The relationship between obesity and hypoferraemia in adults: a systematic review.

A growing number of studies suggest a potential link between obesity and altered iron metabolism. The purpose of this systematic review was to examine existing literature on iron status in obese populations. A comprehensive literature search was conducted. Included studies recruited participants ≥ 18 years with a body mass index ≥ 30 kg m(-2) and provided descriptive statistics for haemoglobin or ferritin at a minimum. There were 25 studies meeting all eligibility criteria, of these 10 examined iron status in free-living obese individuals and 15 reported baseline iron biomarkers from bariatric surgery candidates. Non-obese comparison groups were used by 10 (40%) articles. In these, seven obese groups reported higher mean haemoglobin concentration; six reported significantly higher ferritin concentration; and four significantly lower transferrin saturation. Due to insufficient data, it was not possible to make conclusions regarding mean differences for soluble transferrin receptor (sTfR), hepcidin or C-reactive protein. Existing evidence suggests a tendency for higher haemoglobin and ferritin concentration and lower transferrin saturation in obesity. Alternation of iron biomarkers in obese populations may be a result of obesity-related inflammation and/or related comorbidities. Further research incorporating measurement of inflammatory cytokines, sTfR and hepcidin is required to confirm the impact of obesity on iron status.