---
title: 'How The Calorie Content Of Food Is Determined'
source: 'https://youtube.com/watch?v=49EaMd1fu-E'
video_id: '49EaMd1fu-E'
date: 2026-06-29
duration_sec: 185
---

# How The Calorie Content Of Food Is Determined

> Source: [How The Calorie Content Of Food Is Determined](https://youtube.com/watch?v=49EaMd1fu-E)

## Summary

The video explains how the calorie content of food is determined, starting with the definition of a calorie as a unit of energy. It covers the historical bomb calorimeter method and the modern Atwater system used by manufacturers today.

### Key Points

- **What is a calorie?** [00:15] — A calorie is the energy needed to raise one gram of water by one degree Celsius at standard atmospheric pressure. Food calories are actually kilocalories (1,000 actual calories per listed calorie).
- **Bomb calorimeter method** [00:44] — Food was burned in a sealed water-filled container; the temperature rise measured the total calories. This method overestimated ingested calories because it included indigestible components like fiber.
- **FDA and the Atwater system** [01:15] — The 1990 Nutrition Labeling and Education Act led to the Atwater system, which sums calories from nutrients using standard energy densities: 4 kcal/g for protein and carbs, 9 for fat, 7 for alcohol, 3 for organic acids.
- **Example calculation** [02:17] — A snack with 5g protein, 10g carbs, and 15g fat would be labeled as 225 calories (5×4 + 10×4 + 15×9 = 20+40+135 = 195? Wait recalc: 5×4=20, 10×4=40, 15×9=135, total 195. The transcript says 225, but that's an error? Actually transcript says 225, but we'll note the example.)

## Transcript

Hello, I'm Simon Whistler, you're watching the Today I Found Our YouTube channel, and in the video today, we're looking at how the calorie content of food is determined. First of all, let's make sure everybody here understands what a calorie is.
A calorie is just a measurement of energy. The amount of energy needed to raise one gram of water, one degree Celsius, at standard atmospheric pressure. This makes sense when talking about calories in food. Food provides energy, and our bodies need this energy to function throughout the day.
Second, it's also important to note that calories in food are actually measured in kilo calories, so 1,000 actual calories for everyone calorie listed. Manufacturers used to measure calories using a bomb calorie unit.
This process involved placing the food source in a sealed container filled with water. They would then burn the food with electrical energy. After the food completely burned up, they would measure the water temperature to see how many degrees it was raised, and thus how many
calories had been used. In 1990, under the Nutrition Labeling and Education Act of 1990, the FDA began requiring food manufacturers to label the amounts of nutrients and calories contained in their products. This act resulted in moving away from the bomb calorie
unit method for determining the number of calories in food. One reason for this was to make it easier, ran less expensive for manufacturers to meet the standard. Another was that the bomb calorie unit method measures all available calories in the product. Since most foods contain indigestible
components like fiber that pass through our system and get excreted in the form of bum brownies, this would lead to a consistent overestimation of the ingested calories using the bomb calorie unit. Instead, they used an easier method known as the at-water system.
This approach adds up the calories available through the energy containing nutrients in the food item, like protein, carbohydrates, fats, and alcohols. They use standard reference tables for common ingredients based on their energy densities. Things like four-key localities
for proteins, four for carbohydrates, three for organic acids, nine for fats, and seven for drinkable alcohols, ethanol. No wonder all that beer can give you a soft belly. It has over 1.5 calories per mass as proteins and carbohydrates. It's worth it, though.
So for a specific example, let's say that tasty snack you have before you jump on the treadmill contains 5 grams of protein, 10 grams of carbohydrates, and 15 grams of fat. The label on that package would then read 225 calories. Or technically 225,000 calories for those who can't stand over
simplification, which does result in misconceptions. So I really hope you found that video interesting. If you did, please do give us a like below and don't forget to subscribe if you haven't already. Over there on the right are a couple of other videos you will probably enjoy if you enjoyed this one.
I know if you're on a mobile device, you can't click those, you can't click the subscribe button below me so there will be links in the description below. And thanks for watching.