Smart Carbs, Unsmart Carbs

Do we have to diet to lose weight?

The short answer to the question of whether it is necessary to diet to lose weight is no. It is not only unnecessary to diet, but dieting is actually ineffective for most people. But before we go on, we need to be clear what we mean by dieting.

A little while ago I carried out a survey on 100 people. More than nine in every ten people defined dieting as eating much less food than usual or eating food that is significantly different from usual, or both. Again, around nine out of ten people agreed that what they regarded as dieting was unsustainable in the long term. Most regarded dieting as a short-term fix.

Almost nine out of ten people did not regard the minor changes that I describe in the next few chapters as dieting. So what are these minor changes. Before we go into them over the next few chapters, let’s have a look at the major nutrients in our diet and see how we might ‘tweak’ them to get the best out of them without actually ‘going on a diet'.

Finding the truth about carbs

‘All carbs are good'; ‘All carbs are bad.’ Which is right? Your answer will depend on whom you believe. If you are a fan of low- fat diets, such as Weight Watchers, you will believe that it is only fats in your diet that matter and that the carbohydrates – or ‘carbs’ — are completely unimportant. Watch your fat intake and the carbs will take care of themselves. But if you are a fan of high- protein / low—carbohydrate diets, such as the original Atkins (which I still find people wanting to follow) or the induction phase of the New Atkins Diet, the message you will have received loud and clear is that, provided you virtually eliminate all carbohydrates, the types of fats are unimportant. Eat as much artery-clogging fat as you like, you will still lose weight. So where does the truth lie? The answer is with neither — time for a short lesson in nutrition and biology.

The energy producers

Our bodies need three sources of fuel: fats, carbs and proteins. Carbs are the fuels the body prefers as a source of glucose energy. Protein is converted to glucose if carbs aren’t available. What about fat? This is the emergency fuel that is stored in case we starve. When food enters the stomach, special chemicals called enzymes break it down so that the fats, carbs and proteins are absorbed into the bloodstream as small molecules. In the case of carbs these molecules are glucose. Let’s look at what happens to carbs, or glucose, next. They meet a hormone: insulin. The job of insulin, which is secreted by the pancreas gland, is to push glucose into our cells, where it is converted to energy or stored as a larger chemical called glycogen. But that is not all that insulin does. One of its other important actions is to store fat.

Insulin can make us fat

When we eat carbs, the resultant glucose causes the release of insulin. The more glucose in our blood the more insulin we produce. And the more insulin we produce the more fat gets stored in our bodies — in other words, the fatter we get. And if we keep pushing insulin too much, eventually it can’t do its job of converting glucose to energy properly so we have to produce more insulin to do the job. This is called glucose intolerance. Our cells become resistant to insulin, which is why we then need higher and higher levels of it. The result? High levels of insulin create more and more fat in our bodies, so we put on weight. Eventually, insulin resistance reaches a level when we become diabetic. That is what a particular kind of diabetes, known as type—2 diabetes, is insulin resistance. Or, if it doesn’t result in diabetes, it can cause a condition known as the metabolic syndrome (once called syndrome X). This is a group of clinical features includes: high blood pressure; abdominal obesity (too much fat around the waist — the most dangerous place to store fat in terms of heart disease); glucose intolerance; and abnormal levels of blood fats (high triglycerides and low HDL or ‘good' cholesterol).

Now, up to this point, fans of low-carb diets have got it right. But from this point on they are completely wrong. You see, every carb is digested and absorbed at a different rate with different effects on blood levels of glucose; for example, white bread causes a rapid rise in blood glucose, whereas an apple causes a much lower rise. And, of course, the quicker the rise and the higher the level of blood glucose, the more insulin is produced. And the more rapid and higher the rise, the more rapid the subsequent fall in blood glucose.

The causes of hunger post-meal

Most of us have experienced the feeling of fullness immediately after eating a Chinese meal followed by hunger only two hours later. Why does this happen? Simply, the carbs in a Chinese meal, especially the white rice, cause rapid high levels of blood sugar, which satisfies hunger, followed by rapid falls, but this makes us feel hungry again. Look at what happens when we eat a meal that starts off perhaps with a small portion of pasta cooked al dente (tender but with a bite in the centre), followed by a main course of your favourite meat or fish with new potatoes and lots of green vegetables, followed by fruit salad (and, go on, have some custard too, if you like!). The amount of carbs might be the same, perhaps even higher, than in the Chinese meal, but the resulting blood glucose levels are much lower. Why? Because these kinds of carbs are digested and absorbed much more slowly, so we feel satisfied and we don’t feel ravenous again two hours later. Just as importantly, our insulin levels haven’t been pushed sky high. It's the rapid rises that are the problem.

The Glycemic Index - A way to measure carbs

All carbs, therefore, are different. Some cause rapid rises in blood glucose, whereas others cause only gentle rises. The rate at which a particular carb causes blood glucose to rise is called its glycemic index, or GI for short. A carb with a low Gl causes gentle blood glucose rises, whereas a carb with a high Gl causes steep rises.

This means that low-GI carbs cause only gentle insulin production, whereas high-GI carbs cause high insulin production. Later in this chapter you will find a list of many common carbs divided into low, medium and high Gl.

Incidentally, if you ever knew it, forget all that nonsense about ‘complex carbohydrates’, such as potatoes, being better for your blood glucose than ‘simple carbohydrates’, such as white flour.

That was based on pseudo—science, which has been completely disproved. The chemical structure of a carb is no pointer to what it does to your blood glucose. The only way to find out, and the way researchers have discovered the GI values of carbs, is by laboriously feeding volunteers different carb foods and then measuring their blood glucose responses over a period of several hours. That is why the GI values are not yet available for every food, but we have enough information to work out a healthy and effective weight-loss diet.

- Dr Michael Spira, author of ‘The 12 Minute Weight Loss Plan’