Cardiovascular diseases caused by obesity
The following statements highlight the prevalence of heart diseases in obese individuals:
- There are 400 million adults worldwide who are obese and one billion who are overweight. Children are getting fatter too. Worldwide, 17.6 million children under five years of age are estimated to be overweight.
- As one get fatter, one’s risk of developing Type 2 diabetes and hypertension rises steeply. Statistics show that 21% of ischemic heart disease is attributable to a BMI above 21.
- Even when there are no adverse effects of the known risk factors, obesity by itself increases risk of heart diseases. Fat, especially intra-abdominal fat, affects the blood pressure and is an important risk factor of cardiovascular disease.
The most common method of measuring the obesity is BMI (Body Mass Index) which is calculated by dividing body weight (kilograms) by height (meters) squared. A BMI of 18.5 to 24.9 is considered normal whereas a BMI of 25 to 29.9 is considered over-weight. A person having a BMI of 30 or more is considered obese.
BMI does not distinguish between body fat and lean mass (everything other than fat – i.e., bone, muscle, water, etc.). Two people can have the same BMI but very different body fat content. Furthermore, this criterion may misclassify some people as obese who are not actually obese and miss a substantial proportion of people with excess body fat.
Another important method of measuring obesity is waist circumference and waist to hip ratio. A waist measurement of 35 inches or less in women and 40 inches or less in men is considered normal and more than this is unhealthy. A healthy waist to hip ratio for women is 0.8 or lower and for men is 0.7 or lower. A ratio of 0.85 + in women and 1.0 + in men is considered a high risk. Recently, newer techniques such as scans of visceral fat tissue are good measures of central obesity but they are costly and, therefore, cannot be used routinely.
Cardiovascular diseases in obesity –
Cardiovascular diseases caused by obesity are as follows:
Coronary artery disease – With the rise of BMI index, the risk of coronary heart diseases rises too. Coronary heart disease is a condition in which a waxy substance called plaque builds up inside the coronary arteries. These arteries supply oxygen-rich blood to your heart. Plaque can narrow or block the coronary arteries and reduce blood flow to the heart muscle. This can result in angina or heart attack.
Heart failure – This is a serious condition caused by obesity, in which the heart can’t pump enough blood to meet body’s needs. Left ventricular hypertrophy is common in obesity, which results in diastolic dysfunction. However, systemic hypertension may be absent in obesity. In such individuals, left ventricular volume is increased and increase in stroke volume and cardiac output as well as diastolic dysfunction are seen. These changes in the left ventricle are related to sudden death in obese patients. Changes in right heart also occur in obesity, which are related to pulmonary hypertension and right ventricular hypertrophy, dilatation and finally failure. So, right ventricular dysfunction can also occur as a consequence of left ventricular dysfunction and, therefore, the heart failure that develops is often biventricular.
High blood pressure - Obesity has a direct correlation with blood pressure. Higher BMI is found to be responsible for around 30% of the prevalence of high blood pressure. Hypertension is approximately three times more common in obese than normal weight persons. This relationship may be cause-and-effect in that when weight increases, so does blood pressure whereas when weight decreases, blood pressure falls.
Factors responsible for cardiovascular disease in obese -
Cardiovascular diseases in overweight and obese develop due to certain factors, which include atherosclerosis, high blood pressure, duration of excess body weight, location of fat, cholesterol profile and insulin resistance.
Atherosclerosis – There is enough evidence that obesity, primarily abdominal obesity, is a significant risk factor for symptomatic atherosclerosis. Atherosclerotic vascular changes in obesity are connected, in particular, with diet, shortage of exercise and physical activity. The clinically defined metabolic syndrome is the most prominent atherosclerotic risk factor based on adipose tissue dysfunction producing low grade inflammation and endothelial dysfunction.
Adipose tissue secretes pro-inflammatory adipokines which include TNF alpha, IL-6, leptin, plasminogen activator inhibitor-1 (PAI-1), angiotensinogen, resistin and C-reactive protein. Evidence is mounting to suggest that adipokines may directly influence endothelial function through their pro-inflammatory properties.
High blood pressure – The chances of having high blood pressure are greater if one is overweight or obese. Extra fat tissue in the body needs oxygen and nutrients in order to live, which requires the blood vessels to circulate more blood to the fat tissue. This increases the workload of the heart because it must pump more blood through additional blood vessels. More circulating blood also means more pressure on the artery walls. Higher pressure on the artery walls increases the blood pressure.
Insulin resistance - Obesity is the major cause of type 2 diabetes. This type of diabetes usually begins in adulthood but is now actually occurring in children. Obesity can cause resistance to insulin, the hormone that regulates blood sugar. When obesity causes insulin resistance, the blood sugar becomes elevated. Even moderate obesity dramatically increases the risk of diabetes.
Dyslipidemia – Dyslipidemia related to obesity is primarily characterized by increased triglycerides, decreased HDL levels and abnormal LDL composition. Dyslipidemia plays a major role in the development of atherosclerosis and CVD in obese individuals. All of the components of the dyslipidemia, including higher triglycerides, decreased HDL levels, and increased small, dense LDL particles, have been shown to cause atherosclerosis. All these lipid abnormalities are typical features of the metabolic syndrome. An important link between obesity, the metabolic syndrome and dyslipidemia seems to be the development of insulin resistance.
Abdominal obesity – Individuals with excess abdominal fat have a greater risk of heart disease than individuals with a similar BMI, who carry the fat in other areas of the body. Excess fat around the waist promotes inflammation and raises the risk of heart disease. It is not fully understand what the link between obesity and heart disease is but researchers suggest that inflammatory proteins produced by fat itself may play a role. The inflammatory proteins slash the levels of inflammation fighting proteins. Higher levels of the inflammatory proteins are linked to increased levels of blood sugar -- a sign of insulin resistance.
Duration of excess body weight – It has been found that longer duration of obesity is associated with sub-clinical coronary heart disease and its progression through middle age, independent of degree of adiposity. Therefore, preventing or delaying the onset of obesity at younger age may lower the risk of developing the atherosclerosis through middle age.
Prevention of obesity-
Prevention or reduction of obesity is the only way to avoid the development of cardiovascular diseases caused by it. Overweight or obese individual can benefit from healthy diet and adequate physical activity at any age. But one should keep a realistic goal of fat reduction.
Exercise – Exercise is an important part of any weight loss program and it should become a regular and permanent part of the lifestyle. You may need at least 60 minutes of moderate exercise a day to lose weight and prevent weight gain. Moderate aerobic exercise is generally defined as requiring the energy it takes to walk 2 miles in 30 minutes. Walking is a great way for almost everyone to increase the amount of time they exercise. Using a pedometer can be motivating. A pedometer is a device that attaches to the clothing and tracks how many steps one take in a day. A good goal is to work up to 10,000 steps a day (5 miles). If your healthcare provider agrees, try increasing your steps each week by 500 a day until you reach 10,000 steps a day. It helps to lose and prevent weight gain effectively, if one incorporates weight training (strengthening exercise) and stretching exercises in the regular exercise program.
Diet – We will need to reduce daily calorie intake in order to lose weight, which means eating and drinking less and making healthier food choices. A 1,200-calorie-a-day diet may be just what is required for those who need to lose 20 or 30 pounds. But if you're trying to lose 100 pounds or more, you need more calories just to survive.
One should enjoy plenty of vegetable and fruits, whole grains, lean meats and poultry, fish, eggs, and nuts. One should also take milk, yogurt, and cheese mostly with reduced fat but, at the same time, limit intake of foods containing saturated fats, added salt, added sugar and alcohol.
One should avoid fad diets that recommend unsafe practices such as fasting (going without food for long periods of time) or cutting out entire food groups such as meat, fish, wheat or dairy products. These are not sustainable, can make you feel ill, and may cause unpleasant side effects such as bad breath, diarrhoea and headaches.
Stress – Stress management is also important for the reduction of obesity as the stress plays a very significant role in increasing weight.
Globally, there is an upwardly increasing trend of development of overweight and obesity in individuals. This predicts that the incidence of cardiovascular diseases will increase sharply unless adequate preventive measures are taken to reduce overweight and obesity by the individuals.
The factors responsible for the development of cardiovascular diseases in obese include atherosclerosis, high blood pressure, diabetes, dyslipidemia and location and duration of excess fat.