagnetic field during the period of use of the ingestible thermosensor (i.e. MRI)
* Weight loss or gain of ≥ 5% of total body weight over the preceding 3 months
* Currently participating in a weight loss program
* Prior bariatric surgery
* Volunteers with strict dietary concerns (e.g. vegetarian or kosher diet, food allergies)
* History of significant intravenous access issues
* Non-English speaking individuals: The complexity of the instructions for various components of the study would make the study procedures difficult to follow in the setting of a language barrier.
* Other conditions or situations at the discretion of the PI
