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Everything in moderation is a piece of advice that makes intuitive sense. After all, research has shown that the strictest diet is rarely the best one — place something off-limits, and you’re more likely to crave it even more. Allow yourself a cheat day every so often, on the other hand, and you may be able to stick more easily to a healthy-eating plan. Having dessert once in a while won’t kill you. Neither will the occasional cheeseburger. Just, you know, in moderate amounts.

But examined more closely, just telling someone to eat unhealthy things in moderation is a bit like asking them to re-create a recipe that calls for a pinch of one ingredient and a dash of another. Your idea of a pinch and a dash, in all likelihood, is going to be different from mine. Maybe it even changes each time you cook, or fluctuates depending on what you’re making.

In other words, it’s an instruction so vague as to be fundamentally unhelpful. And in the absence of any standard measure, we’re each left to our own devices to figure out what moderation actually means. Which isn’t really a great strategy, as far as health strategies go: According to a new study in the journal Appetite, we tend to define moderation as whatever we’re already doing — or, in some cases, we push the threshold to just above our normal habits, so that moderation comes to mean eating a bit more than we have been.

For the first part of the study, the authors presented volunteers with a plate of 24 chocolate-chip cookies and asked them to define three things: how many cookies they thought a person should eat at a time (on average, 2.25 cookies), how many could be considered a “moderate” amount (slightly more than three cookies), and how many would be considered an “indulgent” amount (just under six cookies). In the second part, a separate group of volunteers viewed photos of gummy candies and then answered a similar set of questions: how many candies a person should eat at a time (around eight), and what would constitute moderate (around 11) and reasonable (just over 14) amounts to eat.

Put another way, the subjects were kind of all over the place, defining moderation in a way that didn’t really seem to follow any consistent logic. It was something less than indulgence, but also, oddly, more than a person should be expected to consume at one time — suggesting, the researchers wrote, that people don’t really consider it to be a limiting concept.

The final portion of the study, which asked people to describe their habits around certain unhealthy foods (pizza, ice cream, fast-food meals) supported this idea: When asked to define moderation for each type of food, they tended to pin the definition somewhere north of their own consumption level. “The more participants consumed of a particular food or beverage category, the greater the consumption of that product they defined as moderate,” the study authors wrote. “To the extent that participants consumed relatively little of an item, they also suggested that moderate consumption would be indicated by relatively little consumption of that item.”

And when the participants were also asked to rate how moderate their eating habits were for each food type, things got a little more nonsensical: Their answers were totally unrelated to the definitions they’d just given. A person who said that pizza once a week was moderate, for example, might still report that their four-times-a-week habit was moderate, too. “The extent to which people believed they consumed foods in moderation was unrelated to how much of that food or drink they reported consuming,” the authors wrote. “Furthermore, participants’ ratings of their consumption as moderate for a given food item were unrelated to their definitions of moderate consumption of that item.”

In a way, these mental gymnastics fit in nicely with the rest of our collective psychological quirks around food — in general, we’re pretty bad at guessing the calorie content of our meals, and even how much we’ve just eaten. And past research has shown that we often twist beliefs to cast ourselves in the best possible light; it seems fitting, then, that what we call moderation is based in large part on what we consume, rather than the other way around.

Besides, moderation is a relative term, not an absolute one: moderate in relation to what? Granted, there are some ways to treat it as a useful, quantifiable concept — like in the Weight Watchers program, which assigns points to each and every food to help people keep careful track of what and how much they’re eating. In that case, moderation is a clear line that can be reached or surpassed, and people can use it to guide their choices accordingly. Without that line, though, the definition can be molded any which way — a fact that gives the concept infinite flexibility, a dash of convenience, and just the smallest pinch of practical value.