Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule

Abstract

Despite theoretical evidence that the model commonly referred to as the 3500-kcal rule grossly overestimates actual weight loss, widespread application of the 3500-kcal formula continues to appear in textbooks, on respected government- and health-related websites, and scientific research publications. Here we demonstrate the risk of applying the 3500-kcal rule even as a convenient estimate by comparing predicted against actual weight loss in seven weight loss experiments conducted in confinement under total supervision or objectively measured energy intake. We offer three newly developed, downloadable applications housed in Microsoft Excel and Java, which simulates a rigorously validated, dynamic model of weight change. The first two tools available at http://www.pbrc.edu/sswcp, provide a convenient alternative method for providing patients with projected weight loss/gain estimates in response to changes in dietary intake. The second tool, which can be downloaded from the URL http://www.pbrc.edu/mswcp, projects estimated weight loss simultaneously for multiple subjects. This tool was developed to inform weight change experimental design and analysis. While complex dynamic models may not be directly tractable, the newly developed tools offer the opportunity to deliver dynamic model predictions as a convenient and significantly more accurate alternative to the 3500-kcal rule.

Figure 1

Panel A Actual change in weight versus 3500 kcal rule predicted change in weight (kg) with the 3500 kcal rule using raw data from (–18). Panel B Actual change in weight versus the dynamic model predicted change in weight (kg)^†. The 3500 kcal rule overestimates weight loss in most cases. ^†The dynamic model was simulated solely for caloric restriction studies which published necessary individual subject inputs such as age, height, gender, and baseline weight (, –17).

Figure 1

Panel A Actual change in weight versus 3500 kcal rule predicted change in weight (kg) with the 3500 kcal rule using raw data from (–18). Panel B Actual change in weight versus the dynamic model predicted change in weight (kg)^†. The 3500 kcal rule overestimates weight loss in most cases. ^†The dynamic model was simulated solely for caloric restriction studies which published necessary individual subject inputs such as age, height, gender, and baseline weight (, –17).

Figure 2

Figure 2 A Simulation of weight loss calculated with the 3500 kcal rule (red line) and a dynamic weight loss model (2) (blue line) for a 103 kg (227 lb) male with a caloric deficit of 867 kcal/d in the CALERIE trial(17). Based on repeated measures of body composition and energy expenditures, this subject was considered compliant because actual and prescribed energy intakes were within ±1%. Figure 2 B Long-term predictions of weight loss for the same subject (17) undergoing 25% caloric restriction demonstrate the discrepancy between weight loss predicted with the 3500 kcal rule and the dynamic model (2), the latter of which predicts a weight plateau after 1.4 years.

Figure 2

Figure 2 A Simulation of weight loss calculated with the 3500 kcal rule (red line) and a dynamic weight loss model (2) (blue line) for a 103 kg (227 lb) male with a caloric deficit of 867 kcal/d in the CALERIE trial(17). Based on repeated measures of body composition and energy expenditures, this subject was considered compliant because actual and prescribed energy intakes were within ±1%. Figure 2 B Long-term predictions of weight loss for the same subject (17) undergoing 25% caloric restriction demonstrate the discrepancy between weight loss predicted with the 3500 kcal rule and the dynamic model (2), the latter of which predicts a weight plateau after 1.4 years.