Every now and then an overweight patient tells me he can’t lose weight even though his typical daily food intake is two pieces of plain toast, a cup of grapes, a hard-boiled egg, and three celery stalks. That’s 530 calories. Most adults eat between 1200 to 3000 calories a day.
Even if he lays around on a couch all day watching TV with a remote control channel changer, I know my patient’s basal metabolism requires at least 1,000 calories daily to keep him alive. He says he’s eating only 530. His body must have, and will get, the extra 470 calories from his fat stores. Over time, he must lose weight as his body converts his fat into basal metabolic energy to keep him alive.
Yet he swears he’s not losing weight, and, in fact, may be gaining. I don’t believe he’s lying to me. What’s going on here?
The answer is suggested by a study published in the New England Journal of Medicine. Ten similar “diet resistant” obese people – nine women, one man, average weight 189 pounds (86 kg) – were carefully studied by a team of researchers. They were taught to record all food intake over time in a diary. When the foods eaten were totaled up, average self-reported intake was 1,000 calories daily.
A highly accurate method of measuring calorie expenditure, called “doubly labeled water,” proved that average calorie intake was actually 2,000 calories daily. Furthermore, they over-reported their physical activity by 50 percent. The authors of the study note that while many people under-report their caloric intake, the degree of under-reporting is greater in obese people. They admit that “the mechanisms responsible for this phenomenon are not well understood.”
People who just can’t lose weight despite “severe calorie restriction” are in fact eating more calories than they think.
How can we overcome this tendency? One solution is to keep a food journal.
Reference: Lichtman, Steven, et al. Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. New England Journal of Medicine, 327 (1992): 1,893-1,898.