If one gram of fat contains 9 calories, and there are about 454 grams in a pound, how come 1 pound of fat is commonly equated to be about 3,500 calories instead of about 4,000 calories?
In: 10
Most of this comes down to rounding numbers for presentation purposes.
If I told you that you could lose 1 pound a week by cutting out 3500 calories from your diet, you can divide that 3500 by 7 and see it’s 500 per day.
In reality, a lot of calorie stuff is approximate, especially when dealing with cooking raw ingredients. Having exact numbers for calories to fat isn’t going to be too helpful because the natural error in real world stuff is far greater than rounding it for the sake of the reader.
1 pound of pure oil would be close to your approximation, but human fat tissue (the thing usually being talked about with ‘1 pound of fat’ statements) involves much more than pure oil. There’s water being held in there and any connecting tissue that keeps it in place. Plus there’s all the other things involved with metabolism that make the ‘pure’ conversion less useful; a healthy person’s weight can fluctuate by multiple pounds depending on hydration levels alone. So diets that are translating a weight goal to a diet goal, the ‘3500’ number works well enough, but nobody is measuring the exact calorie change to exact weight change with reliable results anyway.
In fact that 9 cal / g is a big rounding, if you google 100g, you get 841 cal, which is 8,41 cal/g. With that number you get 3800 cal/pound (much closer to 3500).
It is known that these numbers are often rounded to an approximation for easier to remember or because anyways there can be some variance between fat and fat.
You’re right that if you do the math, 1 gram of fat (which contains about 9 calories) times 454 grams in a pound would give you about 4,086 calories in a pound of fat.
However, when we’re talking about body weight and losing or gaining fat, we’re not talking about pure fat. Body fat is not 100% pure fat but also contains some amount of water and proteins. The fat in our bodies isn’t like the cooking oil in your kitchen or the butter on your toast – it’s a bit more complex.
Researchers have found that each pound of body fat is more like 87% fat. If you do the calculation with that in mind, you’ll find that each pound of body fat contributes about 3,500 calories (0.87 * 4,086 calories ≈ 3,555 calories, which is often rounded to 3,500 for simplicity).
So, when you hear that you need to burn about 3,500 calories to lose a pound, it’s because you’re not just losing pure fat, but also some water and proteins along with it.
I’m pretty sure that these are different definitions of fat. Because 1kg of lard contains 8977 kcals, which when rounded to the closest number comes to 9 kcal per gram. Ie, a purified fat product that contains exclusively fatty acids (ie, pure fat)
However, when we’re talking about “3500 calories per pound” we’re generally talking about bodyfat. Fat tissue. And that’s not pure fat but instead a clump of fat cells that consist of mostly fat.
Ah, so my love handles are more than just pure oil? I guess that explains why they won’t fry up nicely.
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