Why the 2,000 Calories-Per-Day Recommendation Is Completely Meaningless

Remember that day in high school chemistry class when you donned safety goggles, stabbed a peanut with a sewing needle, and set that peanut on fire? And the experiment's point was to show a peanut had enough energy to raise 1g of water one degree Celsius at sea level, which equalled one calorie? And you thought, "This sounds totally arbitrary, and also, I bet this needle would look cool in my cartilage piercing"? That happened to everyone, right?

Well, you were correct. Sewing-needle piercings are cool and calories are meaningless -- specifically, the 2,000 calories-per-day baseline you've seen on every nutrition label the majority of your life. Meaningless is putting it politely: "A gross over-simplification and extremely inaccurate 'guesstimate'" is how Dr. Brian Quebbemann, a Fellow of the American Society for Metabolic and Bariatric Surgery, describes the FDA's 2,000 calories-per-day recommendation. Let's delve into why this guideline, like so many systems we use to impose structure on our paltry lives, is bunk.

Nutrition labels as you know them aren't all that old

If you were alive and cognizant prior to the 1990s, you probably remember that nutrition labels on foods looked different; they didn't have percent-daily values based on a 2,000-calorie diet. That's because the Nutrition Labeling and Education Act was signed into law in 1990, requiring manufacturers to be more transparent about their dietary claims -- for example, if a yogurt's going to be touted as high-protein, consumers would know exactly how much protein is in a serving.

These new labels also made it easier for people to track their daily fat and salt intake. "Because the allowable [saturated fat and sodium] limits would vary according to the number of calories consumed, the FDA needed benchmarks for average calorie consumption," writes Marion Nestle in Why Calories Count: From Science to Politics.

Enter 2,000.

Why land on 2,000 calories?

Doctors didn't just pull it out of thin air, did they? Of course not! They used (finger quotes) SCIENCE. Although a male college athlete's caloric needs vastly differ from those of a postmenopausal woman, for example, there's no way all those different benchmarks would fit on the side of a cereal box. So the FDA decided to go for a middle-ground approach. "The FDA wanted a single number so their recommendations would be simple to follow, and also they did not want to encourage overeating," Dr. Quebbemann says.

The FDA arrived at 2,000 using surveys of how much food people consumed per day, Dr. Quebbemann says. This ranged anywhere from 1,600 calories to 3,000 calories. It averaged the data and came up with a single number, which was… not 2,000. The FDA initially proposed setting the daily value at 2,350 calories, which gives you at least an extra snack, but decided on lowering the amount to 2,000 after asking for public comments and deciding that anything above 2,000 might encourage people to overeat. Which probably isn't a bad assumption, knowing Americans, even though going down to 2,000 is a significant reduction.

"It's a bit like measuring the weight of everyone in America, determining the healthy weight of all adults in the United States averaged over the entire population and across the sexes and ethnic groups, and then saying that a healthy person in the USA 'should weigh' the average weight," Dr. Quebbemann says. Which sounds like a terrible idea, but an interesting premise for the next dystopian YA franchise.

So how many calories should you actually eat?

First, the bad news: it's really hard to judge an individual's daily caloric needs. There are three reasons for that, Dr. Quebbemann says: first, it's impossible to accurately estimate the volume of food without weighing everything; second, most food is largely composed of water, which has no calories; third, most people lie to themselves about how much they eat and fudge the data.

The good news? You don't need to know how many calories you're eating, as long as you follow one simple guideline: "If you're getting fatter, you're eating more calories than you need," Dr. Quebbemann says. Though that's probably not what you want to read on the side of a cereal box.

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Missy Wilkinson doesn't trust the Weight Watchers "points" system, but her mom is really into it. Follow her on Twitter @missy_wilkinson.