• Scientific evidence to date does not support the notion that eating a diverse diet is healthy or promotes a healthy weight.
• Some studies suggest that a diverse diet may increase food consumption and the prevalence of obesity.

Those surprising statements come from no less than the American Heart Association, which recently issued an advisory saying that diets that include a wide variety of foods may not be such a great idea after all.

The AHA notes these findings contradict the advice that “‘Eating a variety of foods’ has been a public health recommendation in the United States and worldwide for decades.” People were encouraged to consume a variety of foods—such as different colored vegetables and fruits—because it was believed this was a good way to ensure adequate intake of a range of vitamins and minerals. People were encouraged to “eat a rainbow,” with the guiding principle that even within the same foods, different colors indicate the presence of different nutrients, as in the case of purple, orange, or white cauliflower, and yellow, orange, and purple carrots. 

The problem is, where diet is concerned, “diversity” is a vague term. This important pitfall was articulated by Dr. Goutham Rao, co-author of the AHA advisory and chair of the department of family medicine and community health at University Hospitals of Cleveland and Case Western Reserve University: “What does dietary diversity actually mean? It is not clearly and consistently defined across the board, and there is no useful measure of it.”

The same could be said about “moderation.” We’re often told to eat certain foods “in moderation,” but what is moderation, exactly? Should people “moderate” their intake of broccoli to the same extent they “moderate” their intake of potato chips? Is “moderation” consuming something three times a week? Three times a month? Three times a year? What’s a “moderate” intake of starch? One slice of bread? A gigantic New York City bagel? Five saltine crackers? A bottomless bowl of spaghetti? A “diverse” diet in Japan might look very different from one in Greece, or one in Finland.

Based on 20 years of experience in the obesity field, Dr. Rao noted, “People who have a regimented lifestyle and diet tend to be thinner and healthier than people with a wide variety of consumption.” Dr. Dariush Mozaffarian, advisory co-author and dean of Tufts University’s Friedman School of Nutrition Science and Policy concurred: “When we conducted a comprehensive literature search, none of the studies convincingly showed that diverse diets lead to better health outcomes. In fact, studies show that the more diverse a diet is, the worse it is and more weight people gain.”

That’s not to say that a diverse diet is, by definition, less nutritious and more overweight-inducing than a more limited diet. It depends on the kinds of foods that are included, and in what amounts. A “diverse” diet can include a wide variety of animal proteins and non-starchy vegetables while steering clear of refined carbs and vegetable oils. A “diverse” vegetarian diet excludes animal foods but can include a range of nutrient-dense plant foods while also excluding candy bars and cupcakes. The point is, as across-the-board, population-level advice, encouraging people to consume a diverse diet seems to backfire in many cases.     

Encouraging consumption of a wide variety of food, albeit well-intended, may lead to people feeling overwhelmed by choice. Some chain restaurants offer menus 10 pages long. It’s nearly impossible to make a decision! Sticking to a diet with certain parameters—be it Paleo, vegetarian, low fat, keto, or something else—may make it easier for people to choose, and while all of these plans can definitely include a variety of foods, they all exclude something, which right off the bat, makes them at least slightly less diverse than an “anything goes” approach to diet.

Encouraging dietary diversity can result in people getting out of food ruts, and possibly getting more micronutrients, depending on the foods they choose. But the “everything in moderation” and “eat a wide variety of foods” mantras can be problematic for others, particularly those with food addictions or binge tendencies. These individuals may do much better with a more limited diet, and perhaps even a diet that’s relatively bland. That is, a diet limited in or completely free of “hyperpalatable” foods—foods scientifically engineered to be addictive. (Nacho-flavored tortilla chips come to mind, if you get the drift without a brand name!)

Some people find it much easier to completely abstain from their “trigger foods” than it is to attempt to moderate intake to a reasonable level. Gretchen Rubin’s book The Four Tendencies covers this concept nicely (and it was initially introduced in Better Than Before). There’s no right or wrong way; it depends on how a person is wired. Some people really can have just a handful of nuts, or an ounce of chips, and then put the bag back in the cupboard, completely forgotten about. Many others haven’t mastered this Jedi mind trick and are better off abstaining completely, rather than trying to put the brakes on the appetite equivalent of an out-of-control freight train.

Bottom line: patients should identify and follow the diet that gets them the best results and that they can stick to for the long term. If that’s a diet with specific rules that excludes certain foods so that it ends up being less diverse than some other approach, that’s not automatically a bad thing, and it might even be just what they need.

By Amy Berger, MS, CNS