Physical activity and dietary intake in BMI discordant identical twins.
Despite the latest discovery of obesity-associated genes, the rapid rise in global obesity suggests a major role for environmental factors. This study investigated the influence of environmental factors on physical activity and dietary intake independent of genetic effects.



Sixteen female monozygotic twins aged 48.8 ± 9.8 years (range 37-70) with a mean BMI discordance of 3.96 ± 2.1 kg/m(2) (range 0.7-8.2) were studied. Physical activity was determined using 7-day accelerometry and dietary intake using 3-day 24-h recalls.



Heavier cotwins were generally less physically active (mean activity counts × 1,000 per day ± SD; 505.5 ± 155.1 vs. 579.6 ± 185.4, P = 0.047) and tended to spend 6.1 min/day less in moderate to vigorous physical activity than leaner cotwins (P = 0.09). Energy intake did not significantly differ within pairs. Total fat intake (en%; P = 0.03), specifically monounsaturated fat (P < 0.01) and polyunsaturated fat (P = 0.08), was higher in the heavier cotwins.



After eliminating genetic effects, higher BMI is associated with lower overall and moderate to vigorous physical activity and higher intake of total fat, although the direction of causality cannot be determined. Future identification of the environmental factors responsible for these findings might contribute to developing new strategies in managing obesity.
Department of Internal Medicine, VU University Medical Centre, Amsterdam, the Netherlands.|EMGO+ Institute for Health and Care Research, VU University Medical Centre, Amsterdam, the Netherlands.
Stieneke
S
Doornweerd
Department of Internal Medicine, VU University Medical Centre, Amsterdam, the Netherlands.
Richard G
RG
IJzerman
EMGO+ Institute for Health and Care Research, VU University Medical Centre, Amsterdam, the Netherlands.|Department of Health Sciences, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, the Netherlands.
Lotte
L
van der Eijk
EMGO+ Institute for Health and Care Research, VU University Medical Centre, Amsterdam, the Netherlands.|Department of Health Sciences, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, the Netherlands.
Judith E
JE
Neter
EMGO+ Institute for Health and Care Research, VU University Medical Centre, Amsterdam, the Netherlands.|Department of Biological Psychology, VU University Amsterdam, Amsterdam, the Netherlands.
Jenny
J
van Dongen
EMGO+ Institute for Health and Care Research, VU University Medical Centre, Amsterdam, the Netherlands.|Department of Public and Occupational Health, VU University Medical Centre, Amsterdam, the Netherlands.
Hidde P
HP
van der Ploeg
EMGO+ Institute for Health and Care Research, VU University Medical Centre, Amsterdam, the Netherlands.|Department of Biological Psychology, VU University Amsterdam, Amsterdam, the Netherlands.
Eco J
EJ
de Geus
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004032:Diet; D015444:Exercise; D005260:Female; D006801:Humans; D008875:Middle Aged; D011795:Surveys and Questionnaires; D014430:Twins, Monozygotic