Strength Training and Eating Disorders (STERK - Styrketrening og Spiseforstyrrelser)

ED are mental disorders which often lead to serious medical complications such as hormone disturbances, osteopenia/osteoporosis, and myopathy. More than 90% of females with anorexia nervosa (AN) have osteopenia, and almost 40% have osteoporosis. Osteoporosis in the European Union is estimated to cost 37 billion euros each year, and the majority of persons with osteoporosis are untreated. Although economic analysis of osteoporosis in Norway is lacking, the prevalence of osteoporosis in Norway is among the world's highest.

Strength training is effective in treatment of osteoporosis among postmenopausal women. Despite this, evidence based knowledge about strength training as a possible treatment-option for osteopenia/osteoporosis in ED is lacking. Due to the long half-life of bisphosphonates, such medications must be used carefully among young adults. Hence, there are no current well-documented treatment strategies for osteopenia/osteoporosis for this age group.

Although excessive physical activity is a common symptom among persons with ED, strength training is an exercise modality rarely used in this population. In addition, restoration of body weight is an important treatment goal for underweight persons with ED. Such a weight restoration leads to altered body composition with higher increase in adipose tissue compared to lean tissue, and the adipose tissue often redistribute to more abdominal fat. Such altered body composition might increase risk of cardiovascular disease and increased body dissatisfaction, and hence increase risk of relapse.

Strength training affects body composition in persons both with and without ED. It is therefore interesting to examine if strength training intervention affects body dissatisfaction, and hence reduce psychopathology and increase quality of life, among persons suffering from ED.

Existing studies with strength training intervention use different repetitions, sets and intensities. Campos et al. found that few repetitions (i.e. 3-5 rep x 3 sets) were more effective in increasing muscle strength compared to medium (9-11 rep x 3) and many repetitions (20-28 rep x 2), while the latter gave largest increase in muscular endurance among healthy males. Mosti et al. found increased bone mass in lumbar spine and femur neck and alterations in blood bone markers after 12 weeks of strength training (3-5 reps x 4 sets, 85-90% of 1RM) among postmenopausal women with osteopenia/osteoporosis. A study using both low and high intensity strength training intervention lasting for 12 months found increased bone mineral density (BMD) in lumbar spine among healthy elderly women. The few existing studies using strength training among persons with ED have all used low intensity strength training, and none of these have examined the effects on bone health. Two randomized controlled trials found effect of strength training on body composition, muscle strength and quality of life among persons with Anorexia Nervosa, whereas Del Valle et al. only found effects on quality of life. The low intensity might explain the lack of effects in the latter study. It is therefore a need for studies using adequate dosage of strength training among persons with ED.