In addition to providing insight into how we store a different mix of fatty acids than that which we eat, these observations raise important questions about the nutritional requirements for optimum health of obese and post-obese humans. That is, this sizable group may constitute an important population with unusually high w3 fatty acid needs. Given the conditions that we tend to store less w3 fatty acid than we eat, that we tend to preferentially mobilize and oxidize w3 fatty acids when dieting, and that our North American diet is at best marginal in w3 fatty acids, then it is likely that people who are constantly dieting would be highly prone to the negative effects of w3 deficiency.
Due to the fact that there is a considerable degree of inter-individual variability in tissue fatty acid composition to begin with, plus the extended period (years) for full equilibration of all body lipid pools following a change in dietary fat composition, plus the long latency period to develop some w3 deficiency diseases (e.g., coronary atherosclerosis and cancer), the hypothesis put forward here would be hard to prove in a prospective trial. However two epidemiological studies have demonstrated positive correlations between recurrent weight change and coronary death (6.Hamm, Am J Epidemiol, l989; 7.Lissner, NEJM, l991). This would indicate that frequent attempts at weight loss are potentially dangerous in the context of a marginal w3 intake, and that improving one's w3 intake is particularly important in the intervals between weight loss diets. However the current national trend to severely reduce dietary fat tends may have unanticipated negative effects on people with a weight problem if it leads them to avoid eating specific foods rich in w3 fats such as cold water fish, flax, almond and walnuts.
While the short term health effects of this issue for any one individual are likely to be minor, the epidemiological implications are enormous in a country in which a third of the adults are obese and half of them diet at least once per year. Because of the virtual absence of negative effects of moderate doses of w3 fatty acids in the human diet, plus the availability of foods with fats containing 30-55% w3 fatty acids, it is reasonable to advise people struggling with their weight to purposely incorporate 2-3 grams per day of this essential nutrient in their daily diets. The "price" is 4-10 grams of dietary fat intake, while the benefits potentially include reduced coronary risk, cancer, and possibly inflammatory diseases.
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