In 2017, Hussain et al. reported evidence of the metabolic roots of back pain, which is probably relevant to other kinds of chronic pain as well.
The majority (82%) of 5000 Australians reported back pain on a questionnaire, and in 27% of them it was bad enough to be disabling. When compared to their fat mass fat distribution — a well-known indicator of metabolic disorders — a clear pattern emerged: back pain intensity and disability go up with measures of fat mass and distribution.
This data challenges that idea that weight is a “mechanical” problem for backs — greater weight causing greater stress on spinal joints — which is an extremely popular assumption. Nearly universal, actually. You’d be hard-pressed to find someone who does not think that extra weight is a physical risk factor for back pain.
What this evidence does suggest is that “systemic metabolic factors associated with adiposity play a major role in the pathogenesis of LBP.” The weight isn’t the problem, but the biochemistry of being out of shape.
This is a particularly fine example of what I mean when I argue that we need to look beyond trivial physical stresses and biomechanical factors to the messy “wet” factors in chronic pain, the things that make us more vulnerable to pain.