Smoke and Mirrors

Here's one of those studies I just have to shake my head at.  It's one of the countless "low-fat" diet interventions that have been done since the 1980s.  Here the subjects were split into two groups, a low-fat diet and a low-fat diet plus exercise.

Both groups lost weight over the 12 week study.  So is the low-fat diet the answer to losing weight?  No, no, and no.  First off, any dramatic shift in diet is bound to have an effect on the body.  If a person suddenly switches to a low-fat or low-carbohydrate diet, they will lose weight.  Yet the weight will always come back.

Walter Willett, from the Harvard School of Public Health, says this nicely in one of his papers, "Dietary fat is not a major determinant of body fat": "In short-term trials, a modest reduction in body weight is typically seen in individuals randomized to diets with a lower percentage of calories from fat. However, compensatory mechanisms appear to operate, because in randomized trials lasting >or=1 year, fat consumption within the range of 18% to 40% of energy appears to have little if any effect on body fatness."

In other words, if you deprive the body of what it needs it will compensate and adjust over time.  None of these low-fat diets (or any other diets) show any significant weight loss over a couple of years.

I think history will judge this time period and the dietary studies being performed fairly harshly.  Researchers have known for many years now that diets aren't the answer to long-term weight loss.  Yet people keep cranking out these studies trying to defend their turf.  In the meantime, the US population gets heavier and heavier and the medical costs continue to rise.