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Self-Reported Food Intake May Thwart Research

Mon Mar 22, 5:33 PM ET Add Health - Reuters to My

By Amy Norton

NEW YORK (Reuters Health) - A new study of overweight, diabetic women

casts doubt on the reliability of the self-reported dietary habits

often used in medical research.

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Researchers found that most of the 200 women they studied, as many as

81 percent, reported eating fewer calories than they actually had,

based on objective measures.

Many also claimed to have eating habits that closely matched the

recommended diet for diabetics, which suggests the women were really

reporting what they thought they should be eating, according to the

researchers.

The problem with fibbing about or underestimating calories is that it

makes it hard to measure the true effectiveness of dietary

interventions--a key component of diabetes treatment. The new

findings point to the importance of using some objective measure to

back up research participants' dietary claims, the study authors

report in the March issue of the journal Diabetes Care.

Their study included middle-aged and older African-American women

with type 2 diabetes, most of whom were overweight or obese. Past

research has shown calorie underreporting to be common among women,

people who are overweight, and those who want to lose weight, lead

study author Dr. Carmen D. -Hodge told Reuters Health.

She said people may, for instance, have a hard time remembering what

or how much they ate, or may feel pressured to report eating habits

that are " socially acceptable. "

For the current study, -Hodge and her colleagues at the

University of North Carolina at Chapel Hill compared diabetic women's

reported food intake with objective estimates of their calorie

expenditure. To get these estimates, they had the women wear small

electronic devices called accelerometers, which gauge the number of

calories burned during physical activity, for one week. The

researchers also measured the women's base metabolic rates. These

measures were compared with participants' self-reported dietary

intake on three days.

The idea is that in the absence of weight loss or gain, a person's

calorie intake should roughly equal calorie expenditure. If someone

takes in fewer calories than she burns, she should lose weight.

-Hodge and her colleagues found that most of the women in their

study reported calorie intakes that were lower than their estimated

calorie expenditure.

Based on the accelerometer data, the researchers estimate that 81

percent underreported their calorie intake. This estimate dipped, but

remained high at 58 percent, when the researchers compared calorie

intake with base metabolic rates.

The researchers also found that the heavier a woman was, the more

likely she was to underreport calories.

It's possible, the investigators acknowledge, that many of these

women, who were part of a larger study on managing diabetes with diet

and exercise, truly were cutting calories. But, they note, six months

after the current results were compiled, the women were showing no

significant weight loss.

The " major implication, " the researchers conclude, is that such self-

reports need to be independently validated.

-Hodge said the findings are particularly relevant to studies

of people with type 2 diabetes because of their high prevalence of

obesity.

SOURCE: Diabetes Care, March 2004.