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Nyenwe et al. (1) address an interesting and important topic of the effects or associations of parental diabetes with offspring outcomes. However, the paper contains an important error that renders one of their conclusions markedly incorrect.
Specifically, having estimated a difference in energy expenditure among offspring of parents with diabetes (which the authors refer to as ‘parental diabetes’) versus offspring of parents without diabetes, the authors project that persons with parental diabetes will, as a result of this difference, steadily gain substantial weight indefinitely. They state:
“According to the data published by Wishnofsky (2), one pound has a caloric value of 3500 kcal or (1 kg=7700 kcal). We derived the estimated weight gain in kg by dividing the projected energy accrual by 7700. When normalized REE is used for this estimation, subjects with parental diabetes had a daily energy surplus of 125 kcal which would translate to ~6 kg weight gain per year.”
This type of estimation is commonly referred to as the 3500 kcal rule or 3500 kcal per pound rule.
This reasoning and calculation is erroneous because it fails to account for the dynamic changes of energy expenditure that occur with weight gain and loss. Wishnofsky himself noted the complexity of estimating energetic equivalents of gaining or losing body weight, specifically addressing the importance of time, nitrogen balance, tissue type, and water loss, among other factors, on...
This reasoning and calculation is erroneous because it fails to account for the dynamic changes of energy expenditure that occur with weight gain and loss. Wishnofsky himself noted the complexity of estimating energetic equivalents of gaining or losing body weight, specifically addressing the importance of time, nitrogen balance, tissue type, and water loss, among other factors, on estimating the energetic equivalent of one pound of body weight (2, 3). He did not imply that 3500 kcal should be used as the equivalent of one pound of weight in all cases and extrapolated indefinitely.
Over very short periods of time, such a linear projection might be a reasonable rough approximation, but over periods of months or years, the 3500 kcal rule can lead to order-of-magnitude overestimates of weight changes in response to energy intake or expenditure variations (4). This has been noted repeatedly in the literature (5-8), including prominent journals such as New England Journal of Medicine (9), The Journal of the American Medical Association (10, 11), and The Lancet (12). This error has resulted in at least one paper being retracted (13).
Validated mathematical models have been developed to account for the dynamic changes in energy expenditure that occur with weight gain and loss (12). Using such a model, we calculated that the observed 125 kcal/d difference in energy expenditure would produce a total weight change of ~6.5 kg, with ~3.9 kg gained in the first year and 95% of the total gained in 3 years. These model calculations incorporated the baseline demographics and anthropometrics reported by Nyenwe et al. and assumed that the subjects had a constant energy intake and a physical activity level of 1.7. Even the simple 10 kcal/d per pound rule of thumb (or equivalently 100 kJ/d per kg) derived from a more detailed mathematical model (12) predicts a total weight change of ~6 kg, with half of the gain occurring in the first year and 95% of the total gain in 3 years. These estimates stand in marked contrast to the predicted ~6 kg of weight gain every year stated by Nyenwe et al.
We encourage the authors to revise their conclusion regarding projected weight effects of the estimated differences in energy expenditure.
1. Nyenwe EA, Ogwo CC, Owei I, et al. Parental history of type 2 diabetes is associated with lower resting energy expenditure in normoglycemic subjects. BMJ Open Diabetes Research & Care 2018;6(1) doi: https://www.doi.org/10.1136/bmjdrc-2018-000511
2. Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr 1958;6(5):542-6. https://doi.org/10.1093/ajcn/6.5.542
3. Wishnofsky M. Caloric equivalents of gained or lost weight. JAMA 1960;173(1):85. doi: https://www.doi.org/10.1001/jama.1960.03020190087024
4. Brown AW, Hall KD, Thomas D, et al. Order of Magnitude Misestimation of Weight Effects of Children's Meal Policy Proposals. Childhood Obesity 2014;10(6):542-5. doi: https://www.doi.org/10.1089/chi.2014.0081
5. Hall KD, Chow CC. Why is the 3500 kcal per pound weight loss rule wrong? International Journal of Obesity 2013;37(12):10.1038/ijo.2013.112. doi: https://www.doi.org/10.1038/ijo.2013.112
6. Thomas DM, Martin CK, Lettieri S, et al. Response to 'why is the 3500 kcal per pound weight loss rule wrong?'. Int J Obes 2013;37(12):1614-5. doi: https://www.doi.org/10.1038/ijo.2013.113
7. Thomas DM, Martin CK, Lettieri S, et al. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule. Int J Obes 2013;37(12):1611-3. doi: https://www.doi.org/10.1038/ijo.2013.51
8. Bohan Brown MM, Brown AW, Allison DB. Linear extrapolation results in erroneous overestimation of plausible stressor-related yearly weight changes. Biological Psychiatry 2014 doi: https://www.doi.org/10.1016/j.biopsych.2014.10.028
9. Casazza K, Fontaine KR, Astrup A, et al. Myths, presumptions, and facts about obesity. N Engl J Med 2013;368(5):446-54. doi: https://www.doi.org/10.1056/NEJMsa1208051
10. Hall KD, Schoeller DA, Brown AW. Reducing calories to lose weight. JAMA 2018;319(22):2336-37. doi: https://www.doi.org/10.1001/jama.2018.4257
11. Allison DB, Thomas DM, Heymsfield SB. Energy intake and weight loss. JAMA 2014;312(24):2687-88. doi: https://www.doi.org/10.1001/jama.2014.15513
12. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378(9793):826-37. doi: https://www.doi.org/10.1016/S0140-6736(11)60812-X
13. Retraction of “Modeling Potential Effects of Reduced Calories in Kids' Meals with Toy Giveaways”. Childhood Obesity 2014;10(6):546-46. doi: https://www.doi.org/10.1089/chi.2014.1062