Why eating low fat doesn't help you slim

For many years it has been claimed that low fat foods are the way forward when it comes to the obesity 'epidemic' that we are facing. If that is the case, then why is it that the more low fat foods we seem to consume, the greater the epidemic?

Well the news is out - low fat doesn't help you slim and can actually make you fatter

Let me explain by way of an example. Take milk for instance. Let's assume that milk is 50% fat and 50% lactose (it isn't but this is only an example). Lactose is milk sugar and is converted to glucose by the digestive system so it can be used by the body. Sugars are digested quickly. If you have a sudden influx of sugar (any type, including lactose, not just the white stuff we put in cakes etc), that sends signals to your body to produce more insulin. Insulin is the hormone that mops up excess sugar in the blood. Usually, it stores it in the liver as glycogen. Glycogen is used by the body to give you energy. If there is too much (your glycogen store cupboard is full), or if the insulin cannot process the sugar quickly enough (like after you scoff a chocolate bar or two), then it stores the excess as fat, usually laying it down around your midriff.

The problem then is, your body uses the glycogen first. It has to convert the stored fat to glucose again before it can use that, so it uses the glycogen. When your glycogen stores are depleted, rather than converting the fat, if you have continued to each foods that readily convert into glucose, your stores of glycogen will be replenished from this. The fat therefore, stays where it is - around your middle.

Fat on the other hand, is digested slowly. It does not cause your insulin to spike, because there is no sudden rush of glucose in the blood stream. If you eat a food that contains both fat and sugars, then your body digests these together and the sugar is digested slowly along with the fat.

Are you beginning to get the picture? Going back to the example of milk - if, as I said, milk contains 50% fat and 50% sugar (lactose), that is a ratio of 1:1. Take out half the fat, but keeping the volume of liquid the same, you are now going to have 25% fat and 75% lactose, which is a ratio of 1:3. You have three times as much sugar (lactose) as you have fat. So the milk is digested more quickly, the glucose in your blood spikes, your insulin also spikes and mops up the sugar, causing layers of fat to be laid down, because there is too much for your glycogen store room.

This is a simplistic explanation and milk doesn't actually come neatly packaged as 50% fat and 50% lactose. But it serves as a picture of what is actually going on when you remove fat from your diet. Fat gives energy, but it does so slowly and over a longer period; sugar gives energy and does so quickly, but it is short lived.

Have you ever wondered why you feel tired shortly after eating a chocolate bar that is supposed to give you extra energy? Well, it's because the insulin has removed the sugar from your blood because your body does not function well with too much sugar in the blood stream.

And as an aside, low fat foods are also partly responsible for the increase in type 2 diabetes, caused by insulin resistance; and could be a factor in the increase in milk allergies too, but that's another story