Obesity is a strong risk factor not only in the development of heart disease, but also in the development of risk factors such as high blood pressure and diabetes. It is measured in terms of body mass index, and a BMI over 28 being defined as ‘obese’ for the Indian population group.
What is the definition of obesity?
There are 2 ways to define obesity. The commonly used way is to use the body mass index, which takes into consideration the weight of the individual and their height. The normal healthy BMI is around 23, and anything above that is considered ‘overweight’.
However, there is one main drawback of body mass index – it does not take into consideration how much body fat the person has.
For example, a body builder will be quite heavy mostly due to muscle weight and not due to body fat. It is therefore not uncommon for a person of average height who has large muscles to have a high BMI. This does not mean that he/she is obese.
A better way to define obesity is to use a parameter called ‘waist:hip ratio’. This is the ratio of a person’s waist measurement to their hips. It is now recognised from studies that the waist:hip ratio is a better marker of obesity, and can predict the chances of developing heart disease and other illnesses in the future along with mortality (Larsson, 1984).
The link between obesity and heart disease
As previously mentioned, the obesity is not only linked to the development of heart disease, but also to the various risk factors as well. It is the increased incidence of these risk factors (hypertension, diabetes and high cholesterol) that in fact leads to heart disease in obese patients.
1. Coronary artery disease
The increased levels of body fat in obesity means higher levels of fat circulating in the blood stream.
Circulating fat and cholesterol is responsible in the development of atherosclerosis. Atherosclerosis is a condition where fat deposits on the walls of the blood vessels, leading to their narrowing. A narrowed blood vessel does not allow sufficient blood to flow through it during times of need.
When atherosclerosis affects the coronary arteries, it can lead to reduced blood supply to the heart muscle. This can lead to heart attacks and chest pain (angina). Obesity is now considered an independent predictor of coronary artery disease.
In addition, obesity can cause heart failure as well.
2. High blood pressure
There is a direct link between high body weight and high blood pressure. Clinical research has shown that having a high body weight can increase the retention of sodium in the body – a direct cause for blood pressure to rise. In addition, being obese can stimulate the release of certain hormones which are responsible in the development of hypertension.
Individuals who have a normal BMI have a low chance of developing high blood pressure. Studies conducted in the western world have shown that those who have a BMI of <25 (considered normal for the western population) have a 15% risk of developing hypertension, as opposed to 38% (women) and 42% (men) if the BMI is > 30 (Brown, 2000).
References
1.Larsson, B., et al. “Abdominal adipose tissue distribution, obesity, and risk of cardiovascular disease and death: 13 year follow up of participants in the study of men born in 1913.” British medical journal (Clinical Research ed.) 288.6428 (1984): 1401-1404.
2.Brown, Clarice D., et al. “Body mass index and the prevalence of hypertension and dyslipidemia.” Obesity research 8.9 (2000): 605-619.