Chronic low back pain (CLBP) is a global health problem. The first step for developing effective treatments is a better understanding of underlying mechanisms, including its comorbidities. Cumulative findings, including breakthrough findings from our own group, point to impaired glucose metabolism as an important CLBP comorbidity. In addition to its metabolic role, the insulin-like growth factor 1 (IGF1)/ growth hormone (GH) axis plays a key role in pain modulation. Therefore, the project aims to examine whether DNA methylation and functional protein levels predicts postprandial glycemic responses to standardized drinks, standardized meals, and real-life meals in patients with CLBP. This will be examined using two (i.e., 1 in CLBP and 1 in healthy controls) double-blind, randomized cross-over experiments (high versus low glycaemic index beverages). After the 14-day experimental phase, all participants will be studied for an additional week to examine whether the experimental findings have ecological validity, i.e., whether they can be confirmed in response to real-life meals in their home environment. Genome-wide changes in DNA methylation will be studied using whole genome bisulfite sequencing and targeted next-generation sequencing. The project allows identification of a biomarker for a potentially very significant CLBP comorbidity, including identifying targetable mechanisms to develop innovative, personalized treatments.