**Background:** Metabolic syndrome (MetS) is a cluster of metabolic abnormalities including central obesity, elevated blood pressure, elevated triglycerides, low HDL-C, and impaired fasting glucose, affecting approximately 25% of the global population. In China, the pooled prevalence of MetS is 24.5%, but it varies greatly among ethnic groups, with a reported prevalence of 6.17% among Tibetans. However, recent studies show that Tibetans transitioning from nomadic to urban areas have MetS prevalence similar to the national rate (30.1% in men, 32.1% in women). Diet is an important modifiable risk factor, and while cross-sectional studies have examined dietary patterns (DPs) and MetS in Tibetans, no cohort study had been conducted. Additionally, high altitude may influence metabolic diseases through oxidative stress, but the interaction between diet and altitude had not been explored.
**Methods:** This community-based open cohort study included 1832 Tibetan adults from two communities in the Golmud suburbs (2800 m above sea level) who had settled or semi-settled from pure pastoral areas (>4000 m). Data were collected in two waves (2018 and 2022). Dietary intake was assessed using a revised food frequency questionnaire (FFQ) with 27 food groups. Three DPs were identified using factor analysis (principal-component factors with varimax rotation): modern DP (pulses, whole grains, fresh fruit, nuts, meat, processed foods), urban DP (refined grains, beef/mutton, eggs, vegetables), and pastoral DP (Tibetan cheese, tsamba, butter/milk tea, whole-fat dairy, desserts). Mixed-effect logistic regression was used to evaluate associations between DP tertiles and MetS and its components, adjusting for sociodemographic factors, lifestyle factors, and altitude. Interaction analyses examined modification effects of altitude.
**Key Results:** The prevalence of MetS was 30.1% (men 32.3%, women 28.3%). The urban DP significantly increased MetS risk: adjusted ORs (95% CI) for T2 and T3 vs. T1 were 1.20 (0.79, 1.83) and 2.25 (1.36, 3.73), respectively (p trend=0.002). The modern DP increased risk of elevated BP (OR 2.07, 95% CI 1.27-3.39 for T3 vs. T1, p trend=0.002) and elevated TAG (OR 1.50, 95% CI 1.00-2.26 for T3 vs. T1, p trend=0.033), but decreased risk of low HDL-C (OR 0.58, 95% CI 0.47-0.72 for T3 vs. T1, p trend<0.001). The pastoral DP was protective against central obesity (OR 0.57, 95% CI 0.35-0.92 for T3 vs. T1, p trend=0.019) and elevated BP (OR 0.64, 95% CI 0.43-0.96 for T3 vs. T1, p trend=0.030), but increased risk of impaired FBG after altitude adjustment (OR 1.42, 95% CI 1.06-1.90 for T3 vs. T1, p trend=0.015). Significant interactions were found between altitude and modern DP for elevated BP (p interaction=0.028) and between altitude and pastoral DP for low HDL-C (p interaction=0.002). At high altitude (2800 m), pastoral DP was protective for low HDL-C (OR 0.62, 95% CI 0.41-0.94 for T3), but at very high altitude (>4000 m), it became a risk factor (OR 3.94, 95% CI 1.36-11.41 for T3).
**Clinical Implications:** This first cohort study of Tibetan adults demonstrates that urbanization-related dietary changes increase MetS risk, while traditional pastoral diet offers some protection but may be harmful at very high altitudes. The findings highlight the need for culturally adapted dietary interventions for Tibetan populations undergoing nutritional transition. The altitude modification effect suggests that dietary recommendations may need to account for altitude exposure. Public health strategies under the Healthy China 2030 initiative should consider these population-specific findings to reduce MetS burden in Tibetan communities.