Association between adiposity and iron status in women of reproductive age: data from the UK National Diet and Nutrition Survey 2008-2019 (NDNS): Data from the UK National Diet and Nutrition Survey (NDNS) 2008–2019

BACKGROUND: Overweight/obesity and iron deficiency are highly prevalent in women of reproductive age (WRA), impacting on women's health. Obesity is a risk factor for nutritional deficiencies but its association with iron deficiency is unclear.

OBJECTIVE: To determine the association between adiposity and markers of iron status and iron deficiency prevalence in WRA.

METHODS: This cross-sectional study analyzed the National Diet and Nutrition Survey (NDNS, 2008-2019) data, focusing on women aged 18-49y with BMI ≥18.5 kg/m 2. Prevalence of anemia, Iron Deficiency Anemia (IDA), and Iron Deficiency (ID) were analyzed. Ferritin was adjusted for C-reactive protein. Iron status was assessed across high and low BMI, waist circumference (WC), waist-to-height (WHtR), and waist-to-hip ratio (WHR). Chi 2, linear and logistic regression were performed adjusting for covariates.

RESULTS: Among 1,098 WRA, 496 normal weight and 602 overweight/obesity, prevalence rates were: anemia 9.2% and IDA 6.8%. Anemia was more prevalent in those with higher WHtR and WHR (11.9% vs 5.9% and 16.7% vs 6.5%, both p<0.001). WRA with increased WC, WHtR, and WHR had higher IDA prevalence than those with lower adiposity. (8.5% vs 4.3%, p=0.005; 9.4% vs 3.3%, p<0.001; 12.1% vs 4.9%, p<0.001). ID prevalence was 49.7% (ferritin cut-off 30 μg/L) and 19.6% (ferritin cut-off 15 μg/L), showing similar rates across adiposity groups. ID prevalence defined by soluble transferrin receptor (sTfR) was higher in women with increased WHR (p=0.001). Higher WHR predicted ID categorized by sTfR (aOR 2.104, p=0.004), and WHtR and WHR predicted anemia and IDA (anemia: WHtR aOR 2.006 p=0.036; WHR aOR 4.489 p<0.001; IDA: WHtR: aOR 2.942, p=0.012; WHR aOR 4.142, p<0.001).

CONCLUSIONS: At least one in five WRA in the UK are iron deficient, highlighting the need to revise current policies. Greater central adiposity was strongly associated with impaired iron status and the development of anemia, IDA, and ID.