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LETTER TO THE EDITOR |
Friedman School of Nutrition Science and Policy
Tufts University
Boston, MA 02111
E-mail: caleb.kelly{at}tufts.edu
Dear Sir:
Studies in rodents have shown a marked increase in lifespan and disease resistance in animals subjected to intermittent fasting (1, 2). The suggestion that humans may respond similarly to a reduced meal frequency raises several important questions. Is reduced meal frequency feasible in humans? Does reduced meal frequency confer health benefits independent of calorie restriction? Are there alternative approaches by which to study the relation between meal frequency and longevity? The recent article in the Journal by Stote et al (3) provides insight into this inadequately studied aspect of human nutrition (4). With respect to the first question, the trial by Stote et al (3) and that by Heilbronn et al (5) showed that compliance with once-a-day and alternate-day feeding is feasible for humans participating in controlled trials. However, greater subjective ratings of hunger indicate that compliance is unlikely in free-living persons. In addition, restricting consumption to once a day may compromise diet quality. In the trial by Stote et al, subjects consuming one meal a day "reported extreme fullness after the meal and had difficulty finishing their food in the allotted time." This occurred despite the selection of energy-dense foods and a fiber intake of only 7.4 g/1000 kcal, which is below the current adequate intake of 14 g/1000 kcal (6). Foods with low energy density, such as fresh fruit, vegetables, water-rich whole grains, and legumes, are associated with high diet quality (7). Adherence to a diet restricted to one meal a day would preclude frequent selection of such foods because of their bulk. A direct comparison between the study by Stote et al and those studies performed in animals is complicated by methodologic differences. However, the absence of overlap in measured biomarkers suggests that reduced meal frequency without calorie restriction in humans is unlikely to achieve the extension in lifespan seen in animal models.
As discussed by Stote et al, Muslims who fast during Ramadan exhibit physiologic adaptations to the consumption of 2 meals/d. A different 2 meals/d pattern is followed by some Seventh-day Adventists (8). The proportion of Seventh-day Adventists who adhere to a 2 meals/d pattern is lower than that of Muslims during Ramadan. Yet, among Seventh-day Adventists, the 2 meals/d pattern typically is chronic, and sometimes lifelong, which would allow sufficient time to achieve stable changes in physiology. The timing of meals represents another distinction between these 2 religious groups. During Ramadan, Muslims eat before dawn and after dusk. Seventh-day Adventists following a 2 meals/d plan typically consume their final meal in the afternoon. This pattern results in a longer period between dinner and breakfast, which may be biologically important (9). Seventh-day Adventists had a greater life expectancy than did other white Californians (10), which has been attributed to low smoking rates, their emphasis on the consumption of a plant-based diet, and several other lifestyle factors. However, the relation between reduced meal frequency and longevity among Seventh-day Adventists has never been studied. Prospective or cross-sectional studies of Seventh-day Adventists present a valuable opportunity to clarify the relation between meal frequency and longevity in humans.
ACKNOWLEDGMENTS
The author had no personal or financial conflict of interest.
REFERENCES
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