To examine benefits of a probiotic for youth with chronic pain and a Body Mass Index >=85th percentile.

The purpose of the current study: (1) examine whether a 7-11 week supplement of a single-strain probiotic (Lactobascillus Plantarum, Lp299v) reduces systemic inflammation; (2) determine whether reductions in systemic inflammation will correlate with reductions in pain, disability, mood impairment and changes in mechanical pain threshold and mechanical pain sensitization; (3) Explore whether reductions in systemic inflammation will correlate with reductions in other outcomes.

Inclusion Criteria:

1. Male or female biological sex
2. 13-17 years of age
3. Body Mass Index ≥85th percentile for sex and age

Exclusion Criteria:

1. Probiotic (or prebiotic) supplement use or antibiotic use within the past month
2. Chronic inflammatory or autoimmune disease with the exception of well-controlled hypothyroidism or intermittent or mild persistent asthma not requiring the use of daily inhaled steroids
3. Patients who have had a poor response to blood draw or immunizations in the past
4. Chronic use of medications known to alter gastrointestinal function or inflammation (e.g. metformin, non-steroidal anti-inflammatory medications)
5. Any condition that, in the investigator's opinion, may compromise study participation or may confound the interpretation of the study results
6. Use of illicit drugs
7. Females who are pregnant or lactating