After Andrew telling us about how we can measure and define obesity,
let's have a little look at the physiology behind it.
How did we get obese in the first place?
First thing to recognise that obesity is a chronic condition,
but it's not just one single disease.
Every obese person is different and there are many types of obesity.
People differ in the distribution of their fat.
For example, you may hear people described as apples or pears;
pears having greater weight around the bottom and thighs,
and apples having greater weight around the trunk and midsection.
It's the apple shape that's particularly associated with
poor health and with metabolic complications like diabetes.
That's because the apple shape usually indicates that there is fat inside the body,
not just in a layer under the skin,
but right inside the abdomen and inside the organs.
The other thing to think about is when obesity starts.
There are some people who are obese from early childhood,
even babyhood, and they tend to remain obese throughout their lives.
But many of us don't become obese until the teenage years,
or after child birth, or later in life.
Then, there's a third set of people with
obesity that have obesity secondary to another condition,
for example, a thyroid disease or Cushing's syndrome.
I'm a geneticist and I'm really interested in
the interplay of genes and the environment in causing obesity.
We need to think about the different causes of obesity in different people.
There are some people who may have mostly environmental causes of their obesity.
They maybe, don't know about nutrition,
maybe they live in a poor food environment,
they have a lot of deprivation and they don't
know how to control their environmental stimuli.
They might have a relatively small contribution of genes to their condition.
However, there are other types of obesity that we'll be hearing about later in
the course that are caused by genes almost entirely.
We have single gene
recessive and dominant forms of obesity that are passed down through families,
just like other inherited diseases, like thalassemia or cystic fibrosis.