Thursday, November 11, 2010

Apparently nobody's good at keeping food records.

[My heartfelt thanks to all those brave men and women who gave their lives for our freedom]

Food diaries are the mainstay of any behavioural weight management program worth its salt, but are people actually good at keeping them?

We use food diaries at my offices and there's no doubt some folks are better than others, but given the incredible access we have to food, the lack of caloric information in most restaurants, the reluctance of most folks to weigh and measure what they're eating, and the nibbles and bites we may randomly have, accurate record keeping's tough.

A study done nearly a decade ago helps to illustrate how tough.

Simply designed, the study compared the calories recorded in 7 day food diaries with the calories inferred by doubly labeled water testing. The extra wrinkle with this study? Half of the subjects were registered dietitians while half were plain old folk, with the assumption being that the dietitians would be record keeping ringers, especially given the fact that the study was presented to them as a challenge to record their dietary intake with enough accuracy so as not to deviate from the estimate obtained via doubly labeled water.

The results?

First the non-dietitians. Despite actually keeping food records they missed 18% of the calories they consumed. Over 40lbs a year worth.

Now for the dietitians who were trying their best to be perfectly accurate. They missed 10.5% of the calories they consumed. Due to a small sample size, this wasn't deemed statistically significant, but over a year were that discrepancy maintained, they'd have missed 22lbs worth of 'em.

At my office we sometimes ask patients to do what we call, "science experiments" where for a one or two week period they become as anal about record keeping as they possibly can. Weighing and measuring everything. Recording food within minutes of eating it and ideally, not eating out even once. Almost invariably patients who felt they were fairly accurate with their records before the experiment find anywhere from 200-500 calories they didn't even realize were there.

Of course just because something's challenging to do, doesn't mean a person shouldn't do it and if you're trying to lose weight, there's no doubt keeping a food diary has been proven to help.

Remember, food diarizing isn't for judgment. It isn't there to tell you if you've been good or bad, or how much you're allowed, or how much room is left for dinner. What a food diary's for is information, because the more information you have before you make any decision in life, the better that decision's going to be, and knowing how many calories you're having will certainly help you in deciding which ones are worth it and which ones aren't.

Champagne CM, Bray GA, Kurtz AA, Monteiro JB, Tucker E, Volaufova J, & Delany JP (2002). Energy intake and energy expenditure: a controlled study comparing dietitians and non-dietitians. Journal of the American Dietetic Association, 102 (10), 1428-32 PMID: 12396160