Inclusion Criteria:

1. Subjects ≥18 and ≤45 years of age

2. Lean women with PCOS (BMI: ≤ 25 kg/m2)

3. Signed informed consent

4. Exclusion of late-onset adrenal hyperplasia by a fasting serum 17- hydroxy
progesterone concentration below 200 ng/dl.

5. Acceptable health based on interview, medical history, physical examination, and
laboratory tests (SMA20 and CBC).

6. Not dieting and no change in body weight >10 lb = 4.5 kg within the last 6 months

7. Stable physical activity pattern during the three months immediately preceding study
initiation

8. Hyperandrogenemia (elevated free testosterone).

9. Normal liver and kidney function

10. Fasting blood glucose <110 mg/dl.

11. No metabolic disease

12. Usually wakes up between 05:00 and 07:00 and goes to sleep between 22:00 and 24:00.

13. Normal TSH and FT4 levels and serum prolactin

14. Acceptable health based on interview, medical history, physical examination, and
laboratory tests

Exclusion Criteria:

1. Diabetes mellitus diagnosed by fasting glucose or a 2-hour OGTT, or fasting glucose
> 110 mg/dl

2. Clinically significant pulmonary, cardiac, renal, hepatic, neurologic, psychiatric,
infectious, malignant disease (other than skin cancer).

3. Current use of oral contraceptives

4. Serum creatinine level > 1.5 mg/dl

5. Abnormal liver function tests defined as an increase by a factor of at least 2 above
the upper normal limit of alanine aminotransferase and/or aspartate

6. Any physiologic or mechanical problems preventing dietary adherence

7. Pregnant or lactating

8. Participating in another dietary program or use of weight-loss medications

9. Documented or suspected history (within one year) of illicit drug abuse or
alcoholism.

10. Use of psychotropic or anoretic medication during the month immediately prior to
study onset

11. Night or rotating shift work

12. Jet lag during the 2 week period immediately prior to study onset

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