China faces significant challenges from non-communicable diseases (NCDs) due to increasing urbanization and westernization. Understanding the roles of nutrition, lifestyle, and genetic susceptibility in NCD development among the Chinese population is crucial for public health. Unhealthy diets and lifestyles are known to contribute significantly to NCDs. However, Asians, compared to Western populations, may have a greater genetic predisposition to diseases like type 2 diabetes (T2DM). These ethnic differences in risk factor associations with NCDs might stem from variations in genetic susceptibility or interactions between diet, lifestyle, and genetic background. The scarcity of epidemiological studies examining environmental and genetic factors and their interplay in NCD risk in China motivated the initiation of the Nutrition and Health in Southwest China (NHSC) study. The NHSC study aims to investigate the impact of diet, lifestyle, genetic background, and their interactions on obesity, diabetes, hypertension, cardiovascular diseases, and other NCDs among Chinese adults, filling a critical gap in existing research.

The introduction cites several studies highlighting the increasing burden of NCDs in China due to urbanization and westernization [1, 2], the significant role of unhealthy diet and lifestyle in NCD development [3], and the potential for greater genetic predisposition to T2DM in Asians compared to Western populations [4, 5]. The lack of comprehensive epidemiological studies in China investigating the combined effects of environmental and genetic factors on NCD risk is emphasized, underscoring the rationale for the NHSC study.

The NHSC study is a prospective cohort study initiated in 2013, employing a stratified sampling design across urban and rural areas in Southwest China. A two-stage (household-person) sampling method was used, selecting 150 households randomly from each of 54 study sites. Eligible participants were adults aged 18–70 who had lived in their current residence for at least a year. Replacement households were recruited to maintain adequate sample size and representativeness. Baseline data collection concluded in December 2018, with planned 2-year follow-ups. Data collection includes questionnaires, anthropometric measurements, medical examinations, and biochemical measurements. Dietary intake was assessed using three 24-hour recalls and a food frequency questionnaire (FFQ). Eating behaviors, physical activity levels (including sedentary behaviors), smoking habits, sleep quality, and work/life stress were also assessed using questionnaires. Anthropometric measurements (height, weight, waist and hip circumferences, skinfold thicknesses) were performed by trained investigators. Blood pressure was measured twice using a mercury sphygmomanometer. Blood samples were collected for biochemical analysis (glucose metabolism markers, lipids, serum calcium, telomere length, inflammatory markers). Genomic DNA was extracted from blood samples for genotyping using Illumina's Infinium II technology (Human HAP300 panel). Sociodemographic data (age, residence, marital status, income, education, employment) and family history of chronic diseases were also collected. Rigorous quality assurance procedures, including standardized protocols and training, were implemented. The study was approved by the Ethics Committee of Sichuan University, and all participants provided written informed consent.

A total of 7926 adults completed the baseline questionnaire. The average age was 42.6 years, with slightly more than half being female. Analyses of baseline data revealed associations between higher dietary energy density and increased BMI, fat mass index, fat-free mass index, and percentage body fat. Higher dietary glycemic index, glycemic load, or serum 25(OH)D levels were associated with less favorable glucose homeostasis. Reduced television viewing time and adherence to a healthy eating pattern appeared to be positively associated with cellular aging measures. Table 2 provides a detailed summary of participants' characteristics, including nutritional data, lifestyle data, anthropometry, and biochemical measurements.

The NHSC study's findings provide valuable insights into the relationship between dietary patterns, lifestyle factors, and health outcomes in a large sample of Southwestern Chinese adults. The observed associations between dietary energy density and various body composition parameters highlight the importance of energy balance in weight management. The relationships between dietary glycemic index/load and glucose homeostasis underscore the role of carbohydrate quality in metabolic health. The study suggests that lifestyle interventions targeting television viewing and promoting healthy eating could positively impact cellular aging processes. The prospective nature of the study will allow for the examination of long-term health outcomes and the identification of potential risk factors for NCDs. The large sample size and comprehensive data collection enhance the generalizability and power of the findings.

The NHSC cohort offers a rich dataset for investigating the complex interplay between genetics, nutrition, lifestyle, and NCD risk in Southwestern Chinese adults. The study's findings underscore the importance of considering dietary quality, lifestyle factors, and potentially genetic predispositions when designing interventions aimed at preventing NCDs in this population. Future research should focus on exploring the identified associations in more depth, investigating gene-environment interactions, and assessing the long-term effects of these factors on NCD incidence and progression.

While the NHSC study is large and comprehensive, some limitations should be considered. Self-reported data on diet, lifestyle, and health behaviors are subject to recall bias and potential inaccuracies. The generalizability of findings may be limited to the Southwestern Chinese population studied. Further research is needed to confirm the findings and explore potential causal relationships.