Directly measured free 25-hydroxy vitamin D levels show no evidence of vitamin D deficiency in young Swedish women with anorexia nervosa

Bone mass and biomarkers in young women with anorexia nervosa: a prospective 3-year follow-up study

INTRODUCTION

Anorexia nervosa (AN) increases the risk of impaired bone health, low areal bone mineral density (aBMD), and subsequent fractures. This prospective study investigated the long-term effects of bone and mineral metabolism on bone and biomarkers in 22 women with AN.

MATERIALS AND METHODS

Body composition and aBMD were measured by dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography. Total and free 25-hydroxyvitamin D (25OHD), C-terminal collagen cross-links (CTX), osteocalcin, bone-specific alkaline phosphatase (BALP), leptin, sclerostin, and oxidized/non-oxidized parathyroid hormone (PTH) were analyzed before and after 12 weeks of intensive nutrition therapy and again 3 years later. An age-matched comparison group of 17 healthy women was recruited for the 3-year follow-up.

RESULTS

Body mass index (BMI) and fat mass increased from baseline to 3 years in women with AN. Sclerostin decreased during nutrition therapy and further over 3 years, indicating reduced bone loss. CTX was elevated at baseline and after 12 weeks but decreased over 3 years. BALP increased during nutrition therapy and stabilized over 3 years. Free 25OHD was stable during treatment but decreased over 3 years. Non-oxidized PTH was stable during treatment but increased over 3 years. Trabecular volumetric BMD in AN patients decreased during the first 12 weeks and over 3 years despite stable BMI and bone biomarkers implying increased BMD.

CONCLUSION

Our findings highlight the importance of early detection and organized long-term follow-up of bone health in young women with a history of AN.

Hyperphosphatemia during nutrition recovery in patients with severe anorexia nervosa

INTRODUCTION

Anorexia nervosa (AN) is a disorder associated with many medical complications. Regarding phosphorus metabolism, the only recognized alteration is hypophosphatemia associated with refeeding syndrome. However, in our clinical practice, we have observed a high frequency of hyperphosphatemia in late phases of nutrition therapy in severely undernourished AN patients, which has barely been described.

MATERIALS AND METHODS

We carried out a retrospective study of patients with AN hospitalized for severe decompensation of the disease.

RESULTS

Eleven patients were included, all women, with a median age of 23 years [20-46] and a body mass index at admission of 12.2 kg/m² [11.7-13.1]. Hyperphosphatemia was noted in 9 of the 11 cases (81.8%) with a median time to onset of 53 days [30-75]. The median peak serum phosphorus (P) level was 5.1 mg/dl [4.9-5.4]. An inverse relationship was found between the increase in P levels and phosphorus supplementation at the onset of admission. The magnitude of the P increase was associated with the body weight gain achieved during nutrition therapy.

CONCLUSION

Late hyperphosphatemia during nutrition therapy in severely undernourished AN patients affects more than 80% of cases. Body weight gain throughout nutrition therapy is a predictor of increased P levels.

Impulsivity and eating disorders: The relationship between serum 25-hydroxyvitamin D and different impulsivity facets in a transdiagnostic sample

OBJECTIVES

Eating disorders (EDs) are severe psychiatric conditions characterised by malnutrition, dysfunctional behaviours, and hypovitaminosis D. In various psychiatric conditions, including EDs, preliminary evidence has correlated impulsivity to a low level of 25-hydroxyvitamin D [25(OH)D]. This study aims to reinforce this evidence by examining different facets, both behavioural and psychological, of the impulsivity construct in patients with ED.

METHODS

A sample of 119 women was evaluated with a validated questionnaire and computerised neuropsychological tasks: the UPPS-P impulsive behaviour scale, a go/no-go task, and the Balloon Analogue Risk Task (BART). A clinical evaluation for EDs and blood sample collection were also performed to assess specific psychopathology and determine the serum level of 25(OH)D.

RESULTS

Significant correlations were found between serum levels of 25(OH)D and BART scores (p = 0.012) and lack of perseverance (p = 0.034). Moreover, regression analyses showed that higher BART scores may be explained by hypovitaminosis D and higher levels of lack of perseverance in patients with EDs.

CONCLUSIONS

The specific aspect of impulsivity linked to goal strategy and behaviours may be explained in patients with EDs by hypovitaminosis D. A possible connection to the brain inflammatory system is also discussed, along with possible directions for future research.

Anorexia Nervosa and Osteoporosis

Patients with anorexia nervosa (AN) often experience low bone mineral density (BMD) and increased fracture risk, with low body weight and decreased gonadal function being the strongest predictors of the observed bone mineral deficit and fractures. Other metabolic disturbances have also been linked to bone loss in this group of patients, including growth hormone resistance, low insulin-like growth factor-1 (IGF-1) concentrations, low leptin concentrations, and hypercortisolemia. However, these correlations lack definitive evidence of causality. Weight restoration and resumption of menstrual function have the strongest impact on increasing BMD. Other potential treatment options include bisphosphonates and teriparatide, supported by data from small clinical trials, but these agents are not approved for the treatment of low BMD in adolescents or premenopausal women with AN.

Analysis of vitamin D metabolic markers by mass spectrometry: Recent progress regarding the "gold standard" method and integration into clinical practice

Liquid chromatography/tandem mass spectrometry is firmly established today as the gold standard technique for analysis of vitamin D, both for vitamin D status assessments as well as for measuring complex and intricate vitamin D metabolic fingerprints. While the actual mass spectrometry technology has seen only incremental performance increases in recent years, there have been major, very impactful changes in the front- and back-end of MS-based vitamin D assays; for example, the extension to new types of biological sample matrices analyzed for an increasing number of different vitamin D metabolites, novel sample preparation techniques, new powerful chemical derivatization reagents, as well the continued integration of high resolution mass spectrometers into clinical laboratories, replacing established triple-quadrupole instruments. At the same time, the sustainability of mass spectrometry operation in the vitamin D field is now firmly established through proven analytical harmonization and standardization programs. The present review summarizes the most important of these recent developments.

Directly measured free and total 25-hydroxyvitamin D levels in relation to metabolic health in multi-ethnic postmenopausal females in Saudi Arabia

BACKGROUND

Measurement of free 25-hydroyvitamin D (25(OH)D) status has been suggested as a more representative marker of vitamin D status than that of total 25(OH)D. Previously, free 25(OH)D could only be calculated indirectly; however, a newly developed direct assay for the measurement of free 25(OH)D is now available. The aim of this study therefore was to investigate directly measured total and free vitamin D levels association with metabolic health in postmenopausal healthy women living in Saudi Arabia.

METHODS

A sample of 302 postmenopausal women aged ≥50 years (n = 302) living in Saudi Arabia were recruited in a cross-sectional study design. Blood samples were collected from subjects for measurement of serum levels of total 25(OH)D, directly measured free 25(OH)D, metabolic bone parameters, lipid profile, and other biochemical tests.

RESULTS

A positive correlation was found between directly measured free and total 25(OH)D (r = 0.64, P< 0.0001). Total but not free 25(OH)D showed significant association with serum intact parathyroid hormone (P = 0.004), whilst free 25(OH)D but not total 25(OH)D showed a significant association with total cholesterol and LDL-C (P = 0.032 and P = 0.045, respectively).

CONCLUSIONS

Free 25(OH)D and total 25(OH)D were found to be consistently correlated but with different associations to metabolic health parameters. Further research is needed to determine which marker of vitamin D status would be the most appropriate in population studies.

Modestly degraded microarchitecture and high serum levels of osteopontin in Swedish females with anorexia nervosa

PURPOSE

Adult women with long-time anorexia nervosa (AN) are believed to have osteopenia (T-score ≤ 1.0) in 93 % and osteoporosis (T-score ≤ 2.5) in 38 %. Bone microarchitecture assessed by Trabecular Bone Score (TBS) predicts osteoporotic fractures. Our aim was to evaluate the microarchitecture in adult females with AN by determining TBS and to identify factors potentially associated with TBS, such as bone turnover markers.

METHODS

20 female patients with AN (DSM IV), aged 27.8 ± 4.4 years, BMI 16.6 ± 0.6 kg/m² and duration of illness of 8.5 ± 5 years had previously been evaluated with dual-energy X-ray absorptiometry (DXA). TBS measurements were now obtained, using iNsight software, from spinal DXA images. Serum levels of bone turnover markers were determined in patients and healthy normal-weight controls.

RESULTS

Compared to controls serum values of osteopontin were higher (p = 0.009). BMD in patients with AN was reduced by at least 1.0 SD at one or more skeletal sites in 65 % of patients and by at least 2.5 SD in 20 %. Only one of the patients (5%) had suffered a fracture. TBS (mean 1.35 ± 0.06; median 1.36 (1.23-1.44) was in the lower normal range (≥ 1.35). 40 % of patients showed partially (> 1.20 and < 1.35) but none showed a fully degraded micro-architecture.

CONCLUSIONS

In Swedish AN patients we found a low reduction of BMD and fracture history. The bone microarchitecture, evaluated for the first time for this group by TBS, was only modestly compromised, and to a lesser extent than expected for this group of patients with AN.

LEVEL OF EVIDENCE

Level V; cross-sectional descriptive study.

Vitamin D Level Trajectories of Adolescent Patients with Anorexia Nervosa at Inpatient Admission, during Treatment, and at One Year Follow Up: Association with Depressive Symptoms

(1) Background: Evidence has accumulated that patients with anorexia nervosa (AN) are at higher risk for vitamin D deficiency than healthy controls. In epidemiologic studies, low 25(OH) vitamin D (25(OH)D) levels were associated with depression. This study analyzed the relationship between 25(OH)D serum levels in adolescent patients and AN and depressive symptoms over the course of treatment. (2) Methods: 25(OH)D levels and depressive symptoms were analyzed in 93 adolescent (in-)patients with AN from the Anorexia Nervosa Day patient versus Inpatient (ANDI) multicenter trial at clinic admission, discharge, and 1 year follow up. Mixed regression models were used to analyze the relationship between 25(OH)D levels and depressive symptoms assessed by the Beck Depression Inventory (BDI-II). (3) Results: Although mean 25(OH)D levels constantly remained in recommended ranges (≥50 nmol/L) during AN treatment, levels decreased from (in)patient admission to 1 year follow up. Levels of 25(OH)D were neither cross-sectionally, prospectively, nor longitudinally associated with the BDI-II score. (4) Conclusions: This study did not confirm that 25(OH)D levels are associated with depressive symptoms in patients with AN. However, increasing risks of vitamin D deficiency over the course of AN treatment indicate that clinicians should monitor 25(OH)D levels.

Vitamin D3 as possible diagnostic marker of Eating Disorders

Purpose

Eating Disorders (EDs) refer to a group of psychiatric conditions in which disorderly food intake results in impaired psychological functioning or physical health. Nowadays, these disorders represent an increasing problem in modern society. There are no universally validated clinical parameters to confirm, disprove or simply help to identify EDs except for diagnostic criteria on psychiatric basis. The aim of this study was the assessment of Vitamin D3 level in patients with EDs to understand if it might be a valid clinical biochemistry parameter useful as prognostic marker.

Methods

The sample consists of 28 female patients, who suffer from EDs. Blood samples were examined in terms of blood count, glucose, cholesterol and Vitamin D3 levels. The other clinical biochemistry parameters were analysed to understand if the Vitamin D3 was the only altered parameter.

Results

The parameters that appear altered are glycemia, cholesterol and, in particular, Vitamin D3. Significant results were obtained comparing controls with restrictive-type anorexia nervosa (p value= 0,003) and with purging-type anorexia nervosa (p value= 0,007).

Conclusion

There are currently no universally validated and diagnostic reliable clinical biochemistry parameters for EDs but, in the light of the findings, but our research indicates the potential use of Vitamin D3 as a biomarker for anorexia nervosa.

Level of evidence

Level III: Evidence obtained from a single-center cohort study.

[Anorexia nervosa: Abnormalities in hematological and biochemical parameters]

Abnormalities of hematological and biochemical parameters are various and frequent during anorexia nervosa, and are mainly related to malnutrition, weight loss, and compensatory purgative behaviors. They are most often moderate and reversible through appropriate nutritional and weight rehabilitation, as well as well-conducted symptomatic treatment. Severe abnormalities are rarer, but are potentially serious or even fatal. Isolated moderate anemia and leukopenia are frequently noted, with thrombocytopenia being less frequent. Severe, bi-cytopenic, pancytopenic, and spinal cord injury are less common. They can be explained by the gelatinous transformation of the bone marrow caused by malnutrition. Biochemical abnormalities are typically hydroelectrolytic disorders (hypokalemia, hyponatremia, metabolic alkalosis), acute or chronic renal failure, elevated transaminases, risk of potentially severe hypoglycemia, and elevated lipid parameters. During the refeeding syndrome, hypophosphatemia is characteristic and may be associated with hypomagnesemia and hypocalcemia, and thiamine deficiency. Malnutrition can also lead to alterations in hormone status, including hypothyroidism, hypercorticism and hypogonadism, which may be involved in the development of serious bone conditions such as osteoporosis. These abnormalities should be routinely investigated, monitored, and corrected during anorexia nervosa. Early and multidisciplinary management of this eating disorder is essential to prevent chronicity of the disorder and the potential severity of these abnormalities.

Associations of vitamin D with novel and traditional anthropometric indices according to age and sex: a cross-sectional study in central southern China

PURPOSE

Vitamin D insufficiency and obesity are recognized as worldwide concerns and have been linked with each other. New anthropometric indices reflect visceral obesity better than traditional anthropometric indices. Our aim was to identify the specific correlations of novel and traditional anthropometric indices with 25-hydroxyvitamin D (25(OH)D) concentrations by sex and age.

METHODS

Cross-sectional data on sociodemographic characteristics, lifestyle factors, clinical characteristics and biochemical measurements were collected for 12,617 Chinese adults. Four traditional anthropometric indices, body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR), and two novel anthropometric indices, body roundness index (BRI) and body shape index (ABSI), were calculated.

RESULTS

In both sexes, the mean values of BMI, WC, WHtR and BRI tended to increase with 25(OH)D insufficiency, regardless of adjustment (all P < 0.05). Males with insufficient 25(OH)D had increased odds of obesity (assessed by BMI, WC, WHtR, BRI and ABSI) compared to the odds of males with sufficient 25(OH)D. Females with insufficient 25(OH)D had a higher chance of general obesity (assessed by BMI). Low 25(OH)D status was associated with indicators of obesity only in participants aged 45-64 years in both sexes.

CONCLUSION

A inverse association between obesity and lower vitamin D levels was found. Moreover, in addition to BMI, novel indicators of visceral adiposity, such as BRI and ABSI, were associated with lower 25(OH)D serum concentrations in males. The effects of optimizing vitamin D levels in obese Chinese adults need further examination, particularly in middle-aged males.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Adipokines in anorexia nervosa: A systematic review and meta-analysis

OBJECTIVE

The association between adipokine dysregulation and weight loss of patients with anorexia nervosa (AN) has been long investigated, in search of a causal relationship. We sought to: a) synthesize the available evidence on potential differences between AN patients and controls with regards to adipokine measurements (namely, leptin, adiponectin, resistin, soluble leptin receptor, visfatin, vaspin and omentin), b) estimate the potential differences between constitutionally thin (CT) subjects and AN patients, and c) present the available evidence with regards to biomarker efficacy of adipokines in AN.

METHODS

A structured literature search, last updated in 2/2019, was conducted in the following databases: MEDLINE, clinicaltrials.gov, PsycINFO, PSYNDEX and WHO Registry Network. The primary outcome was the standardized mean difference of each adipokine between AN patients and controls of normal BMI. Secondary outcomes included the correlation of leptin with BMI and bone mineral density among AN patients. The study protocol is published in PROSPERO (CRD42018116767).

RESULTS

In a total of 622 screened studies, after exclusion of non-relevant articles and duplicates, 84 reports on leptin, 31 reports on adiponectin, 12 on resistin, 10 on soluble leptin receptor, 5 on visfatin, 3 on vaspin and omentin were finally included in the meta-analysis. Publication bias assessment underlined the possibility of non-significant studies being underrepresented; still, significant heterogeneity renders this statement inconclusive. Leptin [ELISA: SMD (95% CI): -3.03 (-4, -2.06)], radioimmunoassay [RIA: -3.84 (-4.71, -2.98)] and resistin [-1.67 (-2.85, -0.48)] were significantly lower in patients with AN compared with controls, whereas visfatin decrease did not reach significance (-2.03 (-4.38, 0.3). Mean adiponectin, vaspin and soluble leptin receptor levels were significantly higher. In subgroup analysis, a significantly attenuated SMD was reported in ELISA studies compared with RIA studies. Leptin was significantly lower in AN patients compared to CT subjects and BMI marginally did not appear to confound the result. In all analyses, except for the correlation of leptin with BMI in AN patients, high heterogeneity was present. Meta-regression analysis indicated a potential confounding action of controls' BMI and age on leptin SMD and between-assay differences. Publication bias assessment underlined the possibility of nonsignificant studies being underrepresented; still, further investigation did not corroborate this and significant heterogeneity renders this statement inconclusive.

CONCLUSION

A distinct profile of adipokine dysregulation is apparent in AN patients, following the anticipated pattern of low BMI. A precise estimation of the magnitude is hindered by heterogeneity, partly caused by varying assays and methodologies. Interestingly, while mean leptin levels are lower in AN subjects compared with constitutionally thin women, there is an overlap in individual levels between the two groups and therefore, they cannot be used to differentiate between these states.

Low PTH Levels in Adolescents With Anorexia Nervosa

Introduction: Patients with anorexia nervosa (AN) experience medical complications including impaired bone metabolism, increased fracture rate, kidney stones and chronic renal failure. However, the mechanisms of such complications are not fully understood. Healthy adolescents have been shown to have higher PTH levels when compared with pre-pubertal children and adults. Given the importance of central measures of calcium and vitamin D metabolism in bone and kidney health, 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) have been extensively investigated in patients with AN, however none of the previous studies accounted for age-specific reference ranges for PTH. The aim of this study was to investigate central measures of calcium and vitamin D metabolism in adolescents with newly diagnosed AN using age-specific reference ranges and to determine whether any significant abnormalities required further study. Methods: This was a cross-sectional study of 61 adolescents (mean age = aged 15.2 ± 1.56 years) with newly diagnosed AN, referred to a tertiary center over a period of 2 years. Demographic, auxiological, and nutrient (vitamin D and calcium) intake data was obtained. Central measures of calcium and vitamin D metabolism in blood and urine were investigated. PTH results were compared with age-specific reference ranges from the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER). Descriptive statistics and correlation analysis were performed. Results: Low PTH levels were observed in 35% of the cohort. Overall, serum calcium, phosphate and 25OHD were within the reference range. Using loess curves, PTH had a significant negative and non-linear correlation with 25OHD with an inflection point at a 25OHD level of 100 nmol/l, above which the association was no longer present. Correlation analysis did not show a significant association between PTH and total or corrected serum calcium, urine calcium/creatinine (Ca/Cr) ratio, total dietary calcium intake, magnesium or Tanner staging. Conclusion: PTH levels were reduced in approximately a third of adolescents with AN. This observation has not been reported given the universal usage of reference ranges that covers all ages. This finding may unmask a potential role for reduced PTH levels in the pathogenesis of kidney stones and bone phenotype in patients with AN.

Eating Disorders During Gestation: Implications for Mother's Health, Fetal Outcomes, and Epigenetic Changes

Introduction: Eating disorders (EDs) have increased globally in women of childbearing age, related to the concern for body shape promoted in industrialized countries. Pregnancy may exacerbate a previous ED or conversely may be a chance for improving eating patterns due to the mother's concern for the unborn baby. EDs may impact pregnancy evolution and increase the risk of adverse outcomes such as miscarriage, preterm delivery, poor fetal growth, or malformations, but the knowledge on this topic is limited. Methods: We performed a systematic review of studies on humans in order to clarify the mechanisms underpinning the adverse pregnancy outcomes in patients with EDs. Results: Although unfavorable fetal development could be multifactorial, maternal malnutrition, altered hormonal pathways, low pre-pregnancy body mass index, and poor gestational weight gain, combined with maternal psychopathology and stress, may impair the evolution of pregnancy. Environmental factors such as malnutrition or substance of abuse may also induce epigenetic changes in the fetal epigenome, which mark lifelong health concerns in offspring. Conclusions: The precocious detection of dysfunctional eating behaviors in the pre-pregnancy period and an early multidisciplinary approach comprised of nutritional support, psychotherapeutic techniques, and the use of psychotropics if necessary, would prevent lifelong morbidity for both mother and fetus. Further prospective studies with large sample sizes are needed in order to design a structured intervention during every stage of pregnancy and in the postpartum period.

Comparison of free and total 25-hydroxyvitamin D in normal human pregnancy

Vitamin D status correct monitoring during pregnancy is critically important for both maternal and fetal health. 25-Hydroxyvitamin D (25(OH)D) - a prohormone of a biologically active 1,25-dihydroxyvitamin D (1,25(OH)₂D), despite the lack of biological activity, during the past decades has been routinely used as a main biomarker characterizing vitamin D status. About 85% of 25(OH)D in the bloodstream is bound to its specific carrier - vitamin D-binding protein (DBP), the remaining 15% are loosely bound to albumin, and only less than 0.1% are free in the circulation ("free 25(OH)D"). Total 25(OH)D is the sum of DBP-bound, albumin-bound and free 25(OH)D. According to a "free hormone hypothesis", only free 25(OH)D is able to induce a biological effect. Normal pregnancy is characterized by elevated serum DBP levels, and due to this fact the diagnostic strength of serum total 25(OH)D has been questioned. Free 25(OH)D might be a better characteristic of vitamin D status in this settings. We aimed to compare the diagnostic strength of a routine total 25(OH)D with directly measured free 25(OH)D in normal pregnancy by comparing the association strength between free and total 25(OH)D with biomarkers of bone health (PTH, calcium, bone-specific alkaline phosphatase (BSAP)), lipid metabolism (adiponectin, LDL, HDL), kidney function (urea), endocrine parameters (T4, T3, TSH), and group B water-soluble vitamins. The study was conducted in 368 healthy white pregnant women - residents of north-east Germany. Free 25(OH)D showed an overall better associations with gestational age, markers of bone metabolism (calcium (rho = 0.141, p = 0.007 with free 25(OH)D; rho = 0.060, p = 0.251 with total 25(OH)D) and BSAP (rho = -0.203, p < 0.001 with free 25(OH)D; rho = -0.108, p = 0.038 with total 25(OH)D), lipid metabolism parameters (adiponectin (rho = 0.142, p = 0.008 with free 25(OH)D; rho = 0.054, p = 0.307 with total 25(OH)D), LDL cholesterol (rho = -0.191, p < 0.001 with free 25(OH)D; rho = 0.033, p = 0.539 with total 25(OH)D)) and a kidney function marker (urea (rho = 0.114, p = 0.032 with free 25(OH)D; rho = 0.008, p = 0.887 with total 25(OH)D)) than total 25(OH)D. In conclusion, the current study revealed that free 25(OH)D is a more precise determinant of the vitamin D status during normal human pregnancy than total 25(OH)D. In the settings of normal pregnancy, free 25(OH)D revealed better associations with markers of bone metabolism (calcium, BSAP), lipid metabolism (adiponectin, LDL cholesterol, LDL/HDL ratio) and kidney function (urea) than total 25(OH)D.

Seasonal variation of BMI at admission in German adolescents with anorexia nervosa

Objective

Recent preliminary studies indicated a seasonal association of BMI at admission to inpatient treatment for anorexia nervosa (AN), indicating lower BMI in the cold season for restrictive AN. An impaired thermoregulation was proposed as the causal factor, based on findings in animal models of AN. However, findings regarding seasonality of BMI and physical activity levels in the general population indicate lower BMI and higher physical activity in summer than in winter. Therefore, we aimed to thoroughly replicate the findings regarding seasonality of BMI at admission in patients with AN in this study.

Method

AN subtype, age- and gender-standardized BMI scores (BMI-SDS) at admission, mean daily sunshine duration and ambient temperature at the residency of 304 adolescent inpatients with AN of the multi-center German AN registry were analyzed.

Results

A main effect of DSM-5 AN subtype was found (F(2,298) = 6.630, p = .002), indicating differences in BMI-SDS at admission between restrictive, binge/purge and subclinical AN. No main effect of season on BMI-SDS at admission was found (F(1,298) = 4.723, p = .025), but an interaction effect of DSM-5 subtype and season was obtained (F(2,298) = 6.625, p = .001). Post-hoc group analyses revealed a lower BMI-SDS in the warm season for restrictive AN with a non-significant small effect size (t(203.16) = 2.140, p = .033; Hedges′g = 0.28). Small correlations of mean ambient temperature (r = −.16) and daily sunshine duration (r = −.22) with BMI-SDS in restrictive AN were found. However, the data were widely scattered.

Conclusions

Our findings are contrary to previous studies and question the thermoregulatory hypothesis, indicating that seasonality in AN is more complex and might be subject to other biological or psychological factors, for example physical activity or body dissatisfaction. Our results indicate only a small clinical relevance of seasonal associations of BMI-SDS merely at admission. Longitudinal studies investigating within-subject seasonal changes might be more promising to assess seasonality in AN and of higher clinical relevance.