Role of Set.point
Theory
in Regulation
of Body Weight
weight is stable over long periods of time is untenable. It may be fundamental to set-point theory but it is surely erroneous.
Dear Dr. Whelan: We are surprised that no FASEBJ reader has so far challenged the assertion that adult human body weight “is maintained at a relatively stable level for long periods of time” given as a fundamental to set-point theory (1). On the average, adult body weight gains close to 0.4 kg/year in American women during the 3rd, 4th, and 5th decades (a little less in men). However women of low socioeconomic status (SES) gain far more and high SES women add less (2). Over a 3-year period (and in a defined demographic population) adults change weight in both directions, and individual excursions in excess ± 5 kg are not uncommon in both sexes. Obese individuals, of course, are notably weight labile and some gain or lose far more than 10 kg in as few as 3 years (3). Over an 8.3-year period and in the same demographic population, we now find that the root mean square (RMS) weight fluctuation is of the order of ±6.5 kg in both sexes or ±8.8% in men and ± 10% in women. Because most of the weight fluctuation is due to changes in the weight of fat (FW), it is not surprising that RMS changes in fat weight prove to be on the order of ± 50%. Some men and women gain or lose as much as 25 kg over 8.3 years, and only a tiny minority are stable within the limits set by minor fluctuations in hydration, fecal mass, readout accuracy, etc. Increasingly, the nutritional and epidemiological literature has come to emphasize weight variability and its possible implications to long-term morbidity and mortality (4, 5). Under these circumstances, and with such evidence, the assertion that the adult body
Author’s
Reply:
Dear Dr. Whelan, I would like to comment on Dr. Garn’s letter. In the abstract of my review article (1), the statement “In adult individuals body weight is maintained at a relatively stable level” should, in retrospect, have been written as ‘In a majority of adult individuals . . . ‘ The qualificalion of “relative” was included to account for established evidence that fluctuations in body weight occur over time. It was not intended to imply that the only changes in the body weight of an individual are those associated with hydration, gut fill, etc. As Dr. Garn has noted, the weight of individuals may vary by ± 5 kg around a mean over a period of 3 years. Making the conservative assumptions that 74% of weight change is fat and the remainder is lean body mass, of which only 20% is protein (2), that the energy cost of depositing 1 g of fat is 50.2 kJ, the cost of depositing 1 g of protein is 36.2 kJ (2, 3), and that daily energy intake is approximately 8360 kJ/day (2000 kcal/day), it is possible to calculate the energy associated with a gain or less of 5 kg body weight. In the situation of weight loss, energy lost as fat would be 139.2 megajoule (MJ) and that lost as protein would be 4.3 MJ, making a total of 144 MJ. During the same 3-year period energy intake would be approximately 9154 MJ so that a 5 kg weight loss would represent a 1.6% error in energy balance. In a situation of weight gain, the error in balance would be largely due to the energy cost associated with gaining body mass. Using the figures described above, the total excess energy intake required to account for a 5 kg weight gain would be 195 MJ (185.7 MJ for fat and 9.4 MJ for protein), representing an error of 2.1%. As these changes in body weight occur in both directions, representing an oscillation around a mean weight (with 5 kg being the maximum amplitude of the deviation), it appears that even 2% errors in energy balance are corrected over time. Obese individuals, representing 12% of the U.S. population (4), experience larger and faster weight changes, and a weight gain of 10 kg in 3 years would represent an error in energy balance of 4.0-4.5%, assuming an energy intake of 8360 kJ/day. The article recently published by Lissner et al. (5) used data from the Framingham study to demonstrate that individuals who ex-
Stanley M. Garn, Ph.D. Center for Human Growth and Development University of Michigan 300 N. Ingalls Ann Arbor, MI 48109-0406, USA
REFERENCES 1. Harris, R. B. S. (1990) Role of set-point theory in regulation of body weight. FASEBJ 4, 3310-3318 2. Garn, S. M., Bailey, S. M., and Higgins, I. T. T. (1980) Effects of socioeconomic status, family line, and living together on fatness and obesity. In Childhood Prevention of Atherosclerosis and Hypertension (Lauer, R. M., and Shekelle, R. B., eds) pp. 187-204, New York 3. Garn, S. M., and Pilkington, J. J. (1984) Comparison of threeyear weight and fat change distributions of lean and obese individuals. Ecol. Food Nutr. 15, 7-12 4. Lissner, L., et al. (1991) Variability of body weight and health outcomes in the Framingham population. N Engl. j Med. 324, 1839-1844 5. Hubert, H. B., Eaker, E. D., Garrison, R. J., and Castelli, R. P. (1987) Life-style correlates of risk factor change in young adults: an eight-year study of coronary heart disease risk factors in the Framingham offspring. Am. j Epidemiol. 125, 812-831
perienced frequent or large fluctuations in body weight were at higher risk for mortality than those who did not undergo such changes. It is not possible to determine from this paper either the frequency or the magnitude of weight change associated with increased risk, as analysis was based on a comparison between the upper and lower third of individual variations in body mass index (weight/height2). However, the authors raise an interesting question: As obese people are already at risk for disease, if weight cycling results in equal risk, then should they be counseled to lose weight? The obvious answer is to provide a means of successful and permanent weight loss, which probably cannot be achieved until we have a better understanding of the physiological and psychological mechanisms that allow many other individuals to maintain a healthy body weight. Ruth B. S. Harris, Ph.D. Nutrition Department
Kraft General Foods Glenview, IL 60025, USA REFERENCES 1. Harris, R. B. 5. (1990) Role of set-point theory in regulation of body weight. FASEBJ. 4, 3310-3318 2. Forbes, G. B., Brown, M. R., Welle, S. L., and Lipinski, B. A. (1986) Deliberate overfeeding in women and men: energy cost and composition of the weight gain. Br. j Nutr. 56, 1-9 3. Spady, D. W., Payne, P. R., Picou, D., and Waterlow,J. C. (1976) Energy balance during recovery from malnutrition. Am. j Clin. Nutr. 29, 1073-1088 4. Lissner, L., Odel, P. M., D’Agostino, R. B., Stokes, J., Kreger, B. E., Belanger, A. J., and Brownell, K. D. (1991) Variability of body weight and health outcomes in the Framingham population. N Engl. j Med. 324, 1839-1844 5. Committee on Diet and Health, Food and Nutrition Board, Commission on Life Sciences, National Research Council. (1989) Extent and distribution of chronic disease: an overview. In Diet and Health. Implications for Reducing Chronic Disease Risk, pp. 115, National Academy Press, Washington, D.C.
LETTERS TO THE EDITOR 794 Vol. 6 January 1992 www.fasebj.org by Univ of So Dakota Lommen Hlth Sci Library (192.236.36.29) on August 17, 2018. The FASEB Journal Vol. ${article.issue.getVolume()}, No. ${article.issue.getIssueNumb
Theory
in Regulation
of Body Weight
weight is stable over long periods of time is untenable. It may be fundamental to set-point theory but it is surely erroneous.
Dear Dr. Whelan: We are surprised that no FASEBJ reader has so far challenged the assertion that adult human body weight “is maintained at a relatively stable level for long periods of time” given as a fundamental to set-point theory (1). On the average, adult body weight gains close to 0.4 kg/year in American women during the 3rd, 4th, and 5th decades (a little less in men). However women of low socioeconomic status (SES) gain far more and high SES women add less (2). Over a 3-year period (and in a defined demographic population) adults change weight in both directions, and individual excursions in excess ± 5 kg are not uncommon in both sexes. Obese individuals, of course, are notably weight labile and some gain or lose far more than 10 kg in as few as 3 years (3). Over an 8.3-year period and in the same demographic population, we now find that the root mean square (RMS) weight fluctuation is of the order of ±6.5 kg in both sexes or ±8.8% in men and ± 10% in women. Because most of the weight fluctuation is due to changes in the weight of fat (FW), it is not surprising that RMS changes in fat weight prove to be on the order of ± 50%. Some men and women gain or lose as much as 25 kg over 8.3 years, and only a tiny minority are stable within the limits set by minor fluctuations in hydration, fecal mass, readout accuracy, etc. Increasingly, the nutritional and epidemiological literature has come to emphasize weight variability and its possible implications to long-term morbidity and mortality (4, 5). Under these circumstances, and with such evidence, the assertion that the adult body
Author’s
Reply:
Dear Dr. Whelan, I would like to comment on Dr. Garn’s letter. In the abstract of my review article (1), the statement “In adult individuals body weight is maintained at a relatively stable level” should, in retrospect, have been written as ‘In a majority of adult individuals . . . ‘ The qualificalion of “relative” was included to account for established evidence that fluctuations in body weight occur over time. It was not intended to imply that the only changes in the body weight of an individual are those associated with hydration, gut fill, etc. As Dr. Garn has noted, the weight of individuals may vary by ± 5 kg around a mean over a period of 3 years. Making the conservative assumptions that 74% of weight change is fat and the remainder is lean body mass, of which only 20% is protein (2), that the energy cost of depositing 1 g of fat is 50.2 kJ, the cost of depositing 1 g of protein is 36.2 kJ (2, 3), and that daily energy intake is approximately 8360 kJ/day (2000 kcal/day), it is possible to calculate the energy associated with a gain or less of 5 kg body weight. In the situation of weight loss, energy lost as fat would be 139.2 megajoule (MJ) and that lost as protein would be 4.3 MJ, making a total of 144 MJ. During the same 3-year period energy intake would be approximately 9154 MJ so that a 5 kg weight loss would represent a 1.6% error in energy balance. In a situation of weight gain, the error in balance would be largely due to the energy cost associated with gaining body mass. Using the figures described above, the total excess energy intake required to account for a 5 kg weight gain would be 195 MJ (185.7 MJ for fat and 9.4 MJ for protein), representing an error of 2.1%. As these changes in body weight occur in both directions, representing an oscillation around a mean weight (with 5 kg being the maximum amplitude of the deviation), it appears that even 2% errors in energy balance are corrected over time. Obese individuals, representing 12% of the U.S. population (4), experience larger and faster weight changes, and a weight gain of 10 kg in 3 years would represent an error in energy balance of 4.0-4.5%, assuming an energy intake of 8360 kJ/day. The article recently published by Lissner et al. (5) used data from the Framingham study to demonstrate that individuals who ex-
Stanley M. Garn, Ph.D. Center for Human Growth and Development University of Michigan 300 N. Ingalls Ann Arbor, MI 48109-0406, USA
REFERENCES 1. Harris, R. B. S. (1990) Role of set-point theory in regulation of body weight. FASEBJ 4, 3310-3318 2. Garn, S. M., Bailey, S. M., and Higgins, I. T. T. (1980) Effects of socioeconomic status, family line, and living together on fatness and obesity. In Childhood Prevention of Atherosclerosis and Hypertension (Lauer, R. M., and Shekelle, R. B., eds) pp. 187-204, New York 3. Garn, S. M., and Pilkington, J. J. (1984) Comparison of threeyear weight and fat change distributions of lean and obese individuals. Ecol. Food Nutr. 15, 7-12 4. Lissner, L., et al. (1991) Variability of body weight and health outcomes in the Framingham population. N Engl. j Med. 324, 1839-1844 5. Hubert, H. B., Eaker, E. D., Garrison, R. J., and Castelli, R. P. (1987) Life-style correlates of risk factor change in young adults: an eight-year study of coronary heart disease risk factors in the Framingham offspring. Am. j Epidemiol. 125, 812-831
perienced frequent or large fluctuations in body weight were at higher risk for mortality than those who did not undergo such changes. It is not possible to determine from this paper either the frequency or the magnitude of weight change associated with increased risk, as analysis was based on a comparison between the upper and lower third of individual variations in body mass index (weight/height2). However, the authors raise an interesting question: As obese people are already at risk for disease, if weight cycling results in equal risk, then should they be counseled to lose weight? The obvious answer is to provide a means of successful and permanent weight loss, which probably cannot be achieved until we have a better understanding of the physiological and psychological mechanisms that allow many other individuals to maintain a healthy body weight. Ruth B. S. Harris, Ph.D. Nutrition Department
Kraft General Foods Glenview, IL 60025, USA REFERENCES 1. Harris, R. B. 5. (1990) Role of set-point theory in regulation of body weight. FASEBJ. 4, 3310-3318 2. Forbes, G. B., Brown, M. R., Welle, S. L., and Lipinski, B. A. (1986) Deliberate overfeeding in women and men: energy cost and composition of the weight gain. Br. j Nutr. 56, 1-9 3. Spady, D. W., Payne, P. R., Picou, D., and Waterlow,J. C. (1976) Energy balance during recovery from malnutrition. Am. j Clin. Nutr. 29, 1073-1088 4. Lissner, L., Odel, P. M., D’Agostino, R. B., Stokes, J., Kreger, B. E., Belanger, A. J., and Brownell, K. D. (1991) Variability of body weight and health outcomes in the Framingham population. N Engl. j Med. 324, 1839-1844 5. Committee on Diet and Health, Food and Nutrition Board, Commission on Life Sciences, National Research Council. (1989) Extent and distribution of chronic disease: an overview. In Diet and Health. Implications for Reducing Chronic Disease Risk, pp. 115, National Academy Press, Washington, D.C.
LETTERS TO THE EDITOR 794 Vol. 6 January 1992 www.fasebj.org by Univ of So Dakota Lommen Hlth Sci Library (192.236.36.29) on August 17, 2018. The FASEB Journal Vol. ${article.issue.getVolume()}, No. ${article.issue.getIssueNumb
