Reply to SB Roberts et al

Department of Psychiatry, School of Medicine, University of Pennsylvania, 3600 Market Street, Philadelphia, PA 19104-2648, E-mail: stunkard{at}mail.med.upenn.edu
Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104
Department of Pediatrics, University of Pennsylvania, Philadelphia, PA 19104
Department of Nutritional Sciences, University of Wisconsin, Madison, WI 53706

We appreciate the opportunity to respond to the letter of Roberts et al. Their substantive criticism of our paper (1) is that we "did not study infants becoming overweight." In fact, we did and we will review these findings. We studied 78 infants at high or low risk of obesity on the basis of maternal obesity or leanness. In this sample, energy intake at 3 mo of age contributed significantly to body weight and weight-for-length at 1 y of age and maternal obesity and energy expenditure did not. In fact, total energy expenditure at 3 mo (n = 42) was positively correlated with weight (r = 0.67) and with weight-for-length (r = 0.57) at 1 y of age. Similar findings were also reported by Davies et al (2) and Wells et al (3).

In their study of 18 subjects, Roberts et al (4) reported that low total energy expenditure at 3 mo predicted excess weight gain in 6 subjects of obese mothers. Because this finding differed from our results, as reported in our paper, we matched 6 of our subjects at 1 y of age with the 6 overweight subjects studied by Roberts et al by body mass index (18.8; in kg/m²). As in our sample as a whole, neither total nor sleeping energy expenditure at 3 mo made any significant contribution to the body weights of these matched subjects at 1 y of age. A review of studies of the relation between the weights of parents and of those of their offspring in the first 2 y of life revealed that only 2 found such a relation whereas 6 did not (5).

The letter by Roberts et al states that we implied that our results refuted the findings of 3 other studies (6–8) regarding the effect of energy expenditure on subsequent body weight. We did not suggest that we had refuted these findings. The other studies dealt with older children and we specifically noted that "because our results are limited to the first year of life, effects of the risk factors that we examined may differ at later ages."

We recognize the pioneering contributions of Roberts and her colleagues to the development of studies of high-risk obesity. The power of this method is becoming increasingly apparent. As our cohort of children enter their sixth year, we expect to make further contributions to our understanding of the growth and development of persons at high risk of obesity. The findings of our current report, however, deal only with the period from 3 to 12 mo.

REFERENCES

1. Stunkard AJ, Berkowitz RI, Stallings VA, Schoeller DA. Energy intake, not energy output, is a determinant of body size in infants. Am J Clin Nutr 1999;69:524–30.
2. Davies P, Day J, Lucas A. Energy expenditure in early infancy and later body fatness. Int J Obes 1991;15:727–31.
3. Wells JCK, Stanley M, Laidlaw AS, Day JME, Davies PSW. The relationship between components of infant energy expenditure and childhood body fatness. Int J Obes Relat Metab Disord 1996;20:848–53.
4. Roberts SB, Savage J, Coward WA, Chew B, Lucas A. Energy expenditure and intake in infants born to lean and overweight mothers. N Engl J Med 1988;318:461–6.
5. Stunkard AJ, Berkowitz RI, Stallings VA, Cater JR. Weights of parents and infants: is there a relationship? Int J Obes Relat Metab Disord 1999;23:159–62.
6. Griffiths M, Payne PR, Stunkard AJ, Rivers JPW, Cox M. Metabolic rate and physical development in children at risk of obesity. Lancet 1990;336:76–8.
7. Griffiths M, Payne PR. Energy expenditure in small children of obese and nonobese parents. Nature 1976;260:698–700.
8. Delany JP, Harsha DW, Bray GA. Reduced energy expenditure predicts increase in body fat in boys. Am J Clin Nutr 1997;66:205 (abstr).