Monday, July 16, 2012

Under-reporting of food intake and exercise

Discrepancy between Self-Reported and Actual Caloric Intake and Exercise in Obese Subjects
Steven W. Lichtman, Ed.D., Krystyna Pisarska, M.S., Ellen Raynes Berman, Psy.D., Michele Pestone, M.S., Hillary Dowling, Ph.D., Esther Offenbacher, Ed.D., Hope Weisel, M.S., R.D., Stanley Heshka, Ph.D., Dwight E. Matthews, Ph.D., and Steven B. Heymsfield, M.D.
N Engl J Med 1992; 327:1893-1898December 31, 1992
[Discussion Section] The main finding of this study is that failure to lose weight despite a self-reported low caloric intake can be explained by substantial misreporting of food intake and physical activity. The underreporting of food intake by the subjects in group 1 even occurred 24 hours after a test meal eaten under standardized conditions. In contrast, values for total energy expenditure, resting metabolic rate, thermic effect of food, and thermic response to exercise were comparable with those of obese subjects in group 2 who did not report a history of diet resistance.
In addition to their greater degree of misreporting, the subjects in group 1 used thyroid medication more often, had a stronger belief that their obesity was caused by genetic and metabolic factors and not by overeating, and reported less hunger and disinhibition and more cognitive restraint than did the subjects in group 2. Subjects presenting for weight-control therapy who had these findings in association with a history of self-reported diet resistance would clearly convey the impression that a low metabolic rate caused their obesity.
The results of the evaluation of all major aspects of energy metabolism in the subjects in group 1 confirmed that substantial misreporting of food intake and physical activity accounted for the diet resistance they reported. There are, however, physiologic explanations for short-term diet resistance that should be considered in subjects with unexpectedly slow weight loss. Under certain conditions, fluid retention can mask weight loss for up to 16 days in subjects who are actually losing fat through dieting.36 After several weeks of weight loss, energy expenditure decreases and adaptive changes in protein metabolism occur, reducing the degree of negative energy and nitrogen balance and slowing the weight loss until it is almost imperceptible. Also, subjects with undiagnosed or untreated thyroid disease and those taking medications that lower energy expenditure may lose weight slowly.
Misreporting by the subjects in group 1 does not appear to be a facile deception, for several reasons. First, underreporting of food intake has been noted in obese and nonobese subjects with no history of diet resistance.6 7 8 9 , 37 , 38 The mechanisms responsible for this phenomenon are not well understood. Second, the subjects in group 1 participated voluntarily in a complex, time-consuming protocol designed to evaluate the cause of their perceived diet resistance. Several had a history of up to 20 serious diet attempts, and most had had extensive medical evaluations for obesity. Third, the subjects in group 1 were distressed when they were given their study results. Thus, important basic psychological issues require elucidation before this form of diet resistance can be properly understood.
In conclusion, all the obese subjects we studied who had a history of self-reported diet resistance had appropriate energy expenditure, but they misreported their actual food intake and physical activity.
Supported by grants (P01-DK42618, DK-26687, and RR 00047) from the National Institutes of Health.
Presented in part at the annual meeting of the American Federation of Clinical Research, Seattle, May 4–7, 1991.
We are indebted to Mr. Charles Gilker, Ms. Susan Thomas, and Ms. Kathleen Buhl for assistance with the mass-spectroscopic analyses using doubly labeled water; to Dr. William Berman for advice on developing procedures for psychological testing; and to Ms. Judy Dickson for assistance in the preparation of the manuscript.

SOURCE INFORMATION

From the Obesity Research Center, Department of Medicine, St. Luke's–Roosevelt Hospital Center, Columbia University College of Physicians and Surgeons (S.W.L., K.P., E.R.B., M.P., H.D., E.O., H.W., S.H., S.B.H.), and the Departments of Medicine and Surgery, New York Hospital—Cornell Medical Center (D.E.M.), all in New York. Address reprint requests to Dr. Heymsfield at the Weight Control Unit, 411 W. 114th St., New York, NY 10025.

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