title: Fragmentation of daily rhythms associates with obesity and cardiorespiratory fitness in adolescents: The HELENA study.
abstract: Chronobiology studies periodic changes in living organisms and it has been proposed as a promising approach to investigate obesity. We analyze the association of the characteristics of the rest-activity rhythms with obesity, cardiorespiratory fitness and metabolic risk in adolescents from nine European countries.
  
  
  
  1044 adolescents (12.5-17.5 y) were studied. Circadian health was evaluated by actigraphy with accelerometers (Actigraph GT1M). Characteristics of the daytime activity such as fragmentation (intradaily variability), estimated acrophase, and 10 h mean daytime activity index were obtained. Body composition was assessed using Bioelectrical-Impedance-Analysis, skinfold thickness, air-displacement-plethysmography and Dual-energy-X-ray-Absorptiometry. Cardiorespiratory fitness (VO2max) and metabolic risk were studied.
  
  
  
  Highly fragmented activity rhythms were associated with obesity and central adiposity (P < 0.05). Obese adolescents had ∼3 times higher odds of having a high fragmentation of daytime activity compared to normal weight adolescents OR (95% CI) = 2.8 (1.170, 6.443). A highly fragmented rhythm was also related to lower cardiorespiratory fitness and higher metabolic risk (P < 0.05) so those adolescents classified as low fitness showed a significantly higher fragmentation of daytime activity than those included in the high fitness group (P < 0.0001). Other characteristics of the rhythms such as smaller 10 h daytime mean activity index and delayed estimated acrophase were also related to obesity and metabolic risk (P < 0.05).
  
  
  
  Our results indicate that the daily organization of the rest-activity cycle is more fragmented in obese and less fit adolescents and correlates with higher metabolic risk. This fact reinforces our hypothesis that disturbances in daily rhythms can be considered as sensitive markers of poorer adolescent's health.
authors.affiliation: Chronobiology Laboratory, Department of Physiology, University of Murcia and Research Biomedical Institute of Murcia (IMIB), Murcia, Spain. Electronic address: garaulet@um.es.
authors.forename: Marta
authors.initials: M
authors.lastname: Garaulet
authors.affiliation: Chronobiology Laboratory, Department of Physiology, University of Murcia and Research Biomedical Institute of Murcia (IMIB), Murcia, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Martinez-Nicolas
authors.affiliation: PROFITH "PROmoting FITness and Health Through Physical Activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Spain; Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
authors.affiliation: Department of Chronic Diseases, Centre of Health and Behavioral Sciences, National Institute for Health Development, Tallinn, Estonia.
authors.forename: Kenn
authors.initials: K
authors.lastname: Konstabel
authors.affiliation: Department of Nutrition and Food Science, University of the Basque Country, Vitoria, Spain.
authors.forename: Idoia
authors.initials: I
authors.lastname: Labayen
authors.affiliation: Department of Health and Human Performance, Facultad de Ciencias de la Actividad Física y del Deporte, Universidad Politécnica de Madrid, Madrid, Spain.
authors.forename: Marcela
authors.initials: M
authors.lastname: González-Gross
authors.affiliation: Immunonutrition Research Group, Department of Metabolism and Nutrition, Instituto del Frio, Institute of Food Science, Technology and Nutrition (ICTAN), Spanish National Research Council (CSIC), Madrid, Spain.
authors.forename: Ascensión
authors.initials: A
authors.lastname: Marcos
authors.affiliation: Department of Paediatrics, Medical Faculty, University of Pécs, József A, Pécs, Hungary.
authors.forename: Dénes
authors.initials: D
authors.lastname: Molnar
authors.affiliation: Division of Clinical Nutrition and Prevention, Department of Pediatrics, Medical University of Vienna, Vienna, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Widhalm
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Universidad de Zaragoza, Spain; Faculty of Health and Sport Science (FCSD), Department of Physiotherapy and Nursing, Universidad de Zaragoza, Huesca, Spain.
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Casajús
authors.affiliation: Department of Public Health, Ghent University, Ghent, Belgium.
authors.forename: Stefaan
authors.initials: S
authors.lastname: De Henauw
authors.affiliation: Preventive Medicine and Nutrition Unit, University of Crete, School of Medicine, Heraklion, Crete, Greece.
authors.forename: Anthony
authors.initials: A
authors.lastname: Kafatos
authors.affiliation: Institut für Ernährungs- und Lebensmittelwissenschaften - Humanernährung, Rheinische Friedrich-Wilhelms Universität, Bonn, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Breidenassel
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Sjöström
authors.affiliation: Department of Medical Physiology, Faculty of Medicine, University of Granada, Granada, Spain.
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Castillo
authors.affiliation: GENUD "Growth, Exercise, NUtrition and Development" Research Group, Universidad de Zaragoza, Spain; Faculty of Health Science (FCS), Department of Physiotherapy and Nursing, Universidad de Zaragoza, Zaragoza, Spain; Department of Preventive Medicine, Faculty of Medicine, University of Sao Paulo, Brazil.
authors.forename: Luis A
authors.initials: LA
authors.lastname: Moreno
authors.affiliation: Chronobiology Laboratory, Department of Physiology, University of Murcia and Research Biomedical Institute of Murcia (IMIB), Murcia, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Madrid
authors.affiliation: PROFITH "PROmoting FITness and Health Through Physical Activity" Research Group, Department of Physical Education and Sports, Faculty of Sport Sciences, University of Granada, Spain; Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden.
authors.forename: Francisco B
authors.initials: FB
authors.lastname: Ortega
mesh_terms: D050154:Adiposity; D000293:Adolescent; D001823:Body Composition; D015992:Body Mass Index; D000072599:Cardiorespiratory Fitness; D002648:Child; D002784:Cholesterol / Q000097:blood; D002909:Chronobiology Phenomena; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005060:Europe; D015444:Exercise; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008962:Models, Theoretical; D009765:Obesity / Q000378:metabolism*; D012307:Risk Factors; D012885:Skinfold Thickness; D012959:Socioeconomic Factors; D014280:Triglycerides / Q000097:blood; D055105:Waist Circumference
chemical_list: D007328:Insulin; D014280:Triglycerides; D002784:Cholesterol
keywords: Adolescents; Cardiorespiratory fitness; Daily; Obesity; Rest-activity rhythms