The cause of obesity is multifactorial – this means there are numerous factors acting together. It is first and foremost a metabolic disease in that too much glucose is converted into adipose tissue. There is undoubtedly a genetic predisposition to obesity as demonstrated by studies on identical twins and also in children adopted by adults other than their natural parents. But to blame your obesity on your parents is to dramatically side-step the truth which we will come on to shortly.
Another important determinant of the predisposition to developing obesity is the level of insulin that a foetus is exposed to in the uterus. A high level of circulating maternal insulin leads to similar levels in the child, which then potentially leads to the development of obesity in infancy through insulin resistance, running the significant risk of perpetuating it into adult life.
You have no choice other than to accept the genes you were given but since genetic factors are of relatively low importance you don’t need to get too hung up about them. Similarly, you had no control of your mother’s insulin when you were inside her. But the great news is that you can reverse any insulin resistance that she set you up with.
Now on to the important stuff. The food that we eat is fundamental in the onset and maintenance of obesity and there are three factors to consider – how much we eat, what sort of food we eat and when we eat. The first one is important but not as important as the second one. But what is absolutely critical is when we eat.
Conventional wisdom, that the individual is consuming too many calories and moving insufficiently, is absurdly over-simplistic. An excess itself of calories does not necessarily cause obesity simply because calories-in and calories-out are very dependent upon each other. The first thing that is observed if calories-in is increased is a concomitant increase in basal metabolic rate, effectively utilising most if not all of the consumed calories.
It is also important to take into consideration where these calories are coming from simply because the body handles and responds to the various macronutrients in different ways. So, a set number of calories from carbohydrates have a different effect to the same number of calories from protein and similarly with fat.
The one fact that is critical to the onset of obesity is insulin levels and the subsequent development of insulin resistance. Insulin is the hormone that is secreted by the pancreas in response to a rise in blood glucose.
Its actions are to push glucose into the cells for immediate use or, if not required, into the liver for storage as glycogen and at the same time into adipose tissue after first being converted into fatty acids and triglycerides (lipogenesis). A chronically raised blood insulin level, as seen with an uninterrupted intake of, in particular, carbohydrate will facilitate the continuous deposition of adipose tissue.
As discussed in the presentation entitled “Insulin”, the insulin response to the various macronutrients varies enormously, with carbohydrate producing the greatest response, followed by protein. Fat by contrast produces a very small insulin response – in fact almost negligible. So, a meal that is high in carbohydrate, which gets absorbed as glucose, produces a rapid rise in blood insulin which then falls relatively slowly. The blood glucose falls fairly quickly producing the sensation of hunger.
Insulin itself is responsible for increasing the hunger sensation so in effect the brain is hit from two different directions by the same process. The overall effect is to prompt the individual to eat another meal fairly soon after the first one. This once again is responsible for repeating the cycle of a fast rise in blood sugar followed by an equally fast rise in blood insulin and so the pattern is repeated.
One of the significant effects of a chronically raised insulin level in the blood is for the tissues to become resistant to insulin itself. In effect the cells sense that they are becoming saturated and the insulin receptors are down-regulated. This means that even more insulin is required to produce the same effect and so the feedback mechanism causes the pancreas to increase the output.
So again, a vicious circle is set up where by the individual is forced to take in more food, usually in the form of carbohydrate and this leads to the promotion of stored body fat and the inevitable development of obesity.
So, as you can see it’s not the quantity of food that’s important. It’s certainly a consideration. And it’s for this reason that the calorie-restricted diet, that concentrates almost exclusively on quantity, fails almost every time. Anyone who has been on a calorie-restricted diet will tell you this and all of the scientific studies confirm it.
However, if you address the important issue of the type of food you eat, in particular limiting dramatically your refined carbohydrate, and crucially when you eat, then you will prevent obesity happening in the first place but also successfully manage it if and when it happens.