Although trends in fat intake have been found to correlate closely with trends in cardiovascular disease, several studies have demonstrated that obesity is increasing at the same time that fat intake is decreasing (7). In fact, some of the countries that have experienced a substantial decrease in fat intake have noted the most dramatic increases in obesity prevalences. In Finland, for instance, prevalence of obesity rose from 10% to 14% in men and from 10% to 11% in women between the late 1970s and early 1990s (8) while at the same time fat intake decreased from approximately 38% to 34% (3). In the USA, data from the National Health and Nutrition Examination Survey (NHANES) show that while fat intake was decreasing, prevalences of severe obesity increased from 10% to 20% in men and from 15% to 25% in women (9). Although the possibility of ecological fallacy must be considered when interpreting such results, it cannot be excluded that the secular trends in obesity may have been even more dramatic if not for the decrease in fat intake.
Figure 10.1 shows trends in fat intake and obesity among adult Americans (9,10).
There are at least three interpretations for this paradox of opposite trends for fat intake and obesity. One is that people are decreasing their energy intake but also becoming less active. Another is that people are maintaining their energy intake despite the reduction in fat intake. A third explanation, is that fat intakes are not as low as reported. With regard to the first alternative, data from England have implicated sedentary activity as the most plausible explanation. For instance, trends in number of cars, or number of televisions per household, were more closely associated with the dramatic increase in severe obesity seen in England
over the past two decades, than were trends in fat or energy intake (11). With regard to the second alternative, it has been suggested that total energy may well remain high, despite the proliferation of low fat products on the market. This may be due to the misperception that low fat products can be consumed without restraint (12). Finally, with regard to the third alternative, social desirability bias may cause people increasingly to report false low fat intakes, as official recommendations and public health campaigns to reduce fat intake are intensified and disseminated.
the obese is that the diet-obesity and diet-health associations may be distorted (16). In addition, diet-obesity associations found in dietary surveys may not reflect those found in the general population, since non-responders generally are more likely to be obese, more likely to be smokers, more likely to have a low educational level (17), and may have a different dietary consumption pattern than respon-ders. Finally, older food databases may not sufficiently capture nutrient composition of these new low fat products, and hence, add to the creation of biased diet-obesity relationships.
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