There is very little literature about the use of MUAC for adolescents. It has been deemed a good measure of undernutrition in pregenant women -including pregnant adolescents. 

A 2010 study of adolescents in India compared MUAC to BMI (adult cut-offs, unfortunately) - they conclude that MUAC was 94.6% sensitive and 71.2% specific at detecting malnutrition in adolescents compared to BMI. They conclude that: mid arm circumference measurement is a reliable and a feasible method of assessment of nutritional status of adolescents. However, the researchers feel that there are some aspects of MUAC that should be kept in mind. MUAC changes substantially with age during adolescence. As a result, a different cut-off point must be used for adolescents of different ages. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2940185/

A 2013 systematic review of the literature on MUAC for adolescents and adults found only one study using MUAC for adolescents, which showed an association between significantly lower mean hemoglobin levels (anemia) in those with low MUAC (<22 cm) than those with MUAC ≥22 cm. For other adults, the review concludes: "1) in non-pregnant adults, low MUAC may be a good substitute for BMI <18.5, and 2) in pregnant women, low MUAC at any time during pregnancy is associated with higher risk of having an infant with LBW. While most of these studies chose cutoffs of 22–24 cm and found significant associations with the outcomes, none of the studies adequately explored the optimal MUAC cutoffs associated with these outcomes" http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.652.8324