A Prospective Study of Breakfast Consumption and Weight Gain among U.S. Men

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1 Diet and Physical Activity A Prospective Study of Breakfast Consumption and Weight Gain among U.S. Men Amber A.W.A. van der Heijden,* Frank B. Hu,* Eric B. Rimm,* and Rob M. van Dam* Abstract VAN DER HEIJDEN, AMBER A.W.A., FRANK B. HU, ERIC B. RIMM, AND ROB M. VAN DAM. A prospective study of breakfast consumption and weight gain among U.S. men. Obesity. 2007;15: Objective: The aim was to investigate the association between breakfast consumption and long-term weight gain in an adult male population. Research Methods and Procedures: We evaluated prospective data on 20,064 U.S men, 46 to 81 years of age, who participated in the Health Professionals Follow-up Study. Data on body weight, dietary factors, and lifestyle variables were obtained by validated questionnaires. We examined weight gain during 10 years of follow-up. Results: Overall, 5857 men had a weight gain of 5 kg or greater during 10 years of follow-up. Breakfast consumption was inversely associated with the risk of 5-kg weight gain after adjustment for age [hazard ratio (HR) 0.77 (95% confidence interval [CI], 0.72 to 0.82)], and this association was independent of lifestyle and BMI at baseline [HR 0.87 (95% CI, 0.82 to 0.93)]. Fiber and nutrient intakes partially explained the association between breakfast consumption and weight gain. The inverse association between breakfast consumption and weight gain was more pronounced in men with a baseline BMI of 25 kg/m 2 or lower [multivariate HR 0.78 (95% CI, 0.70 to 0.87)] than in men who were overweight at baseline [HR 0.92 (95% CI, 0.85 to 1.00)]. Furthermore, we observed that an increasing number of eating occasions in addition to three standard meals was associated with a higher risk of 5-kg Received for review January 23, Accepted in final form February 26, The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Departments of *Nutrition and Epidemiology, Harvard School of Public Health, Boston, Massachusetts; Institute of Health Sciences, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, The Netherlands; and Channing Laboratory, Department of Medicine, Brigham and Women s Hospital and Harvard Medical School, Boston, Massachusetts. Address correspondence to Amber A.W.A. van der Heijden, EMGO Institute, VU University Medical Center, van der Boechorststraat 7, 1081BT Amsterdam, The Netherlands. a.vanderheijden@vumc.nl Copyright 2007 NAASO weight gain [HR 1.15 (95% CI, 1.06 to 1.25, for 2 vs. 0 additional eating occasions)]. Discussion: These findings suggest that the consumption of breakfast may modestly contribute to the prevention of weight gain as compared with skipping breakfast in middleaged and older men. Key words: weight gain, overweight, eating behaviors, longitudinal Introduction The prevalence of overweight and obesity has rapidly increased during recent decades and is associated with an increased burden of chronic diseases such as cardiovascular diseases and cancer (1). The prevalence of people not consuming breakfast every day has increased over the last decades, in children, adolescents (2), and adults (3). The consumption of breakfast has been postulated to be an important factor in preventing weight gain. Breakfast consumption could reduce total caloric intake during the day by consuming less food later in the day (4), possibly as a result of more stable blood glucose levels in breakfast consumers as compared with breakfast non-consumers (5). Additionally, a higher frequency of meal consumption could have favorable effects on metabolic responses (6). The type of foods consumed at breakfast might contribute to a lower BMI by improving overall dietary intake (7), particularly the amount of fiber (8,9). Several cross-sectional studies reported inverse associations between the consumption of breakfast and BMI (8,10 12). However, the possibility exists that the observed inverse cross-sectional association between the consumption of breakfast and BMI is caused by the skipping of breakfast in overweight subjects in an attempt to reduce total energy intake. Few prospective studies have been performed to examine the association between breakfast consumption and weight gain in children (13), adolescents (14,15), and adults (16,17). The aim of the present study is to investigate the association between breakfast consumption and weight gain in an adult male population over a 10-year period. OBESITY Vol. 15 No. 10 October

2 Research Methods and Procedures Study Participants The Health Professionals Follow-up Study is a prospective cohort study of 51,529 U.S. male health professionals who were 40 to 75 years of age at study initiation in Information on lifestyle factors and health status was obtained using biennially mailed questionnaires. Dietary data were assessed every 4 years, using semi-quantitative food frequency questionnaires. In 1992, specific questions were added on consumption of breakfast and other eating occasions. Therefore, we used 1992 as baseline for the present analysis; 36,759 participants were still alive in 1992 and completed the 1992 questionnaire. We excluded men with missing values for breakfast consumption or BMI in 1992, men with implausibly low ( 800 kcal/d) or high ( 4200 kcal/d) total energy intake and men who had 70 blank items on the food frequency questionnaire. After these exclusions, 29,489 men remained. We also excluded men with a history of diabetes (n 1361), cardiovascular disease (n 3986), or cancer (except non-melanoma skin cancer) (n 1997) at baseline because these conditions could lead to changes in lifestyle and dietary habits or reporting thereof. Of the remaining persons, 1120 died during followup, and an additional 3080 men had missing values for BMI in 2002 (the end of follow-up for this analysis). After these exclusions, 20,064 men remained for the current analyses. The study was approved by the Institutional Review Board of the Harvard School of Public Health, and all participants gave informed consent through return of mailed questionnaires. Assessment of Diet and Potential Confounders In 1992, the questionnaire included the item Please indicate the times of day that you usually eat. The participants could mark all of the predefined answer categories that applied (before breakfast, breakfast, between breakfast and lunch, lunch, between lunch and dinner, dinner, between dinner and bedtime, and after going to bed). Nutrient intake was assessed from the 1990 semi-quantitative foodfrequency questionnaire that inquired about the average use of 130 foods and beverages during the previous year. We used nutrient intake data from 1990 because the foodfrequency questionnaire was not administered in The food-frequency questionnaire was validated previously among a subset of the participants against two 1-week dietary records (18). On the 1992 questionnaire, information was also requested about physical activity, smoking status, marital status, work status, personal history of cardiovascular diseases, diabetes, and cancer. The validity and reproducibility of the physical activity questionnaire have been assessed and described previously (19). Assessment of Weight Change and Weight Gain Participants reported their weight on each biennial questionnaire. Weight change was defined as the difference between weight reported in 2002 and at baseline in Substantial weight gain was defined as weight gain of 5 kg or greater during the 10-year follow-up period. Previously, we evaluated the reproducibility and validity of the selfreported measures of weight by using a subset of the cohort on whom technician-assessed measurements were taken. Self-reported weight and the average of two technician measures of weight were highly correlated at 0.97 (20). Statistical Analysis Age-adjusted and multivariate linear regression analysis was used to examine the association between the consumption of breakfast and weight change during 10 years of follow-up. Results of this analysis are expressed as means standard error. For the analysis with incidence of 5-kg weight gain as the outcome, the number of person-years of follow-up was computed for each participant from the return of date of the 1992 questionnaire to the return date of the questionnaire for which the incidence of 5-kg weight gain occurred, death from any cause, or return of the 2002 questionnaire, whichever came first. We used Cox proportional hazards models stratified by 5-year age categories and 2-year time periods to calculate the hazard ratio (HR) 1 for incidence of 5-kg weight gain. Multivariate models were used to calculate HRs adjusted for age, baseline BMI (kg/ m 2 ), smoking status (never, former, current), marital status (yes/no), work status (full-time, part-time, retired/disabled), physical activity (quintiles of metabolic equivalents tasks), weight training (yes/no), and alcohol intake (0, 0.1 to 4.9, 5.0 to 14.9, 15.0 to 29.9, or 30.0 g/d). Because a possible association between the consumption of breakfast and weight gain could be partly mediated by a more prudent dietary intake and less eating occasions between meals, we also conducted analyses with additional adjustment for percentage of energy from protein, total fat and trans-fat, polyunsaturated fat-to-saturated fat ratio, fiber intake (all in quintiles), consumption of food between breakfast and lunch (yes/no), consumption of food between lunch and dinner (yes/no), and consumption of food after dinner (yes/ no). Similar analyses were performed to investigate the association between the frequency of eating occasions and the risk of 5-kg weight gain. The p values for trend were calculated modeling frequency of eating occasions as a continuous variable. p Values for interaction were calculated by comparing models with and without inclusion of cross-product terms for breakfast (yes/no) and BMI (kg/m 2 ) and for breakfast (yes/no) and age (years) using the loglikelihood test. Stratified analyses were conducted according to categories of age and BMI. Because smoking status or 1 Nonstandard abbreviations: HR, hazard ratio; CI, confidence interval OBESITY Vol. 15 No. 10 October 2007

3 Table 1. Age-adjusted baseline characteristics according to breakfast consumption Breakfast nonconsumers Breakfast consumers p No. of participants Age (yrs) BMI (kg/m 2 ) Physical activity (metabolic equivalent/wk) Any weight training (%) Current smoker (%) Married (%) Work status Full-time (%) Part-time (%) Retired/disabled (%) Dietary intake Meals (no./day) Before breakfast (%) Between breakfast and lunch (%) Lunch (%) Between lunch and dinner (%) Dinner (%) Between dinner and bedtime (%) After going to bed (%) Alcohol (grams/day) Carbohydrate (energy %) Protein (energy %) Total fat (energy %) Polyunsaturated fat (energy %) Monounsaturated fat (energy %) Saturated fat (energy %) Trans-fat (energy %) Polysaturated fat-to-saturated fat ratio Fiber (grams/day) Whole grain (grams/day) Values are means or percentages. changes in smoking status could have an impact on weight, we analyzed the association between breakfast consumption and weight gain, while excluding current cigarette smokers in 1992 and We also performed the analysis with exclusion of men who developed chronic diseases during follow-up because this could influence dietary habits and weight. Because our definition of substantial weight change was arbitrary, we performed a sensitivity analysis using 10-kg weight gain as the outcome measure. We calculated 95% confidence intervals (CIs) for all HRs. All p values are two-tailed. Statistical analyses were performed using SAS statistical software (version 9.1; SAS Institute, Inc., Cary, NC). Results Baseline characteristics according to consumption of breakfast are presented in Table 1. Of all men, 46 to 81 years old, 16.9% reported not usually consuming breakfast. Men who consumed breakfast at baseline had a lower BMI, were less likely to smoke, and were more physically active. OBESITY Vol. 15 No. 10 October

4 Table 2. HRs of 5-kg weight gain among men according to breakfast consumption Breakfast non-consumers Breakfast consumers All men No. of men with 5-kg weight gain Person-years 27, ,865 5-kg weight gain/1000 person-years Age-adjusted HR* 1 (Referent) 0.77 (0.72 to 0.82) Multivariate HR 1 (Referent) 0.87 (0.82 to 0.93) Baseline BMI 25 kg/m 2 Age-adjusted HR* 1 (Referent) 0.70 (0.63 to 0.78) Multivariate HR 1 (Referent) 0.78 (0.70 to 0.87) Baseline BMI 25 kg/m 2 Age-adjusted HR* 1 (Referent) 0.86 (0.80 to 0.93) Multivariate HR 1 (Referent) 0.92 (0.85 to 1.00) HR, hazard ratio. * Adjusted for age (in 5-year categories). Further adjusted for baseline BMI (continuous), smoking status (never, former, current), marital status (yes/no), work status (full-time, part-time, retired/disabled), physical activity (quintiles of metabolic equivalents task hours), weight lifting (yes/no), and alcohol intake (0, 0.1 to 5.0, 5.1 to 14.0, 15 to 29, or 30.0 g/d). Furthermore, breakfast consumers had lower intakes of alcohol and fat and higher intakes of fiber and whole grains. A slightly lower 10-year weight gain was observed among men who consumed breakfast compared with men who did not consume breakfast, after adjustment for age ( vs kg, p 0.07) and adjustment for potential confounders ( vs kg, p 0.35), although these differences were not statistically significant. During 10 years of follow-up, 5857 men had a weight gain of 5 kg or more. Compared with men who did not consume breakfast, men who did consume breakfast had a 23% lower risk of a 5-kg weight gain after adjustment for age [HR 0.77 (95% CI, 0.72 to 0.82)] (Table 2). Further adjustment for potential confounders weakened the association [HR 0.87 (95% CI, 0.82 to 0.93)], and dietary factors explained part of the remaining association [(HR 0.91 (95% CI, 0.85 to 0.97)]. When we examined interactions of breakfast consumption with BMI and age in relation to risk of weight gain, we found a significant interaction for BMI (p 0.002) but not for age (p 0.14). The multivariate HR of 5-kg weight gain for breakfast consumption was 0.88 (95% CI, 0.82 to 0.94) for men younger than 65 and 0.74 (95% CI, 0.58 to 0.95) for older men. The inverse association between breakfast consumption and the risk of 5-kg weight gain was stronger in men with a BMI lower than 25 kg/m 2 at baseline than in men who were overweight at baseline (Table 2). When we examined the association between breakfast consumption and the risk of developing overweight (BMI 25 kg/m 2 ) among men who were not overweight at baseline, breakfast consumers had a lower risk of developing overweight as compared with breakfast non-consumers [multivariate HR 0.81 (95% CI, 0.72 to 0.91)]. The inverse association between breakfast consumption and weight gain became stronger after exclusion of smokers [multivariate HR 0.83 (95% CI, 0.75 to 0.92)]. In contrast to these results, exclusion of men who developed chronic diseases during follow-up or using substantial weight gain of 10 kg instead of 5 kg as the outcome did not materially change the association between breakfast consumption and weight gain ( 10% change in regression coefficients). We also examined the association between meal frequency and risk of weight gain. An increasing number of eating occasions in addition to three standard meals (breakfast, lunch, and dinner) was associated with a higher risk of 5-kg weight gain (Table 3). Additional adjustment for dietary factors did not materially change this association [HR 1.17 (95% CI, 1.08 to 1.28, for 2 vs. 0 additional eating occasions)]. Discussion In this prospective cohort study of men, the consumption of breakfast was modestly associated with lower risk of 5-kg weight gain during 10-years of follow-up. This inverse association was more pronounced in men with a baseline 2466 OBESITY Vol. 15 No. 10 October 2007

5 Table 3. HRs of 5-kg weight gain by number of eating occasions added to the three regular meals per day Breakfast-lunch-dinner 1 eating occasion/day >2 eating occasions/day p for trend Age-adjusted HR* 1 (referent) 1.13 (1.07 to 1.20) 1.23 (1.13 to 1.34) Multivariate HR 1 (referent) 1.07 (1.02 to 1.14) 1.15 (1.06 to 1.25) HR, hazard ratio. * Adjusted for age (in 5-year categories). Further adjusted for baseline BMI (continuous), smoking status (never, former, current), marital status (yes/no), work status (full-time, part-time, retired/disabled), physical activity (quintiles of metabolic equivalents task hours), weight lifting (yes/no), and alcohol intake (0, 0.1 to 5.0, 5.1 to 14.0, 15 to 29, or 30.0 g/d). BMI of 25 kg/m 2 or lower. In contrast, a greater frequency of eating occasions was associated with an increased risk of weight gain. Previous prospective studies demonstrated an inverse association between breakfast consumption and weight gain in children and adolescents (13 15). One study observed an inverse association between consumption of breakfast cereal and weight in adults (16). In contrast, in Dutch men around the age of retirement, an increased frequency of breakfast consumption was associated with increases in waist circumference during the same period. A reverse effect, an effect of perceived weight change on breakfast consumption habits may have contributed to the observed association in that study (17). In several cross-sectional studies among children and adults, the consumption of breakfast was associated with a lower BMI (8,10 12), which is consistent with the findings in the current study. Due to the cross-sectional design of most previous studies, the direction of the effects that resulted in an inverse association between breakfast consumption and BMI remained unclear. Our prospective study suggests that breakfast consumption may contribute to reduced weight gain. Several mechanisms to explain this putative effect of breakfast consumption have been postulated. Breakfast consumption could contribute to a greater meal frequency per day (as we found; Table 1). More meals per day could lead to less efficient energy use by increasing dietary-induced thermogenesis, which could result in a lower BMI (6,8,21). To our knowledge, no previous studies have investigated the association between meal frequency and weight prospectively. Although a clinical trial demonstrated favorable effects of increased meal frequency on metabolic risk factors and energy expenditure (22), our results suggest that under free-living conditions, a high number of eating occasions (eating occasions in addition to breakfast, lunch, and dinner) can contribute to weight gain. It, therefore, seems unlikely that the inverse association between breakfast consumption and the risk of 5-kg weight gain is due to a greater meal frequency. Breakfast consumption may prevent overeating during the day. Lower energy intake during the day was reported in a clinical trial that compared the effects of eating breakfast and skipping breakfast (23). During prolonged fasting, ghrelin levels rise (24) and insulin levels decline (25), which may trigger hunger and stimulate eating (26 28). Additionally, prolonged fasting can result in increased postprandial glucose levels and a greater subsequent decline in glucose levels (29). Dynamic declines in blood glucose levels can induce meal initiation that may contribute to excess energy intake (5). However, it is unclear to what extent these effects of prolonged fasting for 72 hours apply to the duration of fasting as a result of skipping breakfast. Breakfast consumption can also contribute to a better overall dietary intake, particularly because breakfasts are often high in fiber (7 9). However, adjustment for fiber and nutrient intakes did not fully explain the association between breakfast consumption and weight in the current study. Consistent with this observation, consumption of both whole-grain and refined grain breakfast cereals was associated with reduced weight gain in a previous study in U.S. men (16). Clearly, breakfasts can differ greatly in nutrient composition, fiber content, and energy density (30,31), and one would expect a stronger beneficial effect on weight control for consuming a breakfast of optimal composition than for consuming any breakfast. The inverse association between the consumption of breakfast and risk of weight gain was stronger in men with a BMI lower than 25 kg/m 2 as compared with men who were overweight. This tendency was also observed in longitudinal research in children and adolescents (15) but needs to be confirmed in further research. Several limitations of our study must be considered while interpreting the present results. First, a substantial part of the cohort was excluded for the current analysis. However, in a sensitivity analysis without exclusion of men with a history of diabetes, cardiovascular disease, or cancer at baseline, the results did not materially change (data not shown). Moreover, loss to follow-up rather than baseline OBESITY Vol. 15 No. 10 October

6 exclusions can lead to selection bias in prospective studies. The rate of follow-up was high in our study, and usual breakfast consumption was similar for those who were lost to follow-up and our analytical study population (15.6% and 16.9% respectively). Second, breakfast consumption has been associated with higher age, income, and education level (3) and with health-conscious behaviors (8,10,32). Because of the observational design of this study, residual confounding by a healthy eating pattern and lifestyle associated with eating breakfast cannot be completely ruled out. However, we were able to adjust extensively for potential confounders, and because of the homogeneity of the study population with regard to occupation, substantial confounding by factors related to socioeconomic status is unlikely. In our study, nutrient and fiber intakes were assessed 2 years before the assessment of breakfast consumption, potentially leading to incomplete adjustment for these variables. However, dietary intakes are intermediates rather than confounders of the association between breakfast and weight gain, and the analysis without adjustment for dietary variables best reflects the full effect of breakfast consumption. Third, we only had information about breakfast consumption in 1992 and were, therefore, not able to take possible changes in breakfast consumption during follow-up into account. However, in this population of middle-aged and older men, dietary patterns tend to be stable over time (33). Moreover, changes in breakfast consumption during follow-up would have weakened rather than strengthened our results. Indeed, when we took into account factors that could lead to changes in dietary habits by excluding smokers and men who developed chronic diseases during follow-up in secondary analyses, associations were stronger or essentially unchanged. In conclusion, our study suggests that the consumption of breakfast may modestly lower the risk of weight gain in middle-aged and older men. The observation of a stronger association in men who were not overweight at baseline suggests that breakfast consumption may particularly contribute to the prevention of overweight. An effect of breakfast consumption on reduced weight gain would have important public health implications, and further research in cohort and experimental studies is warranted to verify our findings. Acknowledgments We thank Walter C. Willet for suggestions. The Health Professionals Follow-up Study is supported by NIH Grants CA and P30 DK A.A.W.A.v.d.H. is supported by the Netherlands Heart Foundation and by the Dutch Diabetes Foundation. References 1. Mokdad AH, Ford ES, Bowman BA, et al. Prevalence of obesity, diabetes, and obesity-related health risk factors, JAMA. 2003;289: Siega-Riz AM, Popkin BM, Carson T. Trends in breakfast consumption for children in the United States from Am J Clin Nutr. 1998;67:748 56S. 3. Haines PS, Guilkey DK, Popkin BM. Trends in breakfast consumption of US adults between 1965 and J Am Diet Assoc. 1996;96: Morgan KJ, Zabik ME, Stampley GL. The role of breakfast in diet adequacy of the U.S. adult population. J Am Coll Nutr. 1986;5: Melanson KJ, Westerterp-Plantenga MS, Saris WH, Smith FJ, Campfield LA. Blood glucose patterns and appetite in time-blinded humans: carbohydrate versus fat. Am J Physiol. 1999;277:R Drummond S, Crombie N, Kirk T. A critique of the effects of snacking on body weight status. Eur J Clin Nutr. 1996;50: Ruxton CH, Kirk TR. Breakfast: a review of associations with measures of dietary intake, physiology and biochemistry. Br J Nutr. 1997;78: Cho S, Dietrich M, Brown CJ, Clark CA, Block G. The effect of breakfast type on total daily energy intake and body mass index: results from the Third National Health and Nutrition Examination Survey (NHANES III). J Am Coll Nutr. 2003;22: Koh-Banerjee P, Franz M, Sampson L, et al. Changes in whole-grain, bran, and cereal fiber consumption in relation to 8-y weight gain among men. Am J Clin Nutr. 2004;80: Ma Y, Bertone ER, Stanek EJ 3rd, et al. Association between eating patterns and obesity in a free-living US adult population. Am J Epidemiol. 2003;158: Song WO, Chun OK, Obayashi S, Cho S, Chung CE. Is consumption of breakfast associated with body mass index in US adults? J Am Diet Assoc. 2005;105: Ortega RM, Requejo AM, Lopez-Sobaler AM, et al. Difference in the breakfast habits of overweight/obese and normal weight schoolchildren. Int J Vitam Nutr Res. 1998;68: Barton BA, Eldridge AL, Thompson D, et al. The relationship of breakfast and cereal consumption to nutrient intake and body mass index: the National Heart, Lung, and Blood Institute Growth and Health Study. J Am Diet Assoc. 2005;105: Affenito SG, Thompson DR, Barton BA, et al. Breakfast consumption by African-American and white adolescent girls correlates positively with calcium and fiber intake and negatively with body mass index. J Am Diet Assoc. 2005;105: Berkey CS, Rockett HR, Gillman MW, Field AE, Colditz GA. Longitudinal study of skipping breakfast and weight change in adolescents. Int J Obes Relat Metab Disord. 2003; 27: Bazzano LA, Song Y, Bubes V, Good CK, Manson JE, Liu S. Dietary intake of whole and refined grain breakfast cereals and weight gain in men. Obes Res. 2005;13: Nooyens AC, Visscher TL, Schuit AJ, et al. Effects of retirement on lifestyle in relation to changes in weight and waist circumference in Dutch men: a prospective study. Public Health Nutr. 2005;8: OBESITY Vol. 15 No. 10 October 2007

7 18. Rimm EB, Giovannucci EL, Stampfer MJ, Colditz GA, Litin LB, Willett WC. Reproducibility and validity of an expanded self-administered semiquantitative food frequency questionnaire among male health professionals. Am J Epidemiol. 1992;135: Chasan-Taber S, Rimm EB, Stampfer MJ, et al. Reproducibility and validity of a self-administered physical activity questionnaire for male health professionals. Epidemiology. 1996;7: Rimm EB, Stampfer MJ, Colditz GA, Chute CG, Litin LB, Willett WC. Validity of self-reported waist and hip circumferences in men and women. Epidemiology. 1990;1: Summerbell CD, Moody RC, Shanks J, Stock MJ, Geissler C. Relationship between feeding pattern and body mass index in 220 free-living people in four age groups. Eur J Clin Nutr. 1996;50: Jenkins DJ, Wolever TM, Vuksan V, et al. Nibbling versus gorging: metabolic advantages of increased meal frequency. N Engl J Med. 1989;321: Farshchi HR, Taylor MA, Macdonald IA. Deleterious effects of omitting breakfast on insulin sensitivity and fasting lipid profiles in healthy lean women. Am J Clin Nutr. 2005; 81: Cummings DE, Purnell JQ, Frayo RS, Schmidova K, Wisse BE, Weigle DS. A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes. 2001;50: Boyle PJ, Shah SD, Cryer PE. Insulin, glucagon, and catecholamines in prevention of hypoglycemia during fasting. Am J Physiol. 1989;256:E Nakazato M, Murakami N, Date Y, et al. A role for ghrelin in the central regulation of feeding. Nature. 2001;409: Wren AM, Seal LJ, Cohen MA, et al. Ghrelin enhances appetite and increases food intake in humans. J Clin Endocrinol Metab. 2001;86: Schwartz MW, Porte D, Jr. Diabetes, obesity, and the brain. Science. 2005;307: Horton TJ, Hill JO. Prolonged fasting significantly changes nutrient oxidation and glucose tolerance after a normal mixed meal. J Appl Physiol. 2001;90: Siega-Riz AM, Popkin BM. The effect of ethnicity on the benefits of ready-to-eat cereal consumption at breakfast. Nutr Food Sci. 1998;28: Siega-Riz AM, Popkin BM, Carson TA. Differences in food patterns at breakfast by sociodemographic characteristics among a nationally representative sample of adults in the U.S. Am J Prev Med. 2000;30: Cohen B, Evers S, Manske S, Bercovitz K, Edward HG. Smoking, physical activity and breakfast consumption among secondary school students in a southwestern Ontario community. Can J Public Health. 2003;94: van Dam RM, Rimm EB, Willett WC, Stampfer MJ, Hu FB. Dietary patterns and risk for type 2 diabetes in U.S. men. Ann Intern Med. 2002;136: OBESITY Vol. 15 No. 10 October