The system for counting calories comes from chemist Wilbur Atwater. To find out how much energy we get from eating, he measured the nutritional value in food and subtracted the amount of energy left in people's bodily excretion.
His research resulted in the 4-9-4 rule: Each gram of protein, fat, and carbohydrate provides 4, 9, 4 calories of energy, respectively.

Counting calories in food

Nutritionists are calling for calorie intake and nutrition information to be reviewed.
<ul>
<li>They say the present system does not differentiate between raw and cooked food. Processed food is easier to absorb, so it provides more calories.</li>
<li>USCA researchers found that pistachios' caloric value had been overstated by 5 percent on the nutrition label. Almonds were overstated by 32 percent.</li>
</ul>

Reappraisal of calorie intake

Nutritionists warn of one big caveat with the numbers on the packaging.<figure><img alt="A bag of chocolate chip cookies holding up a sign that says &quot;nutrition facts, one cookie, 320 calories&quot;" src="https://www.popsci.com/resizer/BB0Q6jnUEJiPlJtBQ4w6_6CbLSA=/769x577/cloudfront-us-east-1.images.arcpublishing.com/bonnier/YPWWQ6MC2DM4BOWBYJEC546BUA.jpg"><figcaption dir="auto">Calorie counts are built on decades-old science. Jason Schneider</figcaption></figure>This post has been updated. It was originally published on 1/12/2016.America’s century-old system for <a href="https://www.popsci.com/counting-calories-effective/" dir="ltr">counting calories in food</a> comes from chemist Wilbur Atwater. In 1887, he began to research the energy we get from eating by measuring the nutritional value in different meals and subtracting the amount of energy left in people’s bodily excretions.Atwater’s research has since been boiled down to the 4-9-4 rule: Each gram of protein, fat, and carbohydrate provides, respectively, 4, 9, and 4 calories of energy. The United States Department of Agriculture (USDA) has used these figures for decades, tweaking them only to account for different qualities—such as the digestibility—of <a href="https://www.popsci.com/negative-calorie-foods/" dir="ltr">specific foodstuffs</a>.But in the past decade, nutritionists have clamored for a reappraisal of calorie intake and nutrition information. For one thing, they say the present system ignores the difference between raw and cooked food. Harvard University researchers assert, based on mouse studies, that processed food is easier for the body to absorb, so it provides more calories. That goes for baked or blended food. Even a handful of chopped peanuts gives you more energy than whole ones.In 2011, USDA researchers, with a grant from the nut industry, reported that the caloric value of pistachios had been overstated by 5 percent on the nutrition label. In 2012, they found almonds were overstated by 32 percent, or 40 calories per serving. So you might not want to take labels at face value.This article was originally published in the <a href="http://www.popsci.com/future-car-and-more-from-november-2015" dir="ltr">November 2015 issue</a> of Popular Science

If you're aiming for a recommended daily average of calorie intake and using nutrition labels to track your numbers, you might want to rethink your diet strategy.

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Nutritionists warn of one big caveat with the numbers on the packaging.

This post has been updated. It was originally published on 1/12/2016.

America’s century-old system for <a href="https://www.popsci.com/counting-calories-effective/">counting calories in food </a>comes from chemist Wilbur Atwater. In 1887, he began to research the energy we get from eating by measuring the nutritional value in different meals and subtracting the amount of energy left in people’s bodily excretions.

Atwater’s research has since been boiled down to the 4-9-4 rule: Each gram of protein, fat, and carbohydrate provides, respectively, 4, 9, and 4 calories of energy. The United States Department of Agriculture (USDA) has used these figures for decades, tweaking them only to account for different qualities—such as the digestibility—of <a href="https://www.popsci.com/negative-calorie-foods/">specific foodstuffs </a>.

But in the past decade, nutritionists have clamored for a reappraisal of calorie intake and nutrition information. For one thing, they say the present system ignores the difference between raw and cooked food. Harvard University researchers assert, based on mouse studies, that processed food is easier for the body to absorb, so it provides more calories. That goes for baked or blended food. Even a handful of chopped peanuts gives you more energy than whole ones.

In 2011, USDA researchers, with a grant from the nut industry, reported that the caloric value of pistachios had been overstated by 5 percent on the nutrition label. In 2012, they found almonds were overstated by 32 percent, or 40 calories per serving. So you might not want to take labels at face value.

This article was originally published in the <a href="http://www.popsci.com/future-car-and-more-from-november-2015">November 2015 issue </a>of Popular Science

Why you can’t trust the calorie count on food labels

Counting calories in food

Reappraisal of calorie intake

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