Our study is based on a large collective of 269 patients with AN, the vast majority of whom experienced a favourable long-term outcome, eventually achieving a stable BMI within normal range and adequate psychosocial functioning. Detailed body measurements were available from 230 patients.
The increase of BMI to at least low-normal values is the therapeutic aim of refeeding in AN. In general, this implicates a regain of the lost body fat, which is a highly relevant prognostic criterion: Failure to achieve a normal body composition is a risk factor for relapse [2, 8]. Attempts have been made to exactly monitor the increase of body fat. For this purpose, skinfold anthropometry and DXA as well as whole-body impedance vector components, resistance (R) and reactance (X(c) have been used [3–6].
Apart from these more or less sophisticated methods simple measurement of the circumference at different regions of the body have been applied as a comparatively crude additional monitoring of regional weight gain or weight loss, respectively [2, 5]. Kerruish in 2002 found significant correlations between triceps skinfold thickness and percentage of body fat as measured by DXA and BMI and percentage of body fat likewise determined by DXA in adolescent AN patients.
There are numerous publications about the distribution of subcutaneous fat tissue in AN prior to and after short-term or long-term complete or partial weight restoration. The studies were carried out in small collectives of patients and controls the number of which ranged between 15 and 64 individuals.
The findings concerning the pretherapeutic distribution of fat were in part contradictory concerning the distribution at the trunk or the extremities if compared to healthy controls. Some authors described predominant fat loss at the extremities [9, 10], others found predominant loss at the trunk [1] especially in adolescent girls, whereas a few studies described a general loss of fat tissue without predilection of special regions [11–13]. There was, however, unanimity about the fact, that the gain of fat tissue at the trunk was predominant during short term weight restoration, and that this effect levelled out during the further course of weight gain and weight consolidation [3, 9, 14].
Our pretreatment body measurements showed that adults had higher measurement values than adolescents at the time of admission. The difference, in general, was more pronounced at the trunk than at the extremities. This corroborates the findings of El Ghoch and De Alvaro [1, 3, 9, 13]. We were also able to confirm the findings of El Ghoch [3, 9, 13], that the highest absolute gain in circumference after initial refeeding was at the trunk. However, if the gain was expressed as percent of the value at admission, the highest value was for circumference of thigh, followed by upper waist, lower waist, upper arm and knee. These findings may explain the somewhat contradictory results in the literature.
Thigh circumference seems to constitute a special parameter. In 2011 Konstantynovich compared body measurements of 64 adolescent and adult females with 71 healthy controls. He found that thigh circumference was the most specific and sensitive anthropometric marker of body fat. It correlated with DXA-FM and BMI, demonstrating even a slight clinical advantage over BMI in his cohort. He suggested that this simple measurement might also serve as a useful predictor of body fatness in adolescent girls with AN [5].
In the present, large collective we were able to confirm the findings of Konstantynovic [<link rid="bib5">5</link>]. We found that out of all 13 measurement points the thigh circumference showed the best correlation to BMI. What is more, a circumference greater than 50 cm was strongly related to a BMI of at least 18. This effect was independent of age, height or sex of the patient. Interestingly, a thigh circumference greater than 50 if achieved after the first refeeding cycle was also a highly significant predictor of a favourable long-term course. BMI > = 18 after the first treatment cycle, in contrast, had no prognostic impact.