“It’s not what you do once in a while, it’s what you do day in and day out that makes the difference.” —Jenny Craig
Have you ever eaten the same thing every day for a week straight?
To most people — foodies and nutritionists, especially — the idea probably sounds boring at best and, at worst, unhealthy.
In fact, it directly contradicts the United State Department of Agriculture’s (USDA) dietary guidelines, which suggest that we should, “Over the day, include foods from all food groups: vegetables, fruits, whole grains, low-fat dairy products and lean protein foods.”
And research supports variety in healthy food groups, showing that eating a variety of nutrient-dense foods like fruits and vegetables is associated with numerous positive health outcomes, such as increased longevity and decreased chronic disease risks.
However, new research is beginning to show some counterintuitive benefits to limited, repetitive eating, such as controlling junk-food consumption, which scientists are hopeful can help people achieve their dietary goals.
Food variety is simply a tool: The key is knowing when and how to use it.
Limit Unhealthy Options
You’ve probably at some point in your life eaten something particularly delicious (think ice cream or pizza) and exclaimed, “I could eat this every day for the rest of my life!”
Nutrition researchers at the University of Tennessee have called that bluff, designing a study of more than 200 adults split into two groups who were both placed on similar caloric diets. One group (half of the adults) were limited to eating only two items of junk food of their choosing for an 18-month period. Sure, they’d be better off skipping junk food altogether, but compared with the control group, the limited-variety group consumed less calories from junk food overall, suggesting that their boredom with their two choices led to lower consumption.
Dr. Hollie Raynor, a nutrition professor at the University of Tennessee, led the study and says their results indicate, “that limiting variety of a particular food group decreases consumption of a food group — which could help people trying to reduce intake of certain foods.”
In a review of the existing research on dietary variety, researchers suggest “a reduction in dietary variety of highly palatable, energy-dense foods may be useful in the treatment and prevention of obesity.” However, Raynor cautions that so far research hasn’t shown conclusively that limiting junk-food variety leads to weight loss, just less junk food eaten.
So limiting variety of junk food may help us eat less, which is a good first step, but is there a way to use this knowledge to help us fill up on healthier, more nutritious foods? The answer is yes, and it’s thanks in part to something called sensory-specific satiety, which is when there is a reduction in satisfaction and intake with the consumption of a certain type of food and then the return of appetite when there is exposure to a new food.
Using Variety to Your Advantage
There is research in both humans and animals that shows that the greater variety of foods you have within a meal or in your diet, the more you will eat. Dogs (or humans) offered a buffet of foods will eat more than those offered dog chow every meal — and are also more likely to be obese.
Also, a longitudinal study of more than 1,000 adults found a positive association between the variety of snacks and risk of being overweight over the course of five to nine years.
Maya Vadiveloo is a nutrition research fellow at the Harvard School of Public Health who is studying using dietary variety in a positive way — to increase consumption of healthy foods such as fruits and vegetables.
“If you look at short-term experiments, we see that someone eats consistently more of a food group — it doesn’t matter if it’s healthy or not — if they have a variety of it,” says Vadiveloo.
“If I give you as many apples as you want, over time your intake (in the same meal or day after day) will decrease because your appetite for that flavor, that texture, that particular food goes down. But once I give you a new food — say an orange — it’s not that you’re so sated that you won’t continue to eat, you were just sated from that flavor,” explains Vadiveloo.
Increased consumption of fruits, vegetables, whole grains and legumes are associated with a variety of health benefits, including decreased chronic disease risk and decreased body weight, and Vadiveloo thinks dietary interventions could take advantage of these findings about variety to increase consumption of those food groups through novelty.
Vadiveloo says she’s also working on a study to try to determine if novel ways of preparing a food can “trick” the brain out of the boredom that develops over repeated presentations of the same food.
“I’m interested in this line of research because it might help make a healthy diet pattern a little bit more enjoyable and tasty.”