Caloric restriction has beneficial metabolic effects in humans including weight loss and improvement in blood pressure and lipid levels. Intermittent fasting has emerged as a popular alternative to caloric restriction as it does not require daily adherence to a dietary protocol, but whether the benefits of fasting protocols are dependent on weight loss is not known. In this study, the investigators will explore the metabolic effects of fasting and evaluate whether these effects, including negative effects on bone metabolism, are independent of weight loss.

Inclusion Criteria:

1. Men and women, ages 21-45 years
2. BMI of at least 21 kg/m2 and up to and including BMI of 29 kg/m2
3. Normal thyroid function
4. Regular menses (women)
5. At least one first-degree relative with type 2 diabetes (T2D) and/or history of gestational diabetes

Exclusion Criteria:

1. Any chronic diseases including hypertension and Type 2 diabetes mellitus
2. Indication for lipid-lowering therapy in non-diabetics, using the more stringent AHA guideline cutoff (LDL>190 or an estimated 10-year ASCVD risk of >7.5%)
3. Chronic medications, including oral contraceptive pills
4. Pregnant and/or breastfeeding
5. History of an eating disorder
6. 25-OH vitamin D level < 20 ng/mL
7. Active substance abuse, including alcohol
8. Subjects with a prior history of intermittent fasting
9. The study physician feels that the subject may not be able to safely complete the protocol or may place themselves at risk by undergoing the protocol

Deidentified information will be shared upon request.

Beginning 12 months after publication. No end date.

Researchers who wish to access deidentified data.