Surveys of food intake in humans, following measurements of energy expenditures in free-living persons, obtained by the doubly-labeled water technique, have been severely questioned in recent years. The present article reviews studies performed in both adults and children, comparing energy intake and expenditures in the same individuals. In adults, reported intake is often insufficient to cover minimal energy needs. The typical level of "under-reporting" is about 20%, and it is even higher in obese subjects. Intake data obtained from children are more valid than data from adults. Different survey methods yield differing degrees of agreement between intake and expenditure measurements using the doubly labeled water technique: frequency questionnaires tend to induce over-reporting, whereas the classical 24 hours recall is very susceptible to large under-reporting. Even obese adults can provide accurate reports of their daily food intake if properly trained and motivated. The interpretation of data obtained with the doubly labeled water method should integrate the considerable day-to-day variations observed in human food intake.
doubly-labeled water method; food intake surveys; epidemiology; energy intake; energy expenditures