Obesity

Hello. I’m Dr. Oonagh Markey. I would like to tell you about obesity. Obesity is defined by the World Health Organisation as an excessive or an abnormal accumulation of body fat, which can present a risk to health. Obesity is a major modifiable risk factor for cardiovascular disease. Obese individuals tend to have higher blood pressure, higher cholesterol, as well as higher triglycerides. These are the fats found circulating in your bloodstream. 1 in 4 adults in the UK are currently classified as obese. Unfortunately, children are not escaping this obesity epidemic. Did you know that childhood obesity is one of the greatest health burdens that we are facing in the 21st century?

In England, it is believed that 1 in 4 children aged 2 to 15 years are either overweight or obese. The worrying thing about childhood obesity is that these children are at increased risk of premature death during adulthood. And it is believed that they carry forward cardiovascular damage with them into adulthood. So how does obesity occur? Obesity is caused by an energy imbalance. So over a prolonged period of time, if you have more energy going in to your food and drink consumption than going out to the body’s metabolic activity, as well as physical activity, you are likely to put on weight and this could lead to obesity. Obesity is caused by a complex web of factors.

Both lifestyle and behaviour choices can contribute to weight status. Physical inactivity, sedentary behaviour, and poor eating choices can all contribute to obesity. In addition to this, some genetic components can make some individuals more susceptible to obesity. How do we measure obesity? There are numerous different ways that we can look at obesity. However, I’m going to focus on body mass index and waist circumference. These are useful tools for looking at obesity at a population level. I’ll start with body mass index, or BMI for short. As your body mass index increases so too does your risk of heart disease. BMI is a very crude measure of adiposity. However, it’s a useful way of looking at obesity at a population level.

It is calculated as a person’s weight in kilogrammes divided by the square of their height in metres. Although there are different BMI cut off points in place for different ethnicities, it is generally believed that a BMI of 25 plus means that a person is overweight while a BMI of 30 plus indicates that someone is obese. Body mass index does have its downfalls. It does not discriminate between fat and muscle mass. And therefore, it needs to be used with caution in some populations. For example, those of athletic build or athletes because they will have a high proportion of muscle mass. Another downfall of BMI is that it doesn’t take fat distribution into account.

And this is also an important feature, which needs to be focused on for a disease risk. So what do I mean by fat distribution? Well, depending on where people store their excess fast, they can be defined as either having an apple shape or pear-shaped body. Apple-shaped individuals tend to store their excess fat around their middle. Some of this fat is called visceral fat. So it’s the fat that lines the internal organs of the body, such as the pancreas and the liver. It is the visceral fat that is linked to increased risk of cardiovascular disease. So it’s not the subcutaneous fat (the wobbly fat) that you might be able to grab in your hands.

The other type of body shape is the pear-shaped individual. So these people tend to have a smaller waist and larger hips and thighs. And this shape is believed by many to be cardioprotective or beneficial to heart health. Waist circumference is one measure for looking at the distribution of weight around your middle. So if you have a large proportion of fat around your middle, you might be centrally obese. For men, if they have a waist circumference of 94 centimetres or greater, they are at an increased risk of cardiovascular disease. A waist circumference of 80 centimetres or greater in females suggests that that female might be at risk of heart disease.

Like for a body mass index, there are different waist circumference thresholds in place for different ethnicities, such as Asian populations. Although not all of the fat that is found around your waist is visceral fat, waist circumference has been found to be a good indicator of disease risk. And some guidelines, such as those in place by the World Health Organisation suggests that it might be good to combine both body mass index and waist circumference to give a more accurate description of disease risk.