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Public Health Aspects of Overnutrition.pptx

This presentation explains the public health aspects of overnutrition, including causes of obesity, dietary factors, lifestyle influences, health risks, and strategies for prevention and control from a public health nutrition perspective.

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Public Health Aspects of Overnutrition Aktarafun Zannat Assistant Professor (Food and Nutrition) Govt. College of Applied Human Science, Azimpur, Dhaka
Contents • Principles of anthropometric classification of overweight and abdominal fatness • Prevalence of and trends in overweight • Macronutrients, excess energy intake and overweight • Obesity as a determinant of mortality and morbidity
Introduction • Overnutrition is a form of malnutrition (imbalanced nutrition) arising from excessive intake of nutrients, leading to accumulation of body fat that impairs health (i.e., overweight/obesity)- https://pmc.ncbi.nlm.nih.gov/articles/PMC6755771/#sec1-1 • Overnutrition refers mainly to excessive intake of energy, especially from sugar and fat, and its effects are commonly assessed through overweight and obesity. • Since direct measurement of body fat is difficult in public health settings, crude anthropometric measures are usually used. • Obesity is defined as excess fat stored in adipose tissue, while advanced methods like bioimpedance and DEXA can measure body composition but are not routinely measured.
Principles of anthropometric classification of overweight and abdominal fatness • Anthropometric classification of overweight and abdominal fatness mainly relies on BMI and waist-related measurements to identify health risk. • A healthy BMI range is generally associated with the lower mortality, while overweight and obesity increase the risk of morbidity and other chronic diseases. • However, the health significance of a given BMI may differ across populations, with some groups, such as Asians, facing higher risk at the same BMI level. • Measures like waist–hip ratio and waist circumference are also important because they reflect fat distribution, especially abdominal fatness. • Among these, waist circumference is often considered a more practical indicator of central obesity, though the exact cut-off values and action levels remain under debate.
Prevalence of and trends in overweight • Overweight and obesity have shown a clear rising trend worldwide across both men and women in almost every region. • This increase is seen not only in highly affected areas but also in countries with previously low obesity levels, such as Japan and China, showing that obesity is now a truly global public health problem. • The trend is also evident among children and adolescents, with marked increases reported in Europe and the United States over time. • Overall, obesity is no longer limited to affluent Western societies, but affects both industrialized and developing populations alike.
Macronutrients, excess energy intake and overweight  Fat Intake • Obesity develops when energy intake exceeds energy expenditure, and high fat intake can contribute because fat is very energy-dense, providing much more energy per gram than carbohydrate or protein. • Diets rich in fat are often tasty and energy dense, which may encourage passive overconsumption and gradual weight gain. • Replacing saturated fat with unsaturated fat may improve blood lipid profile and cardiovascular risk, while replacing some dietary fat with carbohydrate-rich, fibre-rich foods, together with regular physical activity, is more likely to support weight reduction.
Macronutrients, excess energy intake and overweight Carbohydrate type (sugar, glycemic index and fiber)  Sugar in foods: • Sugar, glycemic index, and fiber are closely related dietary factors, but sugar in foods has a complex relationship with body weight. • Although higher carbohydrate intake may seem protective against weight gain because it often replaces fat, this does not always hold true when the carbohydrate comes largely from sugar. • Large population studies show that people with higher total energy intake often consume more sugar, and while some studies have found an inverse relationship between sugar as a percentage of energy and BMI, this should not be interpreted as advice to increase sugar intake.
Macronutrients, excess energy intake and overweight • Evidence is especially stronger for sugar-sweetened soft drinks, which consistently appear to increase total energy intake and promote weight gain, particularly among children.  Glycemic index and dietary fiber: • Different carbohydrate-containing foods can affect hunger and satiety in different ways depending on their glycemic index and fiber content. Lower-GI foods may produce greater fullness after meals, possibly through effects on blood glucose, insulin response, and appetite-related hormones such as cholecystokinin. • At the same time, higher dietary fiber intake is generally associated with lower BMI and protection against weight gain.
Macronutrients, excess energy intake and overweight • Fiber may support energy balance by lowering energy density, slowing gastric emptying, improving satiety, moderating post-meal blood glucose, and influencing fermentation in the colon. • Overall, the evidence is suggestive for low-GI diets and convincing for a protective role of high fiber intake against weight gain.  Alcohol: • Alcohol is an energy-dense nutrient and may contribute to obesity because it is oxidized before other fuels, potentially reducing fat oxidation and encouraging fat storage. • However, the relationship between alcohol and body weight remains unclear, as epidemiological studies have shown mixed results, with some reporting positive, negative, or no association with BMI.
Obesity as a determinant of mortality and morbidity  Obesity and mortality: • The relationship between obesity and mortality has been studied for decades, and BMI is often described as having a U- shaped or J-shaped association with all-cause mortality. • However, this relationship can be distorted by important confounding factors such as smoking, pre-existing illness, and inappropriate adjustment for intermediate risk factors like blood pressure, blood lipids, and diabetes. • BMI also has limitations because it does not distinguish clearly between fat mass and lean body mass, especially in older adults. • Socioeconomic status, ethnicity, physical inactivity, and reduced fitness further complicate the interpretation of how obesity influences mortality.
Obesity as a determinant of mortality and morbidity  Obesity and cardiovascular disease: • Obesity, particularly abdominal obesity, is a major risk factor for cardiovascular disease because it is associated with high blood pressure, unfavourable lipid profile, low HDL-cholesterol, and raised triacylglycerol levels. • It also acts as an independent risk factor, meaning that its harmful effect is not explained only by other metabolic abnormalities. • Studies have shown that people with higher BMI have markedly greater risk of coronary heart disease and stroke, and weight reduction can improve several cardiovascular risk factors. • Overall, maintaining a healthy body weight could substantially reduce the burden of coronary events, stroke, and heart failure.
Obesity as a determinant of mortality and morbidity  Obesity and type 2 diabetes mellitus: • Obesity, especially abdominal obesity, is considered the strongest risk factor for the development of type 2 diabetes and is one of the most costly public health consequences of excess body weight. • It is closely linked with the metabolic syndrome, which includes high glucose, hypertension, raised triacylglycerols, and low HDL- cholesterol. • Research shows that the risk of type 2 diabetes rises sharply even at moderately increased BMI, and in some ethnic groups, especially certain Asian populations, this risk begins at relatively low BMI levels. • Encouragingly, moderate lifestyle change and small weight loss in high-risk individuals can reduce the risk of developing type 2 diabetes by as much as 60%.
Obesity as a determinant of mortality and morbidity • Obesity and cancer: • There is substantial evidence that avoiding weight gain may help prevent several cancers, particularly postmenopausal breast cancer, endometrial cancer, kidney cancer, and esophageal adenocarcinoma. • Obesity may increase cancer risk through hormonal and metabolic changes, including increased estrogen production in adipose tissue and greater availability of insulin-like growth factors that can support tumor growth. • In postmenopausal women, excess abdominal fat may raise breast cancer risk because adipose tissue becomes a major source of circulating estrogen. • Obesity may also worsen cancer outcomes indirectly by making tumor detection more difficult and reducing participation in screening programs.
Obesity as a determinant of mortality and morbidity  Obesity and musculoskeletal disorders: • Obesity is one of the most important preventable risk factors for osteoarthritis, especially in the knee and hip joints, and this contributes greatly to disability. • The main explanation is the increased mechanical pressure placed on joints in overweight individuals, although metabolic factors may also play a role. • Obesity has also been linked to hand osteoarthritis, suggesting that the effect is not purely mechanical. • Associations with low back pain, chronic neck pain, and herniated lumbar disc have also been suggested, though the evidence for these is weaker and often based on cross- sectional studies.
Obesity as a determinant of mortality and morbidity  Obesity and respiratory disorders: • Obesity is strongly associated with respiratory problems such as shortness of breath, sleep apnea, and related psychosocial difficulties. • Excess body fat can impair lung function and increase the likelihood of sleep-disordered breathing, while body fat distribution also matters, with neck girth showing a particularly strong association with respiratory risk. • Obese individuals are more likely to experience hypoventilation during sleep, nocturnal hypoxia, and severe daytime sleepiness. • As a result, obesity-related respiratory disorders are now recognized as an important public health concern.
Obesity as a determinant of mortality and morbidity  Obesity and work disability: • Obesity is strongly linked to work disability, mobility problems, poorer quality of life, and unhealthy ageing. • Population studies from countries such as Finland and Sweden show that obese people are more likely to receive disability pensions and take more sick leave than those with lower BMI. • The risk of work disability appears to rise progressively as BMI increases in both men and women. This means that the impact of obesity extends beyond disease and mortality to major social and economic consequences.
Summary of the impact of obesity on public health: • Obesity has wide-ranging effects on public health and is linked not only to mortality and cancer but even more strongly to type 2 diabetes, cardiovascular disease, musculoskeletal disorders, sleep apnea, and work disability. • Its economic burden is also considerable, accounting for a notable share of healthcare costs in both the USA and Europe. Because obesity contributes more to morbidity and disability than to mortality alone, its long-term burden is likely to increase further. • Even modest weight loss can produce meaningful health benefits by reducing years lived with hypertension and diabetes and by slightly improving life expectancy.
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Ref: Lobstein, T., & Lang, T. (2004). Public health aspects of overnutrition. In M. J. Gibney, B. M. Margetts, J. M. Kearney, & L. Arab (Eds.), Public Health Nutrition. Oxford: Blackwell Publishing.