Is this long known formula true? I've seen people lose as much as 1lb a day on 400 cals a day diets on things such as the potato diet, or just low calorie like that in general, for as long as 3 weeks, which definitely can't be all water weight. Maybe not healthy, but that totally detests that "proven" equation. Has anyone lost weight in a certain amount of time that also goes against this "proven" formula? Please share!
asked byAmber_7 (748)
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on December 16, 2012
at 10:57 AM
Question: I've seen people lose as much as 1lb a day on 400 cals a day diets...
When you see somebody lose a pound a day, a lot of it is temporary water loss. It's unlikely that anyone can continue to lose weight that fast over the long run. The fastest prolonged weight loss that has been recorded in any scientific paper that I've seen was about three-quarters of a pound per day.(1) The person in that study was an extremely large man (he weighed 456 pounds at the beginning of the study) with high metabolic requirements who ate nothing at all.
Question: Losing 1lb Equals Burning 3500 cals? ... Is this long known formula true?
It's a misunderstanding based on the fact that if a surgeon removes a piece of fat tissue from your body, that tissue will contain about 3500 kcal per pound. But when you lose weight naturally, by eating less, it's not the same thing as surgery. When you lose weight naturally, you don't lose pure blobs of fat tissue. The stuff cut out by the surgeon is called adipose tissue, but the stuff you lose naturally is sometimes called "obesity tissue." They are not the same thing, and they don't have the same caloric values.
Various researchers have published caloric values of obesity tissue between 2600 kcal/kg (1180 kcal/lb) and 10000 kcal/kg (4545 kcal/lb).(4)
The misunderstanding apparently originated in a radio show interview with Dr. George Cahill in the 1960s or 70s. Dr. Cahill should be of interest to paleo dieters because he's the most important scientist in the history of ketosis research. One of his students, Dr. Oliver Owen (who is also an important scientist in ketosis research) describes what happened in a book:
Dr. Oliver Owen wrote:
When I was studying starving obese volunteers and training under the direction of Dr. George F. Cahill, Jr. at Harvard, the questions arose regarding the caloric value of adipose (fat) tissue. We made arrangements with Dr. Francis Moore, Professor and Chair, Surgery, at the Peter Bent Brigham to provide us with small fragments of abdominal fat tissue obtained at the time of abdominal operations. This was approved, and we analyzed the adipose tissue for caloric content. Dr. Cahill particpated in a live radio talk show in Boston. He said the caloric value of adipose tissue was about 3500 Kcal/pound (7700 Kcal/kg). This value spread across the nation faster than any of our carefully defined scientific facts did. It was not, however, an accurate caloric value for a pound (or kg) of gained or lost body weight.
Changes in total body fat mass are accompanied by changes in total body lean mass. Thus, changes in gains or losses of obesity tissue are different from isolated adipose tissue. During weight gain, more lean body mass (muscle, blood, extracellular fluid, connective tissue and skin) is needed to support and maintain the accumulated adipose tissue. Obesity tissue is about 14 percent fluid, 62 percent fat (triglycerides) and 24 percent active protoplasmic tissue. This latter mass is mostly water: 80 percent water which contains primarily proteins suspended in a salt solution. Thus, the energy equivalent of obesity tissue is not equal to that of fat under the skin. Instead, obesity tissue is only about 2600 Kcal/pound (5720 Kcal/kg).(2)
Other researchers have come up with drastically different caloric values for obesity tissue. Here's a quote from a paper by Passmore et al. (1958):
Caloric value of obesity tissue. The variations in water loss alter this value greatly. The overall figure of 7000-8000 Cal./kg of obesity tissue, which was found for all the patients, masks the weekly changes. During the 1st week, when water losses were high, the values were less than 5000 Cal./kg. In subsequent weeks, they were much greater and, when water was being retained, over 10,000 Cal./kg. Keys & Bro??ek (1953) calculated the change in body composition in a group of mental patients, whose metabolism appeared to be normal during a period of overfeeding. They calculated that the mean calorie value of the obesity tissue gained was 6700 Cal./kg. Subsequently, in a study of young men on a restricted ration, Bro??ek, Grande, Taylor, Anderson, Buskirk & Keys (1957) reported values for the tissue lost varying between 2600 and 8700 Cal./kg.(3)
Note that Passmore et al. found that the average caloric value of obesity tissue is close to 3500 kcal per pound. However they found a large variance.
The concept of "obesity tissue" was introduced by Ancel Keys and Josef Bro??ek in a 1953 paper that has been cited 805 times, according to Google Scholar.(4)
Stewart WK, Fleming LW. Features of a successful therapeutic fast of 382 days' duration. Postgrad Med J. 1973 Mar;49(569):203-9. http://pmid.us/4803438
Owen, Oliver E. Searching for Medical Truths. Infinity Publishing: 2006. Page 250.
Passmore R, et al. The chemical composition of the tissue lost by obese patients on a reducing regimen. Br J Nutr. 1958;12(1):113-22. PMID: 13523109.
Keys A, Bro??ek J. Body fat in adult man. Physiol Rev. 1953 Jul;33(3):245-325. PMID: 1308829