Pureed Vegetables: A Dietary Nudge That Works

A fad in public health circles is to use “nudges” to guide people into sub-consciously making better decisions for themselves.

The idea is based on two aspects of human psychology:

1. People are cognitive misers.
2. How we frame our choices has a large impact on the decisions we make.

So theoretically subtle changes to people’s decision frameworks might have large impacts on our outcomes….without us even knowing about it.

These forces are at work all around us, but the idea behind “nudging” (the term was made popular by this book) is to channel them for good.

At least that’s how the story goes.

There are lots of examples when nudges work surprisingly well. For instance, 401(k) administrators have figured out they can put human laziness to good use by making 401(k) participation the default option. When this happens, participation rates are usually about 80%,  which is pretty darn high. The people who were too lazy or short-sighted to take the time to think about their retirement and set-up a plan are also too lazy to change anything once it’s done for them.

In the diet arena, nudges have taken various forms: listing calories next to menu items, putting the salad bar in front of the dessert tray in the cafeteria, placing red blinking lights over naughty foods and green lights above over the nice ones, and various other examples.

To well-intentioned nudgers these interventions sound great, but so far they’ve all been abysmal failures.

Like every single one.

Over the short-run there’s some effect, but over the long run people are surprisingly resilient at finding ways to eat the things they like. No matter what. Give us smaller portion sizes? Hey, no big deal! We’ll just buy more plates.

List the 500 calories we’ll be ingesting by gulping down an extra large Caramel latte frapuccino? We might get a little bit of a sticker shock, but eventually we’ll just tune it out and drink the damn thing anyway.

Like clockwork.

The situation seems intractable…….perhaps.

Turns out a paper was recently published that shed light on a quasi-nudge that actually worked.

It was targeted towards children, and they pureed vegetables and secretly put them into their food. The effects on their diet were very positive:

The daily vegetable intake increased significantly by 52 g (50%) in the 85% ED condition and by 73 g (73%) in the 75% ED condition compared with that in the standard condition (both P < 0.0001). The consumption of more vegetables in entrées did not affect the consumption of the vegetable side dishes. Children ate similar weights of food across conditions; thus, the daily energy intake decreased by 142 kcal (12%) from the 100% to 75% ED conditions (P < 0.05). Children rated their liking of manipulated foods similarly across ED amounts.

The researchers gave different groups of meals that were injected with vegetable puree of varying concentrations and studied how they changed their diet, if at all.

Here are the key facts:

1. The amount of food the kids ate was insensitive to the amount of vegetable puree in their meal.
2. The vegetable puree had no effect on how they ate other side dishes (like their other vegetables).
3. Kids reported no decreased satisfaction with vegetable puree injected meals.
4. Average caloric intake per meal went down 142 calores.

If you add that up, it’s a pretty big deal. It’s a painless way to make people eat healthy that actually works.

Mothers, cafeteria planners, and public health officials – take notice.