In Western countries the increasing prevalence of obesity in young people is a major public health concern. While the focus has been on reducing obesity, paradoxically the success of these campaigns may result in unhealthy nutritional practices. The aim of this study was to investigate the use and impact of weight control techniques on the health of adolescent females. Using Analysis of Variance we compared physiological and biochemical markers of health against responses to a modified, Schools Physical Activity and Nutrition Survey (SPANS) in 482 adolescent females (14-17 yrs) from secondary schools in the northern Sydney and Central Coast regions of New South Wales, Australia. Participants who 'often' used weight control methods had, on average, a healthy BMI of 22.5 (SD=3.7). However, comparison of blood derived markers between participants who 'never', 'occasionally' or 'often' used weight reduction techniques showed that, those who 'often' used weight control methods had significantly lower haemoglobin (p<0.05), alkaline phosphatase (p<0.001), bilirubin (p<0.05), albumin (p<0.05), total protein (p<0.05), and calcium (p<0.05), but higher blood levels of creatinine (p<0.05) and potassium (p<0.05). These data suggest that the use of common weight control techniques by healthy weight adolescent females can produce a metabolically divergent group whose biochemical markers are consistent with subtle levels of chronic under-nutrition.