How can certain foods have so many more calories while being so much less material? For example 3 Oreos have more calories than a whole can of tuna.

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How can certain foods have so many more calories while being so much less material? For example 3 Oreos have more calories than a whole can of tuna.

In: Chemistry

Usually foods with high calories for their size are laden with sugar. Carbohydrates provide a lot of calories for not being very heavy.

Tuna is mostly water, like we are. It has a lot of protein. It’s calories come mostly from that protein. Oreos are mostly carbohydrate and fat. They have very little water.

Oreos are basically sugar and fat.

Sugar is 4 calories per gram, protein is 4 calories per gram, fat is 9 calories per gram.

100g of Oreos contains 69 grams of carbohydrate, 20 grams of fat and 5 grams of protein. Which means 100g of Oreo contains around 500 calories.

Tuna is mostly water.

100g of tuna contains 0 grams of carbohydrates, 1 gram of fat and 20 grams of protein. For a total of about 90 calories.

Size of food isn’t important, composition is.

This is exactly why so many people over eat.

It also might be helpful to know that Calories are calculated by how much energy the food puts off when burned. This is why water has essentially zero calories and if we could consume gasoline, it would provide a ton of calories.

A calorie is a unit of heat measurement, like a joule. You can actually measure things like gasoline in terms of the number of calories they produce when burned. But usually we use calories to talk about the energy we derive from food.

When we digest food, we break down the molecules and release the energy from the chemical bonds. This chemical reaction is called “burning” calories because the reaction produces heat and waste product (CO2). This is not fundamentally different from any other chemical reaction used to produce heat.

Carbohydrates are energy dense molecules. For example, Glucose’s chemical formula is C6H12O6. Any time you see a molecule that includes lots of Carbon, Hydrogen, and Oxygen, you are probably looking at something that will burn pretty good. These atoms form dense molecular bonds that release a lot of energy when they decompose. Sugar will, in fact, burn violently when you mix it with heated potassium chlorate. (Do not try this at home.)

Sweets contain lots of sugar, which means they have lots of energy-dense molecules ready to light up. Vegetables and other healthy foods contain fewer sugars and more filler material like water and indigestible plant fiber. This means that they have less energy (calories) per gram of material.