The mantra to “eat a diverse diet” may have been good years ago, but recent studies have shown that today a more diverse diet is likely to include many unhealthy foods and is not associated with a better body weight.
Thus, advice for diet diversity needs to be updated to instead emphasize “an adequate intake of healthy food,” according a scientific advisory about diet diversity for obesity prevention in adults, which was issued by the American Heart Association (AHA) and published online August 9 in Circulation.
“Current data do not support greater dietary diversity as an effective strategy to promote healthy eating patterns and healthy body weight,” the statement concludes.
Instead, “it is appropriate to promote a healthy eating pattern that emphasizes adequate intake of plant foods, protein sources, low-fat dairy products, vegetable oils, and nuts and limits consumption of sweets, sugar-sweetened beverages, and red meats.”
This review could help inform recommendations about diet when the 2015-2020 Dietary Guidelines for Americans is updated, the statement’s writing chair, Marcia C de Oliveira Otto, PhD, MS, from the University of Texas Health Science Center at Houston, told theheart.org | Medscape Cardiology.
Emphasizing diet diversity appears to be “leading people to eat too much unhealthy food — a lot of sodium, trans fat, processed food, and so on,” she said.
Unfortunately, research into diet diversity “typically does not take into account the quality of the food,” Frank B. Hu, MD, PhD, professor and chair of the Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, who was not involved with this advisory statement, told theheart.org | Medscape Cardiology.
“In the old days,” said Hu, who served on the advisory committee for the 2015-2020 Dietary Guidelines, “you needed to get sufficient amounts of macronutrients and micronutrients by consuming a wide range of food, but today, nutrient deficiency is much less of an issue and obesity has become a much more important public health problem.”
So “Eat a variety of foods” is not that meaningful anymore in a setting where there is an “overabundance of foods, including so many different kinds of packaged and processed and commercial food products,” he said.
More Food Variety, Less Excess Weight?
For this review, the writing committee identified studies about diet diversity that were published between 2000 and 2017, to see whether a greater food diversity was associated with less obesity.
They found few studies, which were very heterogeneous and used three different ways to define diet diversity.
Most studies measured the “count” or the number of different foods/food groups consumed, usually within a week (which could be up to 5 or 24, in different studies).
The other measures were “evenness,” or whether most calories were coming from a few food types or many foods, and “dissimilarity,” or whether a person’s calories mostly came from similar or dissimilar foods.
This “limited evidence” did not show that diet diversity promoted an optimal diet or healthy weight, but rather, it suggested that people with a more varied diet consumed more calories, had poor eating patterns, and gained weight.
A few studies suggested that when people have a wider variety of foods to choose from in a meal, they tend to overeat.
However, the studies were manly observational and had various limitations — notably that they did not assess nutritional quality along with food diversity — so more research is needed, Otto said.
More studies are needed to see whether eating a variety of healthy foods (eg, fruits and vegetables) provides more benefits, as are “robust, well-designed prospective studies” to assess the link between “dietary diversity and clinical, metabolic, and cardiovascular outcomes,” Otto and colleagues urge.
According to Hu, “the traditional concept of diet diversity…is basically outdated.”
“To move this field forward,” he said, “we cannot just count the number of foods anymore; we need to incorporate both the quality and the quantity into the [healthy-diet] index.”
One way to do this would be to “give positive points to the diversity of healthy foods,” Hu suggested.
“If you eat more fruits and vegetables…or perhaps different types of whole grains and legumes, then you get more positive points,” with more processed meats, such as sausages and bacon, for example, awarded negative points.
Otto and Hu have disclosed no relevant financial relationships.
Circulation. Published August 9, 2018. Abstract