This study aims to evaluate the effects of oral glycine supplementation on plasma glycine concentration, intracellular glutathione (GSH) concentration, plasma acylglycine concentration, urine acylglycine concentration, and insulin resistance in subjects with morbid obesity.

This is an open-labelled trial. 20 adults with morbid obesity will be recruited. Following screening and baseline metabolic evaluations, eligible subjects will be given oral glycine supplements for 14 ± 5 days. Upon completing glycine supplementation, subjects will return for their post-supplement metabolic assessment.

The investigators hypothesize that oral glycine supplementation in morbidly obese patients normalizes plasma glycine concentration, increases intracellular GSH concentration, increases plasma and urinary acylglycine concentration, and improves insulin resistance.

Inclusion Criteria:

1. Age: 21-65 years
2. BMI ≥ 32.5 kg/m2
3. Able to provide informed consent
4. Able to maintain present diet throughout the study duration

Exclusion Criteria:

1. Weight > 150 kg
2. Type 2 Diabetes Mellitus
3. Allergy to soy
4. Ongoing treatment with weight-loss medications (e.g. orlistat, phentermine, liraglutide)
5. Systemic steroid usage (eg. prednisolone, hydrocortisone, cortisone, dexamethasone)
6. Renal impairment (estimated creatinine clearance estimated by Cockcroft-Gault Equation < 60 ml/min)
7. Haemoglobin concentration < 10 g/L
8. Serum alanine aminotransferase or aspartate aminotransferase above 2x upper limit of normal
9. Uncontrolled hypertension (BP > 180/110 mmHg)
10. Pregnancy
11. Nursing mothers
12. Uncontrolled thyroid disease
13. Surgery requiring general anaesthesia within 4-weeks before enrolment
14. Psychiatric disorders requiring medication
15. Significant alcohol intake (> 1 unit per day for women and > 2 units per day for men)
16. Cancer within the last 3-years (except squamous cell and basal cell cancer of the skin)
17. Any factors likely to limit adherence to study protocol