The purpose of this research study is to investigate how body weight and weight-loss surgery affect the natural chemicals found in scalp hair over time. We will also find out how common and severe hair thinning/hair loss and muscle loss are in the first 6 months after bariatric surgery.

The investigators will recruit 30 subjects with severe obesity scheduled for bariatric surgery and 30 healthy-weight controls.

Following written informed consent, the investigators will collect the study subject's medical information, conduct a dietary and quality-of-life survey, take body measurements, obtain scalp photos, perform a hair-pull test, collect a hair sample, and conduct muscle strength testing. Controls will be assessed only at baseline. Those with severe obesity will return at 4 ± 2 weeks, 12 ± 4 weeks, and 26 ± 4 weeks following bariatric surgery to repeat the study procedures.

Inclusion Criteria:

All subjects:

1. Age 21-70 years
2. Ability to provide informed consent

Healthy weight controls:

1. BMI of 18.5-24.9 kg/m2
2. No chronic disease
3. No long-term medications

Severe obesity:

1. BMI of > 32.5 kg/m2
2. Scheduled to undergo bariatric surgery

Exclusion Criteria:

1. Pregnancy
2. Any factors likely to limit adherence to study protocol
3. Any history of autoimmune or scarring alopecia (eg. alopecia areata, discoid lupus, lichen planopilaris)

Subjects with severe obesity will be recruited from the Singapore General Hospital's obesity clinic, while controls will be healthy volunteers.

All IPD that underlie results in a publication