Discrepancy between self-reported and actual caloric intake and exercise in obese subjects.
Level 4 - case-series / case-control
Controlled observational study comparing a small clinical subgroup to controls
PubMed 1454084 · doi:10.1056/NEJM199212313272701
What was done
Researchers evaluated potential mechanisms of self-reported diet resistance (failure to lose weight despite reporting <1200 kcal/day) among 224 consecutive obese individuals presenting for treatment. Ten subjects with a history of diet resistance (Group 1: 9 women, 1 man) underwent 14-day evaluations of actual caloric intake, total energy expenditure, and thermogenic components using indirect calorimetry and body composition analysis. Comparisons were made against control subgroups drawn from 80 subjects without a history of diet resistance (Group 2: 67 women, 13 men).
What was found
Total energy expenditure and resting metabolic rate in Group 1 were within 5% of predicted values for body composition, and thermic effects of food and exercise did not differ significantly between groups. Subjects in Group 1 underreported actual food intake by an average of 47 ± 16% (mean ± SD) and overreported physical activity by 51 ± 75%. Compared with Group 2, Group 1 subjects were significantly more likely to perceive a genetic cause for their obesity, use thyroid medication, and describe eating behavior as relatively normal (all P < 0.05).
Why it matters
This study establishes that self-reported resistance to dietary weight loss is primarily due to substantial underreporting of energy intake and overestimation of physical activity, rather than metabolic or thermogenic defects.
Limits
The detailed metabolic and caloric intake evaluations were conducted in only 10 diet-resistant subjects, of whom only one was male. All participants were treatment-seeking individuals at a clinical center, potentially introducing selection bias.
Cited by
- supports Scientific studies consistently show that people underreport their calorie intake by 30% to 50%.
- supports A 1992 New England Journal of Medicine study on self-reported diet-resistant obese subjects found they reported consuming 1,200 calories per day but actually consumed over 1,800 calories and overreported physical activity by 47%.