This study examined the association of changes in body weight with suicide mortality in 214,105 participants, aged 18-97 years, from the MJ cohort, Taiwan. During a mean follow-up of 15.0 ± 4.9 years, 239 participants died for suicide. Mean change in body weight was 0.29 ± 1.8 Kg/year. A nonlinear dose-response relationship between changes in body weight and suicide was detected (p < 0.001), so that incidence of suicide raised when body weight decreased. The HR (95%CI) per 1 kg/year of weight loss was 1.35 (1.03-1.75) for underweight participants. These findings highlight that weight loss could be a risk factor for suicide, especially among underweight people.