The study evaluated the impact of the Lancet Commission definition of obesity, which requires, in addition to a BMI ≥ 25.0 kg/m², an additional anthropometric measurement to confirm excess adiposity, on its prevalence in East Asian Chinese in two community-based cohorts. The prevalence of obesity according to the Asian cut-off of BMI ≥ 25.0 kg/m² was 44.5% in men and 26.7% in women in the cross-sectional cohort, but fell to 33.8% in men and 24.1% in women according to the Lancet criteria. These criteria reclassified a proportion of individuals with BMI ≥ 25.0 kg/m² but normal waist circumference as non-obese (category iii), who had an adverse cardiometabolic profile with higher insulin resistance and visceral adiposity among the five categories. In a long-term cohort with a follow-up of more than 20 years, subjects with clinical obesity had the worst cardiovascular-renal-metabolic outcomes, including all-cause mortality. The reclassified non-obese (category iii) showed an intermediate risk of adverse outcomes between preclinical obesity and overweight. The main limitation is that the participants were exclusively Chinese, so the findings may not apply to other ethnic groups.