להמליץ לאנשים לאכול תפריט שמכיל "כל דבר במידה" – אינו מועיל, וכנראה אפילו מזיק. לפחות כך על פי המחקר האמרקאי הזה:
"Everything in moderation" is a poor principle to base one's diet on
Dietary diversity, in the sense of eating less of similar foods, is an old and popular, but apparently not very effective principle, as it may be linked to lower diet quality and worse metabolic health. These are the findings of a US study published in "PLOS ONE".
Researchers at The University of Texas Health Science Center at Houston and Tufts University in Boston analysed data from 6,814 participants in the Multi-Ethnic Study of Atherosclerosis, evaluating diet diversity through different measures. These included the number of different foods eaten in a week, evenness (distribution of calories across different foods), and dissimilarity (differences in attributes such as fiber, sodium or trans-fat content). The team evaluated how diet diversity was associated with change in waist circumference five years after the beginning of the study and with onset of type 2 diabetes 10 years later.
No associations were seen with either increase in waist circumference or incidence of diabetes. In other words, more diversity in the diet was not linked to better outcomes. Participants who had the greatest food dissimilarity actually experienced more central weight gain, with a 120 per cent greater increase in waist circumference than participants with the lowest food dissimilarity.
Analysing the food quality, the researchers found that participants with greater diversity in their diets, as measured by dissimilarity, actually had worse diet quality. "They were eating less healthy foods, such as fruits and vegetables, and more unhealthy foods, such as processed meats, desserts and soda," said study author Marcia C. de Oliveira Otto. "This may help explain the relationship between greater food dissimilarity and increased waist circumference."
"Americans with the healthiest diets actually eat a relatively small range of healthy foods," said senior author Dariush Mozaffarian. "These results suggest that in modern diets, eating 'everything in moderation' is actually worse than eating a smaller number of healthy foods."