Is the dieting rule – 3,500 calories per pound weight loss – correct?
By Monica Mollica via BrinkZone.com
A pervasive dieting mantra is that a cumulative reduction of caloric intake of 3,500 will result in a weight loss of 1 pound. This dieting rule popularly states “because 3,500 calories equals about 1 pound (0.45 kilogram) of fat, if you cut 500 calories from your diet each day, or burn 500 calories extra per day from exercising (or a combination thereof) you’d lose about 1 pound a week (500 calories x 7 days = 3,500 calories) and 52 pounds in a year.
This simple weight loss rule continues to be cited on weight loss websites as well as authoritative nutrition textbooks [1, 2], scientific articles [3-6], and expert guidelines.[7] It is even common among health care professionals to believe in the 3,500 calorie rule [8], and the Patient Page on “Healthy weight loss” at The Journal of the American Medical Association website states in the first sentence on “What you need to know about weight loss” that… “A total of 3,500 calories equals 1 pound of body weight. This means if you decrease (or increase) your intake by 500 calories daily, you will lose (or gain) 1 pound per week (500 calories per day × 7 days = 3,500 calories).” [9]
However, is this really true? Most people who have ever been on a diet are probably skeptical. And rightly so. In this article I will highlight what’s wrong with the 3,500 calorie rule and present a more accurate calculator that you can use to more precisely predict how much weight loss you can except in real life from a given daily calorie reduction.
What’s wrong with the “3,500 calorie per pound weight loss” rule?
The 3,500 calorie rule is based on a calculation – first published 1952 – that assumes exclusive loss of adipose tissue consisting of 87% fat.[10, 11]
However, in real life, during weight loss lean body mass is lost together with body fat [12-14] and the composition of weight loss (i.e. the relative proportion of lean and fat) is influenced by several factors, such as exercise [15-17], protein intake [15, 18-20], as well as testosterone [21-23] and thyroid hormone status.[24, 25] And making it even more inaccurate, the original “3,500 calorie per pound weight loss” rule is popularly misrepresented by replacing “weight” with “fat” loss.[26]
The main scientific criticism of 3,500 calorie rule is that in real life, there is self-limiting nature of weight loss imposed by a constant caloric deficit. As you lose weight, your body will progressively burn less calories as your weight drops (more on that below), so that over time – even if you adhere to your caloric restriction – the imposed calorie deficit will have a smaller impact and your rate of weight loss will therefore slow down (unless you restrict your calories more or exercise more).[14, 27-33] To clarify, if you lower intake by 500 kcal on diet day one, this closely approximates an energy deficit of -500 kcal, but the magnitude of this deficit and associated weight loss will decrease markedly over time.
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