Calorie counting has been a staple of weight loss programs for over a century.

It’s still a popular way to approach weight loss, whether it’s staying below a certain calorie limit on fasting days or using an app to calculate “calories in” by in relation to “calories out”.

But many leading experts are now calling for that to change.

They say calorie counting is based on flawed and outdated science.

And they say our obsession with calories actually served to make us fat.

calorie confusion

The calorie’s history is “complicated,” says University of South Carolina historian Allison Marsh.

“The term calorie is emerging on different continents at different times with different meanings,” she told ABC RN’s Rear Vision.

The calorie began life as a unit of stored heat.

French physicist Nicolas Clément used the term in the 1820s when lecturing on the efficiency of steam engines.

He defined the calorie as the heat required to raise the temperature of one kilogram of water by one degree Celsius.

This was not the only definition, however, with others defining a calorie as the heat required to warm a single gram of water one degree Celsius – a 1,000th unit the size of Clement’s.

In 1879, the French chemist and politician Marcellin Berthelot distinguished the two units by designating the smaller as a calorie, with a lowercase c, and the larger as a capitalized calorie.

Adding to this confusion, the calorie is not the standard unit of energy in the International System of Units – it is the joule (one kilojoule equals 1000 joules).

Potential energy

Part of the reason for the calorie’s continued use, particularly in the United States, was due to an 1887 article by chemist Wilbur Atwater, titled The Potential Energy of Food, published in the popular monthly magazine Century.

Rather than trying to measure the fuel energy of steam engines, Atwater was trying to measure the metabolic rate of the human body.

“He was really interested in how the body processed energy,” says Dr. Marsh.

He started measuring the potential energy of different types of food.

But, unlike some previous efforts to do this, he didn’t measure the food just once.

Atwater looked at how much of the food we eat is actually absorbed by the body. He understood what Giles Yeo, an obesity researcher at the University of Cambridge, calls the “sweet corn scenario”.

“You eat corn on the cob, then the next day you look in the toilet and you clearly haven’t absorbed all the sweet corn,” says Dr. Yeo.

Atwater therefore measured the calories of many different foods. Then he gave these foods to human subjects, waited for them to digest the food, and measured their feces.

He subtracted the poo calories from the food calories so to calculate the total number of calories consumed.

He used these calculations to come up with a system for determining the calorie content of foods, such as nine calories per gram of fat and four calories for each gram of carbohydrate or protein.

“These numbers, these Atwater factors as they’re still called, are the basis of all the calorie counts we see on every packet of food around the world today,” says Dr. Yeo.

calorie counting

Obesity was not a pressing public health issue in the 19th century, with experts becoming more interested in tackling malnutrition.

But in the 20th century, weight loss became a priority, especially for women looking for the “ideal” body shapes featured in magazines and on the big screen.

In 1918, Dr. Lulu Hunt Peters published her bestselling Diet and Health: With Key to the Calories.

The book was based on his column in a syndicated newspaper in which she documented her weight loss process.

She calculated the calorie content of various foods in her diet and counted the number of calories she ate.

“She started trying to cut calories to lose weight and it was successful,” says Dr Yeo.

Dr. Yeo says Peters’ book has “weaponized” the calorie.

“She was the mother of calorie and calorie counting in weight loss.”

The halo effect

In the years following World War II, American public health authorities became increasingly concerned about the rising rate of heart disease, associated with weight gain.

In an attempt to slim down the population, the calorie concept has become popular. “It was something people thought they could control,” says London-based freelance journalist Peter Wilson. who wrote death of the calorie in The Economist magazine of 1843.

Fat became the focus of government policy because a gram of fat contained more calories than a gram of carbohydrate or protein, he says.

Politics also came into play.

“The sugar lobby outsmarted, lobbied and paid more than the big lobby, and [they] succeeded in blaming fat for being the cause of obesity, diabetes and the increased incidence of heart attacks,” he says.

The food industry loved it, Wilson says, because it could make highly processed foods that claimed to be healthy because they were low in fat.

The products were cost effective, Wilson says, and had a long shelf life because fat was replaced with sugar, starch and salt.

An example of such a product, according to University of Sydney historian Chin Jou, was SnackWell’s, a heavily advertised brand of low-fat biscuits.

“The idea was that Americans could have it both ways — that they could enjoy delicious foods and that those foods could be low in fat,” Dr. Jou says.

The cookies were delicious, she says, because they were “loaded with sugar.” However, since they were low in fat, they contained fewer calories than other cookies.

Worse still, these foods encouraged overeating.

“The problem is that these products had what is academically called the ‘halo effect,'” she says.

“These foods are considered okay to eat – the opposite of sin – and because of this, people might abuse them.”

Rather than having one or two cookies, Dr. Jou says, people would eat the whole packet and still be hungry.

“These foods would be high glycemic index (GI) foods, in which people’s blood sugar levels would spike and they would be hungry soon after.”

Calories don’t add up

It’s not just our diet that has contributed to rising obesity rates.

People are doing less physical labor these days as our jobs are becoming more sedentary and our homes are filled with labor-saving devices.

“It’s a mix between the environment, the food environment and, really, our way of life,” says Dr Yeo.

Diet still plays an important role, but Dr. Yeo says the problem with focusing on calories is that not all calories are created equal.

While our bodies have to work for the calories in unprocessed foods, he says, fast foods and convenience foods are “much more available in calories.”

“Even if we ate the exact same 400 calories, we would take in a lot more calories than if we ate steak or sweet corn,” he says.

That’s one reason, he says, that you can’t decide which food is healthier just by comparing their calorie counts.

“We now equate calories with health when that’s not what the calorie was designed for,” he says.

Another reason, he says, is that Atwater’s system typically produces the wrong calorie count.

The system only gives the calorie content of protein, carbohydrates and fat, he says.

The system is also unreliable, he says, with calorie counts for meals being around 10% lower on average.

“The problem is that 10% adds up pretty quickly. 10% is 200 calories of a 2,000 calorie meal, 10% of 20,000 calories is 2,000 calories.”

While Atwater’s system is appealing in its simplicity, Yeo says, that doesn’t change the fact that it’s inaccurate.

“It may be difficult, but I think we should be able to do better because it’s incorrect,” he said.

“I hate things that are wrong. We should try to fix them, because they are bad.”