Objective: To estimate the prevalence of thinness, overweight and obesity among Tibetan adolescents aged 12-17 years.

Design: Cross-sectional survey.

Setting: City of Tibet municipality, with an average altitude of more than 4000 m.

Participants: Study participants included 2642 adolescents aged 12-17 years selected from six schools using a convenient cluster sampling method.

Results: The prevalence of thinness/overweight/obesity among Tibetan adolescents was 9·4 %/5·4 %/1·4 % (China definition), 14·7 %/4·4 %/0·7 % (International Obesity Task Force (IOTF) definition), and 2·8 %/5·7 %/0·9 % (WHO definition). The prevalence of thinness and overweight was significantly different between both sexes based on each of three BMI classification criteria (P < 0·001). There was no significant difference in the prevalence of obesity between both sexes according to each of three BMI criteria. There was no clear trend in the prevalence of thinness across ages according to the China or IOTF definition (both P > 0·05), whereas an upward trend was observed for thinness in boys according to the IOTF definition (P_for trend <0·05). In contrast, the prevalence of thinness tended to decrease with increasing age in girls according to the IOTF definition and in total sample according to the WHO definition (P_for trend <0·05).

Conclusions: Among Tibetan adolescents, the prevalence of overweight and obesity is relatively low, while the prevalence of thinness is high, especially in boys. These data suggest urgent attention is needed to control adolescent thinness in Tibet.