Clinical measurements, definitions, and variables

Weight, height, waist circumference, and hip circumference were measured for each participant using standardized techniques and body mass index (BMI, kg/m²) was calculated [30]. Blood pressure was recorded as the average of two readings taken on the right arm in the sitting position with a portable OMRON BP-760 electronic blood pressure monitor (Omron Healthcare, Hoofddorp, Netherlands). Glucose tolerance was determined using an oral glucose tolerance test. After an 8-h minimum overnight fast, we measured fasting capillary blood glucose (CBG) with a One Touch Ultra glucometer (Johnson & Johnson, Milpitas, CA, USA). Oral glucose (75 g anhydrous) was administered and consumed within 5 min. Two hours later, we measured post-load CBG [31]. Blood hemoglobin (Hb) concentration was assessed using capillary blood samples and a HemoCue® HB201+ analyzer (Hemocue AB, Angelholm, SE).

Participants were categorized into BMI classes using the cut-offs for Asian populations: underweight (< 18.5 kg/m²); normal (≥18.5 kg/m² and < 23 kg/m²); overweight (≥23 kg/m² and < 25 kg/m²); obesity class I (≥ 25 kg/m² and < 30 kg/m²); and obesity class II (≥35 kg/m²) [32]. Abdominal obesity was defined as waist circumference ≥ 90 cm for men and ≥ 80 cm for women [33]. Consistent with previous studies [21, 34], participants were classified as stunted if their height was <− 2 Z-scores below the sex-specific reference population at 18 years of age, calculated as < 163.6 cm for men and < 151.8 cm for women [35]. High blood pressure was defined as mean systolic blood pressure ≥ 140 mmHg and/or mean diastolic blood pressure ≥ 90 mmHg and/or self-reported treatment with blood pressure medication [36]. As per WHO criteria, diabetes was defined as individuals with proof of previous diagnosis and/or fasting CBG ≥7 mmol/L (≥126 mg/dl) and/or a 2 h post prandial CBG value ≥12.2 mmol/L (≥220 mg/dL) [31]. Impaired glucose tolerance (IGT) was defined as a fasting CBG < 7 mmol/L and a 2-h post glucose CBG ≥8.9 mmol/L (≥160 mg/dL) but < 12.2 mmol/L (220 mg/dL) [31]. Impaired fasting glucose (IFG) was defined as a fasting CBG ≥6.1 mmol/L (≥110 mg/dL) and < 7 mmol/L (< 126 mg/dL) and a 2 h post-glucose CBG < 8.9 mmol/L (< 160 mg/dL). Pre-diabetes was defined as the existence of IGT or IFG or co-occurrence of both. Mild anemia was defined as blood Hb concentration 110–129 g/L for men and 110–119 g/L for women. Moderate and severe anemia were defined as blood Hb concentration 80–109 g/L and < 80 g/L respectively for both men and women.

Socioeconomic status (SES) was determined with an asset-based wealth index (hereafter referred to as wealth index) using a subset of 13 of 29 questions taken from the Standard of Living Index developed by the International Institute of Population Sciences (IIPS) for use in their National Family and Health Surveys (NFHS) [37]. Attributes and possessions were weighted for a maximum score of 41 using weights developed by the IIPS [38]. Higher values were therefore indicative of a greater household asset base. Caste was categorized as low caste (comprised of scheduled castes and scheduled tribes), middle caste (comprised of other backward castes and most backward castes), high caste (Brahmin caste), or not applicable (in the case of non-Hindu religion).