Peripheral tissues (e.g. liver, adipose, muscle) express self-sustained circadian clocks that coordinate daily metabolic rhythms. The timing of clock rhythms in peripheral tissues is highly sensitive to feeding-fasting signals across the sleep-wake transition. Nutritional insults such as high fat overfeeding (HF-OF) have been shown to attenuate clock gene expression in peripheral tissues resulting in a deleterious re-programming of the circadian metabolome. Studies in humans have only superficially investigated how the circadian clock machinery is impacted by nutritional signals. The overall goal of this pilot project is to take the first steps toward developing translational methods to investigate links between changes in energy flux and the circadian system in human tissues. Using an innovative ex vivo cell culture approach the investigators will examine the impact of 3-days of HF-OF compared to eucaloric (EU) feeding on the expression of core clock genes in human subcutaneous adipose tissue (SAT). The Investigators hypothesize that compared to EU, the amplitude of clock gene expression in SAT measured over 24hrs will be attenuated following short-term HF-OF. This pilot project will serve as a launch point for designing future studies into the effects of diet and exercise on the circadian control of metabolism in adipose tissue depots as well as other tissues (e.g. muscle).

Inclusion Criteria:

• males and females aged 20-35 yr;
• BMI 25-35 kg/m2 and weight stable (±2kg in past 2mo);
• non-smoker;
• sedentary to moderately active (≤3 days of exercise per week ≤30 min of exercise per session);
• sleeping pattern of >7 hours to 9.25 hrs of sleep/night.
• subjects will be asked to identify themselves as regular consumers of 3 balanced meals per day by answering the question: "Do you eat breakfast, lunch, and dinner on ≥ 5 days per week?"

Exclusion Criteria:

• Smoker (current or within the previous 3 months);

• Use any medication that could affect lipid metabolism, insulin signaling, or sleep;

• Pregnant women will not be enrolled in the study;

• Have a job that involves shift work;

• Dwelling below Denver altitude (1,600 m) a year prior to testing;

• Travel across more than one time zone 3 wk before a study;

• chronic health conditions such as diabetes, hyper or hypothyroidism, renal or liver disease, anemia, or cancer;

• Regularly go to sleep after midnight;

  o Subjects will be excluded if they are identified as having night eating syndrome (at least 25% of food intake is consumed after the evening meal and/or at least two episodes of nocturnal eating per week);

• Allergy to lidocaine or similar compound;

• Have one or more of the following out-of-range values measured on a fasting blood sample:

  • glucose > 110 mg/dl,
  • thyroid stimulating hormone <0.5 or >5.0 µU/ml.

• Subjects who may be:

  • anemic (hemoglobin < 14.5 g/dl men, <12.3 g/dl women ),
  • have abnormal liver function tests (alanine amino transferase > 47 U/l, aspartate aminotransferase, > 47 U/l, alkaline phosphatase <39 or >117 U/l) or creatinine (>1.1 mg/dl).