I cringe when someone tells a dancer to lose weight "to stay healthy" or "for your joints' health". Because that's so misleading. In dance, injury and body weight are not associated. Yet so many people will blame weight to be the cause of an injury or joint pain. 

Factors that increase the risk of injuries:

• Range of motion (both too much and lack of)

• Physical anomalies (e.g. scoliosis)

• Subuptimal nutrition

• Disordered eating behaviours

• Late menarche

Knee injuries, for example, which commonly increase around the pubertal age, are due to poor balance and landing techniques and weakness of the muscles, especially of the medial knee. 

Dieting impose restrictive eating practices and food and weight pre-occupation. When you lose weight in the initial stages that is because you're not giving yourself enough energy to sustain your body's needs, leading to a degree of malnutrition.So with dieting you end up with Suboptiomal Nutrition and Disordered Eating Behaviours.That's two out of the five injury-promoting factors. Many would go on a diet to "cut down body fat".But too little body fat will delay the onset of menarche, on top of all other health consequence.So dieting can conform the delay of menarche, if anything. So that's now THREE out of the FIVE injury-promoting factors.  ... This doesn't sound safe to me.   

Dieting does not protect you against joint injuries

Dieting actually promotes injuries.  

So if someone tells you to lose weight "for your joints" or "for your health" (and preventing injuries is one of the most important health factors for dancers), you know what to do. Stand up and say No. Because by saying No, you are saying "As a responsible dancer, I am going to give myself enough fuel to build a strong body that will help prevent injuries, because it's important for me to be able to dance at my best".   

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Thomas JJ. Keel PK. Heatherton TF. Disordered eating and injuries among adolescent ballet dancers. Eat Weight Disord. 2011. Sep, 16(3):e216-22.

Ekegren CL. Quested R. Brodrick A. Injuries in pre-professional ballet dancers: Incidence, characteristics and consequences. J Sci Med Sport. 2014. May;17(3):271-5.

Steinberg N, Siev-Ner I, Peleg S, Dar G, Masharawi Y, Zee A and Hershkovitz I. Extrinsic and intrinsic risk factors associated with injuries in young dancers aged 8-16 years. J Sports Sci. 2012;30(5):485-95.

Karapanou O. Papadimitriou A. Determinants of menarche. Reprod Biol Endocrinol. 2010;8:115-22