Inaccuracies in food and physical activity diaries of obese subjects: complementary evidence from doubly labeled water and co-twin assessments

Int J Obes (Lond). 2010 Mar;34(3):437-45. doi: 10.1038/ijo.2009.251. Epub 2009 Dec 15.


Objective: To study whether eating or physical-activity (PA) habits differ between obese and non-obese monozygotic (MZ) co-twins independent of genetic effects.

Methods: Rare MZ pairs discordant for obesity (n=14, body mass index difference 5.2+/-1.8 kg m(-2)) and weight-concordant control pairs (n=10, 1.0+/-0.7 kg m(-2)), identified through a population-based registry of 24-28-year-old twins (n=658 MZ pairs), completed 3-day food and PA diaries and eating behavior questionnaires. Each twin was asked to compare his/her own eating and PA patterns with the co-twin's behavior by structured questionnaires. Accuracy of energy intake was validated by doubly labeled water.

Results: Non-obese co-twins consistently reported that their obese twin siblings ate more food overall, consumed less healthy foods and exercised less than the non-obese co-twins do. However, no differences in energy intake (9.6+/-1.0 MJ per day vs 9.8+/-1.1 MJ per day, respectively) in the food diaries or in the mean PA level (1.74+/-0.02 vs 1.79+/-0.04, respectively) in the PA diaries were found between obese and non-obese co-twins. A considerable underreporting of energy intake (3.2+/-1.1 MJ per day, P=0.036) and overreporting of PA (1.8+/-0.8 MJ per day, P=0.049) was observed in the obese, but not in the non-obese co-twins.

Conclusions: On the basis of rare MZ twin pairs discordant for obesity, the co-twin assessments confirmed substantial differences in eating and PA behavior between obese and non-obese persons. These may be overlooked in population studies using food and PA diaries because of considerable misreporting by the obese.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Twin Study

MeSH terms

  • Adult
  • Body Mass Index
  • Diet Records
  • Energy Intake*
  • Energy Metabolism
  • Exercise*
  • Feeding Behavior / psychology*
  • Female
  • Humans
  • Male
  • Motor Activity
  • Obesity / epidemiology
  • Obesity / psychology*
  • Records / standards*
  • Truth Disclosure
  • Twins, Monozygotic / psychology*
  • Young Adult