Diet, physical activity, childhood obesity and risk of cardiovascular disease

Diet, physical activity, childhood obesity and risk of cardiovascular disease

International Congress Series 1262 (2004) 176 – 179 www.ics-elsevier.com Diet, physical activity, childhood obesity and risk of cardiovascular disea...

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International Congress Series 1262 (2004) 176 – 179

www.ics-elsevier.com

Diet, physical activity, childhood obesity and risk of cardiovascular disease Youfa Wang * Department of Human Nutrition, University of Illinois at Chicago, 1919 W. Taylor St., Chicago, IL 60612, USA

Abstract. Eating and physical activity (PA) patterns and obesity in childhood have many long-term effects on the risk of cardiovascular disease (CVD). Two-thirds of premature deaths in the US are due to poor nutrition, lack of PA and tobacco use. Obesity, a result of excess energy intake and inadequate PA, is an indicator of unhealthy lifestyles. Currently, over one-third of American children are overweight. Obesity in childhood is associated with dyslipidaemia, elevated blood pressure, and increased future CVD morbidity and mortality. Healthy eating and PA are essential for good health. National representative data show that unhealthy eating and insufficient PA is a serious problem among American children. Efforts should be made to help young people to develop healthy lifestyles at early age. D 2004 Elsevier B.V. All rights reserved. Keywords: Child; Lifestyle; Diet; Obesity; Cardiovascular disease

1. Introduction Lifestyles such as eating and physical activity (PA) patterns and obesity in childhood have a long-term effect on risk of cardiovascular disease (CVD). Poor diet and inadequate PA together account for at least 300,000 deaths in the US annually and are second only to tobacco use as the most prominent identifiable contributor to premature death [1]. Obesity, a result of prolonged positive energy balance due to excess energy intake and inadequate PA, is an indicator of unhealthy lifestyles. Currently two-thirds of American adults and over one-third American children are overweight [2,3]. CVD risk factors and atherosclerosis start in childhood [4,5]. In general, cardiovascular events do not happen until middle age. It is challenging to accurately measure people’s eating and PA, especially for children. As a result, it has been difficult to study the effects of lifestyles on the risk of CVD in young people. Much of the related research has focused mainly on examining the associations between lifestyles in childhood and the biological risk factors of CVD such as elevated blood pressure and unfavorable blood lipid profile.

* Tel.: +1-312-355-3382; fax: +1-312-413-0319. E-mail address: [email protected] (Y. Wang). 0531-5131/ D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ics.2003.12.018

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2. The influence of childhood lifestyles and obesity on risk of CVD 2.1. Eating patterns and risk of CVD Healthy eating is critical for good health and numerous studies show that dietary factors such as intakes of dietary fat, cholesterol, sodium, and vegetable and fruit affect the risk of CVD. Diet-related risk factors for CVD include high blood cholesterol, high blood pressure and obesity. These risk factors can be reduced by choosing a healthy diet. It is widely believed that young people having unhealthy eating habits tend to maintain these habits as they age although related findings are inconclusive. Healthy eating with appropriate energy intake, low fat, and adequate vegetable and fruit consumption is essential for the prevention of chronic disease. 2.2. PA patterns and risk of CVD PA plays an essential role in promoting good health and preventing chronic diseases. Regular PA can help reduce the risk of CVD in the following ways: improve cardiorespiratory fitness; lowers both total cholesterol and triglycerides and increases HDL; lowers the risk of hypertension and obesity; and helps reduce blood pressure in hypertensive patients. However, findings from prospective studies conducted in young people are inconclusive. Twisk et al. [6] reviewed five cohort studies conducted in Europe and North America, and found that high physical fitness during adolescence seems to be predictive of a ‘healthy’ CVD risk profile, but not high PA. Errors in measuring PA and their small sample sizes are at least partly responsible for this lack of evidence. 2.3. Childhood obesity and risk of CVD Obesity serves as a good indicator of unhealthy lifestyles such as high-energy and highfat intake and lack of PA, since obesity is the consequence of a prolonged positive energy balance. Childhood obesity has a number of immediate, intermediate, and long-term health consequences such as dyslipidaemia, elevated blood pressure and hypertension, increased CVD morbidity and morbidity [7 –9]. 2.4. Possible pathways for the long-term effects of childhood lifestyles on risk of CVD The long-term impact may be due to both the direct and indirect effects of such factors on the cardiovascular system: (a) these factors have long-lasting effects; (b) clustering of risk factors. Young people who have these unfavorable factors may also have other risk factors such as smoking, social, economic and environmental stress, which may adversely affect health; (c) persistence (tracking) of these factors from childhood into adulthood. Dietary and PA habits developed during childhood are likely to become lifelong habits, and overweight children are likely to remain obese as adults. 2.5. Patterns and trends of children’s dietary intake, PA and obesity in North America 2.5.1. Eating patterns National survey data show that in general American children consume too much fat and sodium, but not adequate fruit, vegetables or calcium [10 – 12]. On average, they obtain

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Table 1 Trends in US adolescents’ food intake patterns 1977 – 1996

34% of calories from fat and 12% from saturated fat. More than 84% eat too much total fat (%E>30%) and more than 90% eat too much saturated fat (%E>10%). Their vegetable and fruit consumption is very low compared with the recommendations ( z 5 servings/day). Only one-fifth meets the recommendations; 51% eat less than one serving of fruit a day. Moreover, studies suggest increased consumption of soft drinks, snack foods and large portion size foods (Table 1). 2.5.2. Physical activity Compared with the recommendations, American children’s PA is far too inadequate. The 2001 US Youth Risk Behavior Surveillance System (YRBSS) data show that 31% do not participate in PA at recommended levels; 9.5% participated in no vigorous or moderate PA [10]. Another recent national survey of children aged 9 –13 years shows that 61.5% do not participate in any organized PA during non-school hours while 22.6% do not engage in any free-time PA. On average, American children spend over 4 h a day watching TV or videotapes, playing video games or using a computer. Most of this time (2.8 h) is spent watching TV; 17% watch >5 h of TV a day. 2.5.3. Childhood obesity National representative data show that the prevalence of overweight (>85th BMI percentile) among American children has more than doubled since the 1970s (increased from 15% in 1971– 1974 to 26% in 1988– 1994 and 30% in 1999 –2000), while the prevalence of obesity (>95th BMI percentile) has increased four-fold, from 4% to 15% [2]. Minority and low-SES groups are disproportionably affected. But the US is not alone; childhood obesity has become a global epidemic. Recently, we found that many countries have experienced the increase of obesity over the past two to three decades (Fig. 1). This may be due to the dramatic changes in young people’s lifestyles as a result of social– environmental changes in these countries and the influence of increasing culture exchange and global trade, for example, the westernization of diet in many developing countries. In conclusion, many biological risk factors of CVD start in childhood. Many factors acting together influence young people’s lifestyle. The increasing global obesity epidemic is of great concern as childhood obesity has many immediate and long-term health consequences. At present, our understanding of the long-term impacts of lifestyles and conditions (e.g., obesity) developed during childhood on one’s future health is still limited.

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Fig. 1. Trends in the prevalence (%) of childhood overweight in selected countries worldwide. Different classifications of childhood overweight were used in some studies, but were consistent within country over time. The trends presented were based on data collected over different survey periods, from 6 years to 3 decades.

Nevertheless, the development of effective programs and policies for helping young people to develop healthy eating and PA habits at young ages should be a priority for the prevention of chronic disease. References [1] J.M. McGinnis, W.H. Foege, Actual causes of death in the United States, JAMA 270 (1993) 2207 – 2212. [2] C.L. Ogden, K.M. Flegal, M.D. Carroll, C.L. Johnson, Prevalence and trends in overweight among US children and adolescents, 1999 – 2000, JAMA 288 (2002) 1728 – 1732. [3] K.M. Flegal, M.D. Carroll, C.L. Ogden, C.L. Johnson, Prevalence and trends in obesity among US adults, 1999 – 2000, JAMA 288 (2002) 1723 – 1727. [4] S.R. Daniels, Cardiovascular disease risk factors and atherosclerosis in children and adolescents, Curr. Atheroscler. Rep. 3 (2001) 479 – 485. [5] H.C. McGill, Childhood nutrition and adult cardiovascular disease, Nutr. Rev. 55 (1 Pt 2) (1997) S2 – S11. [6] J.W. Twisk, H.C. Kemper, W. van Mechelen, Prediction of cardiovascular disease risk factors later in life by physical activity and physical fitness in youth: general comments and conclusions, Int. J. Sports Med. 23 (Suppl. 1) (2002) S44 – S49. [7] W. Burniat, T.J. Cole, I. Lissau, E. Poskitt, Child and adolescent obesity: causes and consequences, Prevention and Management, Cambridge Univ. Press, New York, 2002. [8] A. Must, R.S. Strauss, Risks and consequences of childhood and adolescent obesity, Int. J. Obes. Relat. Metab. Disord. 23 (Suppl. 2) (1999) S2 – S11. [9] C. Power, J.K. Lake, T.J. Cole, Measurement and long-term health risks of child and adolescent fatness, Int. J. Obes. Relat. Metab. Disord. 21 (1997) 507 – 526. [10] CDC, Youth Risk Behavior Surveillance System (YRBSS), Information and Results, 2001, http:// www.cdc.gov. [11] L. Jahns, A.M. Siega-Riz, B.M. Popkin, The increasing prevalence of snacking among US children from 1977 to 1996, J. Pediatr. 138 (2001) 493 – 498. [12] S.J. Nielsen, A.M. Siega-Riz, B.M. Popkin, Trends in food locations and sources among adolescents and young adults, Prev. Med. 35 (2002) 107 – 113.