One Pound of Fat = ? Calories

In my training as a dietitian, I learned that to lose one pound of fat you need to create a deficit of 3,500 calories. This never really seemed to make sense to me for a number of reasons, but I couldn’t find any science disputing it until I heard a lecture from Dr. Zoe Harcombe. She asked the following seven UK organizations: the National Health Service (NHS); the National Institute for Clinical Excellence (NICE); the Department of Health; the National Obesity Forum; the Association for the Study of Obesity; the British Dietetic Association and Dieticians in Obesity Management and five of these have no idea where the calculation even comes from. The two that tried to prove it failed by a factor of about ten.

Here’s the breakdown and history of the 3,500 calories = one pound of fat myth.

-The calorie formula is based on the assertion that one pound of fat contains 3,500 calories:

-One pound equals 454 grams

-Fat has nine calories per gram

-Human fat tissue is approximately 87% lipid

-So, 454 grams of body fat tissue has about 395 grams of pure fat = 3,555 calories

-The National Obesity Forum web site states "one less 50 calorie plain biscuit per day could help you lose 5lbs (2.3kg) in a year - and one extra biscuit means you could gain that in a year!" (Ref 1)

-Evidence in obesity journals shows fat has anywhere between 8.7 (Ref 2) and 9.5 (Ref 3) calories per gram.

-So, one pound of fat could contain 2,843 and 3,752 calories.

-Given that it is currently held that one pound is 3,500 calories we could (according to this formula) inadvertently 84lbs ever year and lose 32lbs in the same year if one pound is 3,752 calories.

- This calculation is done as follows: It assumes that a person can maintain weight at a daily intake of the calories assumed to equal one pound of fat. If we think one pound equals 3,500 calories and in fact one pound equals 2,843 calories, over a year, 657 ‘extra’ calories a day, simply from the formula ‘being wrong’, would add up to 239,805 extra calories and this, divided by 2,843 gives 84 pounds.

Ref 1:

Ref 2: Dr. Geoffrey Livesey, “The Calorie Delusion: Why food labels are wrong”, New Scientist, (15 July 2009). FAO Food & Nutrition paper 77: “Food energy - methods of analysis and conversion factors”, Report of a Technical Workshop, Rome, (December 2002).

Ref 3: Max Wishnofsky, "Caloric equivalents of gained or lost weight", The American Journal of Clinical Nutrition, (1958).

Ref 4: Bozenraad, Deutsche Archives Internal Medicine, (1911).

Where did this come from?

Lulu Hunt Peters (1918)

In a book called Diet and Health by Lulu Hunt Peters (1918),[i] Hunt Peters states “Five hundred Calories equal approximately 2 ounces of fat. Two ounces per day would be about 4 pounds per month, or 48 pounds per year. Cutting out 1000 Calories per day would equal a reduction of approximately 8 pounds per month, or 96 pounds per year.” An article from the Chicago Daily Tribune (Sept 15, 1959) asserts “a pound of fat is lost whenever the body burns up 3,500 calories by diet or exercise”.[ii] The way that this is asserted, suggests that it is already a well known ‘fact’ by this date, but did Hunt Peters start it or perpetuate it? A couple of extracts in Diet and Health make me think that it is plausible that Hunt Peters did effectively originate “The Calorie Formula”

Adapted from: Harcombe, Z. (n.d.). Where does the 3500 calorie theory come from? Retrieved March 03, 2017, from

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