It is important that anyone with a medical condition or who is pregnant should consult their doctor before starting a low carb or low GI diet (for instance, diabetics may find it reduces or even eliminates their need for insulin).
Are you doing a low carb diet? Is a low carb diet healthy? Well, if you're only eating steak, bacon, eggs and other proteins and fats, and not eating any salads or vegetables, then you're not doing a low carb diet, and no, your diet isn't healthy! To find out what low carb diets are really all about, please read on ...
Many people who have had little success in controlling their weight with low calorie, very low calorie and low fat diets have discovered that restricting carbohydrate is a far more effective method of both losing excess weight and keeping it off. They also report additional advantages: they eat more, the food they are allowed is more palatable, and they no longer suffer the hunger pangs, lack of energy, weakness, headaches, cravings and feelings of control and deprivation frequently experienced with calorie/fat restriction. A further plus with low carb diets is that there is generally no need to weigh foods or restrict portion sizes.
Low carb diets have been around for many decades but their popularity declined in the 70s, 80s and 90s due mainly to unsubstantiated concerns about their safety. However, research since then has shown these concerns to be scientifically groundless. In fact, better understanding of the science behind low carb diets and the link between high carbohydrate intake and obesity, heart disease and diabetes has led many researchers to believe that low carbing is actually more healthy than the low fat/high carb diet we are all currently advised to follow. An article which appeared in The New York Times on 7 July 2002 by journalist Gary Taubes, 'What if It's All Been a Big Fat Lie?' gives an excellent insight into this fascinating subject.
Since then Gary Taubes has published a book called 'Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control and Disease (called 'The Diet Delusion' in the UK). In this book Gary provides detailed scientific evidence demonstrating that weight loss is not simply a matter of eating fewer calories, that heart disease is not simply a matter of eating too much fat and that obesity, heart disease and diabetes are instead caused by the insulin-triggering high carbohydrate diet that has become our standard diet.
In similar fashion, UK doctor Malcolm Kendrick discussed the role of fats in the diet in his 22 November 2003 article 'Why the Atkins Diet is Healthy'. He explained how the belief that a diet high in saturated fat causes high cholesterol/lipids is wrong, and that the accepted truth that high cholesterol causes heart disease is incorrect in any case. He explains his views on the real cause of heart disease in a presentation to the BMA (British Medical Association) at their meeting in Leeds.
Dr John Briffa has written various books including 'Escape the Diet Trap', Zoe Harcombe has written 'The Obesity Epidemic - What Caused it? How Can We Stop It?' and countless others have published their own books on this theme of how the traditional weight loss advice of a low fat/low calorie diet and more exercise ignores the reality of how our bodies work and how concerns about low carb diets causing heart disease are not supported by the science.
Low carb diets are not however just about reducing carbs. The Atkins Diet in particular teaches the benefits of plenty of salads and vegetables, fruits if you can tolerate their sugar content and other unprocessed wholefoods such as pulses or legumes (peas, beans and lentils) and wholegrains. It also warns of the havoc that the hormones and other chemical additives and residues that we increasingly find in our food can play with our metabolic processes. Genuine low carb diets are not fad diets or quick weight-loss diets - they are a nutritionally and hormonally based way of eating which promotes improved health, prevents and treats diabetes (type 2), improves heart disease risk factors and produces weight loss in the up to 60 per cent of the population who are carbohydrate-sensitive.
Results of low carb diet trials published so far have shown that, contrary to popular belief, low carb diets such as Atkins are very effective and safe. These trials have also shown unexpectedly good improvement of risk factors for heart disease such as triglycerides, cholesterol and blood pressure. The consistency of these recent findings is causing more and more experts to question their long-held beliefs that to be healthy a diet must be low in fat. Here are some of the studies:
The Atkins Diet for epilepsy
'A modified Atkins Diet is an effective and well-tolerated therapy for intractable pediatric epilepsy.'
Kossoff, E.H., McGrogan, J.R., Bluml, R.M., Pillas, D.J., Ruberstein, J.E., Vining, E.P., 'A modified Atkins Diet is an effective and well-tolerated therapy for intractable pediatric epilepsy', Epilepsia, 2006, 47(2):421-424.
'The ketogenic diet is effective for treating seizures in children with epilepsy. The Atkins Diet can also induce a ketotic state, but has fewer protein and caloric restrictions, and has been used safely by millions of people worldwide for weight reduction. ... This provides preliminary evidence that the Atkins Diet may have a role as therapy for patients with medically resistant epilepsy.'
Kossoff, E.H., Krauss, G.L., McGrogan, J.R., Freeman, J.M., 'Efficacy of the Atkins diet as therapy for intractable epilepsy', NEUROLOGY, 2003;61:1789-1791.
'Only a decade ago the ketogenic diet was seen as a last resort; however, it has become more commonly used in academic centres throughout the world even early in the course of epilepsy. The Atkins diet is a recently used, less restrictive, therapy that also creates ketosis and can lower the number of seizures.'
Kossoff, E.H., 'More fat and fewer seizures: dietary therapies for epilepsy, THE LANCET Neurology, 2004, 3:415-20
Many more studies are being published all the time. Landmark studies demonstrating that the 'high fat diets cause heart disease' belief is indeed just a myth are now starting to appear in mainstream medical journals. An example is a recent paper entitled "Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease", which appeared in the highly respected American Journal of Clinical Nutrition. Its conclusion was "There is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of coronary heart disease or cardiovascular disease". Other studies appearing in equally well respected journals such as the New England Journal of Medicine have produced similar conclusions.
Pro-Atkins and low carb medical professionals
The increasing weight of evidence supporting the Atkins and other low carb diets has caused many medical professionals to rethink their previously negative stance.
As the evidence grows, more medical professionals are starting to become familiar with the Atkins Diet and other low carb diets. One example is Dr Sarah Brewer, who is a keen supporter of the Atkins Diet. Dr Brewer was a full time GP for five years and now works in nutritional medicine. She writes widely on complementary medicine and the sensible use of supplements, has written 40 popular self-help books and appears regularly on TV and radio. Dr Dee Dawson, medical director at North London's Rhodes Farm Clinic, which treats children with eating disorders, is also using the diet, saying: 'The diet is good for youngsters. I think the basis of Atkins is a good diet for children whose priority is to get weight off.' Dr John Briffa, a London-based medical doctor, author and speaker is another keen advocate of low carb diets, as is obesity researcher and nutritionist Zoe Harcombe.
The science behind low carb (and low GI / low GL) diets
Low carb (and low GI / low GL) diets are based largely on the science of blood sugar control mechanisms. A very simplified explanation of the process is as follows: carbohydrate foods (starches and sugars) are converted by digestion to a form of sugar called glucose. The rising levels in the blood trigger the pancreas to release the hormone insulin. It is the job of insulin to keep the blood sugar levels stable and trigger the process by which excess glucose is removed from the bloodstream and, if not needed for immediate energy, stored as fat.
This storage mechanism was extremely useful in mankind's hunter-gatherer days. It enabled early man to survive in between his irregular and unpredictable meals. Unfortunately, this storage mechanism is not so useful where food, and carbohydrate in particular, is constantly in abundance. Our bodies were not designed to be fuelled by the highly refined carbohydrate-dense foods such as white sugar and flour that are now the staple foods of the Western world. In time the process of evolution might result in a population genetically adapted to such a diet, but this would take millions of years, not the tens of years that such foods have been available to us in the quantities in which we consume them today.
The trick is to stop this constant production of insulin. Low carb diets attempt to do this by avoiding glucose surges ('spikes') in the blood. This can be achieved by restricting carbohydrate overall, and by preferring those carbohydrates which rank low on the glycemic scale (ie which cause less rapid rises in blood sugar).
The Atkins Diet is probably the most well known and widely used low/controlled carb diet, but other examples include Dr Richard Mackarness' Eat Fat and Grow Slim Diet, SugarBusters, the Carbohydrate Addict's Diet, Protein Power, The Paleolithic Diet, Neanderthin, the Zone, Life Without Bread, the Eskimo Diet, the Stone Age Diet, the Schwarzbein Principle, the Specific Carbohydrate Diet, the South Beach Diet, Fat Flush Plan and the Radiant Health Programme. Although many of these diets have appeared relatively recently, the Atkins Diet dates back to the seventies and Dr Mackarness' back to the fifties. However, the first true low carb diet was around long before that - the Banting Diet. Used by William Banting in 1862 to lose 50lb in less than a year, he was so delighted to have found a way to solve his weight problem that he published a pamphlet "Letter on Corpulence" in 1864 at his own expense.
The link between high carbohydrate intake and obesity, heart disease and diabetes
At best, constantly high insulin levels may make it difficult for the individual to lose or maintain weight. However, if the overproduction of insulin is allowed to continue, insulin resistance may develop, more and more needs to be produced to get the same effect, and ultimately the stressed pancreas may cease to produce enough insulin or give up altogether, producing full-blown diabetes. Not only that, but there is a growing body of evidence to support the belief that it is these constantly high levels of circulating insulin (and not dietary or blood levels of fat) that are the real culprits in creating the damage that results in cardiovascular disease, whether or not diabetes is present.
This certainly helps explain why, despite more people than ever following the official 'healthy eating' guidelines (low fat/high carb), the incidence of obesity, heart disease and Type 2 diabetes is rising alarmingly fast. The pity of it is that those who are in the early stages of insulin resistance and pre-diabetes are quite likely to be unaware of the fact, although clinicians such as Dr Atkins report that these conditions are reversible at this stage by simply avoiding the cause of the problem - a carbohydrate intake that the individual is unable to handle. The UK Government recently estimated there to be over 1 million undiagnosed Type 2 diabetics in the UK alone, so the number of those at risk of developing the condition in the future must be considerably higher than that. And as explained earlier, even if these individuals ultimately escape the diabetes, the increased risk of cardiovascular disease still remains.
In other words, evidence is growing that the real villain in obesity, heart disease and Type 2 diabetes may be high dietary intake of carbohydrate, not fat. If this is the case, then it means that for many of us, following the current official 'healthy eating' guidelines may be entirely the wrong way for us to be eating.
Syndrome X/metabolic syndrome, PCOS and acne
A low or controlled carbohydrate way of eating is also increasingly being seen as beneficial in a number of other insulin-related conditions, whether or not weight loss is the primary aim, which include Syndrome X (also called insulin resistance or Metabolic Syndrome) and PCOS (Polycystic Ovary Syndrome). Teenage acne is also now believed to be related to insulin levels by some dermatologists, who advocate a low carb diet as treatment.
Food allergy / food intolerance and candida
Low carb and low GI diets can also help where food allergies / food intolerances and candida (yeast overgrowth in the gut) are a factor in ill health. These conditions are increasingly considered by nutritional medicine practitioners to play an important role in inability to lose weight and other chronic problems ranging from headaches and indigestion to arthritis and irritable bowel syndrome. The literature demonstrates the largely unrecognised prevalence of these conditions and explains how they can be caused or fuelled by over-consumption of refined carbohydrates, leading amongst other effects to blood sugar/insulin imbalance and obesity.
The mainstream medical establishment, virtually untrained in nutritional and environmental medicine, remains to be convinced. However, this position is gradually changing since the launch of a new pioneering course by the University of Surrey to bring nutritional medicine into the mainstream of medical practice. Aimed at GPs, consultants, pharmacists and dieticians, the course offers Postgraduate Diploma and MSc qualifications in the use of nutritional methods to prevent and treat conditions such as food intolerance / allergy, cancer, diabetes and heart disease.
Dr Atkins and many other low carb diet authors acknowledge the existence of food intolerance / allergy and candida. They suggest they may be a reason why so many low carb dieters not only achieve weight loss but also find other health problems have improved or disappeared. Future research may confirm that these conditions are closely linked with the blood sugar / insulin regulation that is the underlying premise of low carb diets. What is for sure is that many low carb diets restrict or eliminate the foods, such as wheat and corn (maize), that are most often implicated in these problems. This and many other reasons for difficulty in losing weight are explained in "Why Can't I Lose Weight".
By cutting carbohydrate intake to an extremely low level, the body can be made to 'change gear' and start raiding its fat stores for energy (called lipolysis). Diets which aim for this change of gear are called 'lipolytic' or 'ketogenic'. However, the change of gear will only happen once the body has used up its other, more readily available energy stores. One way of telling whether this has happened is to test for ketones, which are excreted as a harmless byproduct of this fat breakdown. This is called being 'in ketosis'. (Ketosis is commonly confused with, but has nothing to do with ketoacidosis, which is a serious complication of uncontrolled diabetes.) Testing for ketones can be done quite simply by using urine test strips.
Of the numerous variations of the low or controlled carbohydrate diets around today, some are ketogenic and some not. Of the ketogenic type, the Atkins Diet is probably the best known and most widely used. SugarBusters, the Carbohydrate Addict's Diet, Protein Power, The Paleolithic Diet, Neanderthin, the Zone, the Go-Diet, Life Without Bread, the Eskimo Diet, the Stone Age Diet, the Schwarzbein Principle, the Specific Carbohydrate Diet, the South Beach Diet and Fat Flush Plan are some of the many other examples of low or controlled carb diets.
A very strict version of ketogenic diet has been used for many years in childhood epilepsy that failed to respond to anti-epileptic drugs. Although the mechanisms are not fully understood, the ketogenesis alters the metabolism of the brain in a way that can reduce the risk of seizures. However, this treatment for epilepsy fell out of favour over the years due to difficulty in keeping to the diet and concerns about cholesterol levels.
The concerns about cholesterol levels have now been shown to be groundless, and moreover, some epilepsy specialists, Dr Eric Kossoff in particular, have reported that less strict versions of the ketogenic diet, such as the Atkins Diet or a modified version of it, can be just as effective. Furthermore, the explosion in popularity of the Atkins and other low carb, ketogenic diets for weight loss purposes has enormously improved the availability of low carbohydrate food substitutes, cookbooks and restaurant menus, which should make it much easier for parents to cope with feeding a child on a ketogenic epilepsy diet. See some of the latest ketogenic epilepsy diet clinical studies.
The recipes in the Low Carb / Low GI Cookbook are particularly suitable for those following the Atkins Diet or a modified form of the Atkins Diet for seizures as they are extremely low in carbohydrates and fit well into the allowance of 10 to 20 grams of carbohydrate per day that are recommended for epileptics using the diet. Good results have also been obtained by starting the diet with a low level of carbs which is then increased after a period of time. The interactive features of the Low Carb / Low GI Cookbook are particularly useful as the carbohydrate values of individual ingredients are shown, and ingredients can be adjusted and carb counts automatically recalculated, according to the changing needs of the person using the diet. Recipes can also be added, and imported from other sources.
Low carb/GI vs low calorie diets
About the single worst thing you can do for long term weight loss is to restrict calories excessively. While very low calorie diets do take off weight quickly (which is what most people want), the long term results can be disastrous. The reason is that a severe reduction in calories (say to below 1200 a day) makes the body go into starvation mode, slowing metabolic rate. Once calories get below a certain point, even serious exercise will not prevent this slowing. And once you start eating again (as you can't starve yourself for ever), the lowered metabolic rate will cause you to gain weight even more easily than before. Additionally, significant calorie reduction triggers changes in fat storing enzymes, making them more active. Low carb and low GI (glycemic index) diets maintain calories at a high enough level to avoid this happening. This is explained more fully in "Why Can't I Lose Weight - The real reasons diets fail and what to do about it".
For many people, the effect of carbohydrates on their blood sugar levels is very much like an addictive drug, causing cravings which make dieting or even just controlling their eating effectively doomed from the start. Calorie-restricted diets do not address this problem, and may even aggravate it, if they emphasise intake of carbohydrates. Carbohydrate cravings usually disappear completely once past the initial few days of a low carb diet.
There are also significant differences in the type of weight lost on different types of diets. When you starve your body of calories, protein, and fat (as on the standard low fat/low calorie diet), it burns large amounts of both fat and muscle to provide energy. The loss of muscle reduces your basic metabolic rate, so you need to cut calories even more. On a low carb diet, your body burns mostly fat and very little lean muscle tissue, thereby preserving your metabolic rate. More detail on the importance of maintaining metabolic rate can be found in "Why Can't I Lose Weight".
Low carb diets are not crash or fad diets. They are based on the scientifically proven fact that some people (possibly the majority of the population) are metabolically unable to handle large amounts of carbohydrate. The best low carb diets allow the dieter, once the excess weight has been lost, to find their individual level of tolerance for carbohydrates and to get used to the new way of eating. They also gradually guide the dieter to the realisation that going back to the old way of eating will not only put the weight back on but will also expose them to the other health risks that having this type of metabolism is increasingly being shown to involve.
Advances in knowledge since the early days of low carb diets have also shown that the carbohydrate restriction does not need to be as severe as was previously thought necessary to be effective. The new palatability and variety this has afforded low carb diets has made them enjoyable enough for long term use, ie for maintenance once the excess weight is lost. To illustrate the point, low carbers more often refer to their 'way of eating' than their 'diet'. This acceptability as a permanent way of eating is a significant advantage, as keeping the weight off in the long term is important and it is widely acknowledged that low calorie/low fat diets have failed dismally to deliver in this respect.
There is a tendency for those who 'do the diet without reading the books' to adopt a restricted, boring and monotonous way of eating. This is more reflective of a failure to understand how low carb diets work than a lack of variation inherent in them. It is also possible that low carbers who first encountered low carb diets in the bad old days of the seventies are unaware of the improvement on the variety front, both in terms of foods permitted and availability of low carb substitutes. Other factors that undoubtedly play their part are a widespread lack of knowledge of carbohydrate values, low carb substitutes and/or lack of time to learn how to cook the low carb way.
Low GI and low GL diets
How do low GI and low GL diets work
GI stands for glycemic index, which is a way of measuring the rise in blood glucose (or 'blood sugar') after eating specific foods. It only applies to carbohydrates. For instance, a 500-calorie steak will not affect blood sugar levels significantly but a 500-calorie baked potato will. (For a more detailed explanation, see below.) Low GI diets (and low GL diets, which are explained later) are based on the principle that eating too much of the kind of food that makes your blood sugar rise fast and high is an important cause of overweight. (This is also the science upon which low carb diets such as the Atkins Diet are based).
Which diets are low GI
Weight-loss diets based on the GI principle are not new. The Montignac method, which dates back to the 1980s, is probably the earliest popular low GI diet and represented a radical change from the low calorie/low fat diets which were in fashion at the time.
In the late 1990s, low carb diets took centre stage, led by the Atkins Diet. Low carb diets, like low GI diets, are based on the blood sugar control principle. The low carb movement re-stimulated interest the relationship between blood sugar, insulin and the explosion of obesity that we see today in the Western world. Meanwhile, the inventors of the glycemic index, David Jenkins and Thomas Wolever of the University of Toronto, had been continuing the work they started in the 1970s/80s. Having developed the index primarily as a tool to help diabetics manage their blood sugar levels, they had begun to see its potential as a weight loss tool. A new wave of low GI diets was a logical follow-on, particularly for those who saw the Atkins Diet as too restrictive. (The Atkins Diet in fact only restricts 'bad' carbohydrates - 'good' carbs are positively encouraged up to the limit of the individual's tolerance to them. This last point is extremely important but is generally overlooked).
There are many variations of the low GI diet around today, including The Glucose Revolution Life Plan, The Good Carb Diet Plan, Good Carbs Bad Carbs and Nutrisystem Nourish. Most well-known are probably the GI Diet by Rick Gallop and the South Beach Diet by Dr A Agatston.
What carbohydrates are allowed on low GI diets
Low GI (and to a great extent low carb) eating means a return to the type of carbohydrate foods that our great-grandparents ate - the 'good' carbs - plenty of whole grains such as barley and oats, dried peas and beans, root vegetables and whole fruits. Our great-grandparents didn't have the processed foods made from highly refined white flour, sugar and other processed grains that have become our staple foods today. They were also more physically active than we are, with few labour-saving devices in the home, no cars to take them everywhere instead of walking and no highly automated industrial and agricultural production methods. In consequence, our great-grandparents were able to keep their blood sugar levels in a steady state, much in the way that nature intended.
Why is low GI a healthy way to eat
However, the position is different for most of us today. Our diet has changed significantly since the time of our great-grandparents. We eat large quantities of refined flour and sugar every day - foods our blood sugar control mechanisms were not designed to handle. These foods make our blood sugar rise very high very quickly. It is the job of insulin to get our blood sugar levels back within the correct range, by organising the transport of this excess sugar out of our bloodstream and into storage. Unfortunately for us, if we do not use up the stored energy, we get fat. For many of us, the constant outpouring of insulin also leads to the eventual exhaustion of our insulin-secreting organ, the pancreas. If this happens, we become diabetic. Constantly high insulin/blood sugar levels can also have other serious consequences, such as heart disease and complications commonly suffered by diabetics such as blindness, kidney failure and amputations.
Who else besides low GI dieters uses the glycemic index
Diabetics are generally recommended to select foods that rank low to moderate on the glycemic index as a way to help them balance their blood glucose levels. Athletes are also familiar with the glycemic index and use it to select foods which optimise their energy reserves.
Low carb dieters focus more on the total amount of carbohydrate rather than the relative speed with which the carbohydrate-containing food is absorbed. They do nevertheless take the GI effect into account, for instance, when choosing between a selection of foods with a similar carb content.
Are low GI diets better than low carb?
As yet there are few clinical studies showing how effective low GI diets might be from a purely weight loss point of view, whereas there is plenty of evidence supporting low carb diets in this respect. In all probability the issue boils down to the individual's tolerance to carbs - if your tolerance is not very high, then you are unlikely to lose weight simply by eating low GI foods. If this is the case, you would need to ensure that the low GI foods you eat are also very low in total carbs. One way to do this is to follow a low GI diet which also takes into account the glycemic load (see below for more detail). At this point the difference between a low GI diet and a low carb diet becomes very small. If on the other hand you have a reasonably high tolerance to carbs, then you would probably do well on a low GI diet - or equally, a quality low carb plan such as the Atkins Diet which encourages intake of 'good' carbs up to your individual level of tolerance.
That said, there is no doubt that eating the low GI (and low carb) way means eating less refined carbohydrates such as sugar and white flour (the 'bad' carbs) and more vegetables, whole fruits, fibre, whole grains, pulses, nuts and seeds (the 'good' carbs). Few would argue that this can be anything but beneficial for most people's long term health.
Similarities between low GI and low carb diets
Although the 'rules' may look different, the foods eaten on a low GI diet are very similar to those eaten on a low or controlled carb diet such as the Atkins Diet. Both approaches involve the avoidance of carbohydrate-dense highly processed foods. Both approaches encourage lots of healthy salads and vegetables (although the Atkins Diet is often misquoted as not allowing vegetables and fruits). The scientific reasoning behind these seemingly different diets is not contradictory. They are all based on the principle that many people cannot eat significant quantities of carbohydrate foods, particularly refined ones, without risking constant overproduction of insulin and its consequences.
In fact, it is not unusual for people who have succeeded on a low carb diet such as Atkins to 'move' to a low GI plan once they have reached the less strict 'lifetime maintenance' phase of the diet. (Whether this is really a move to a different diet or whether they are two slightly different routes towards eating the same things at this stage is a point for debate).
Both low carb and low GI diets are primarily concerned with controlling the type of carbohydrate foods eaten. They do not usually require calorie counting, or if they do, this is of secondary importance. Because some foods (sticky buns, pastries and sugar candy for instance) are so high in carbs and so high on the GI scale, these foods are likely to be prohibited by both low carb and low GI diets (as opposed to being permitted in small portions as they might be on a low calorie diet.)
Although low carb dieters are primarily focused on the total carb content of a food, GI rankings do nevertheless have some relevance for them. Low carbers may refer to the GI ranking to help them choose between a selection of foods with a similar carb content. The Atkins Diet also introduces the concept of 'glycemic load' (see below for more detail). This involves multiplying the glycemic index of the food by the carbohydrate content of the amount to be consumed. This gives a more meaningful picture of what the overall effect will be of eating that particular portion of food. For instance, if you rely on the GI alone, you may be put off eating carrots because they are surprisingly high on the glycemic scale. Looking instead at the 'glycemic load', it is obvious that carrots are still a good choice in terms of the effect the quantity you are likely to eat will have on your blood sugar.
Both low GI and low carb diets represent a return to whole, nutritious foods and a turning away from heavily processed foods such as mass produced breads, cakes, biscuits, mixes and sauces, ready meals, snacks, 'fast foods', fizzy drinks etc. These foods usually contain artificial colourings, flavourings and preservatives - the chemicals that we commonly refer to as 'E numbers' - in quantity. Both low GI and low carb diets are founded on eating healthily (as opposed to 'eat whatever you like as long as it is low in calories or fat-free'). They are both based on the premise that we would be much healthier if we went back to eating natural, whole foods the way Nature intended.
Differences between low GI and low carb diets
Low GI dieters do not count carbs, but choose their carbohydrate foods and menus based solely on the GI ranking of the food or meal. In contrast, low carb dieters count carbohydrates and, although they may also make food or meal choices according to the GI of a particular food or meal, the total carb count is of more importance to them.
Low GI diets generally include starchy vegetables (potatoes, parsnips, carrots etc), fruits, pulses and wholegrains from the outset. Many low carb diets however prohibit these 'good' carbs in their initial phase. The good carbs are then gradually added back into the diet according to the individual's ability to tolerate them. (Unfortunately some people do not have a very high carb tolerance - which is why low GI diets may not be restrictive enough for such people to lose weight on them. By the same token, some of the low carb plans are not low enough in carbs for some people either. This is one reason why the four phases of the Atkins Diet work so well - the dieter starts at the lowest level and works gradually up to the highest level he or she can tolerate without putting on weight.)
Both low GI and low carb diets are concerned to a certain degree with fats. However, low GI diets tend to promote the avoidance of fat, saturated fat in particular, whilst low carb diets, and most notably, the Atkins Diet, do not. (What is not often recognised is that the Atkins and other low carb diets have always paid attention to fat - but they distinguish between 'good' and 'bad fats'. For instance, olive oil and fish oils and certain saturated fats are 'good' fats, while trans fats (hydrogenated oils) are 'bad' fats. Unfortunately, saturated fat got the blame for the wrongdoings of trans fats years ago, before it was recognised that there was more than just one type of saturated fat. This fact is now becoming more widely recognised.)
One important difference between low GI and low carb diets is that low GI diets are currently more widely accepted in the medical world. This is because low GI diets are more closely aligned to the healthy eating guidelines promoted by most Western governments than low carb diets. (Official healthy eating advice still follows the principles that around 60 per cent of daily calories should come from carbohydrates and that the only healthy diet is a low fat one. Some clinicians, Dr Atkins included, have been saying for the past thirty years that these two principles are wrong, and recent clinical studies have consistently been proving them right. But mainstream medical acceptance of these new ideas is slow, mainly because of the need for many years of evidence-based research to support changes in government health policy. So in the meantime, all 'new' diets are measured against the existing, and many would say, outdated guidelines. For this reason, GI diets are more likely to be seen as acceptable by doctors, nutritionists and dieticians, whilst low carb diets, despite plenty of compelling scientific evidence, are very often not.)
Following a low GI Diet
A low GI diet can approximately be achieved by following the typical 'healthy eating' diet promoted by government health departments but choosing carbohydrates which fall towards the lower end of the GI scale. In other words, substituting foods such as sugar, cakes, biscuits, white bread and rice, sweets, starchy vegetables, sugary drinks and fruit juice with sugar-free whole grains, whole fruits, pulses, nuts and seeds and non-starchy vegetables.
Another way to look at it is that everything allowed on a low carb diet is permitted on a low GI Diet* - because foods that are low in carbs cannot have much of a glycemic effect. So the low GI dieter can for instance use recipes developed originally with low carbers in mind. (However, it does not necessarily work the other way round - many GI diet recipes are fine for low carbers, but some of them may contain a higher level of carbs than the individual can tolerate, if he/she is very carb-sensitive.)
* Some GI diets are more restrictive of fats than low carb diets generally are. Certain GI diets reflect a high fat content in a food by placing the food in the high GI column, or giving it a red rather than a green traffic light. This does not mean the food is actually high GI - it just means that that particular food is discouraged on that particular diet for other reasons.
What is the glycemic index
The glycemic index is a measurement of how much blood glucose increases after eating a specific food. It only applies to carbohydrate foods. Carbohydrates often used to be categorised as either simple (eg fruit sugars and table sugars) or complex (breads, pasta, grains). This was on the basis that simple carbohydrates tended to be absorbed faster than complex carbohydrates. Such simple classification is now considered to be fairly meaningless and the glycemic index is an attempt to provide a more accurate method.
Glucose is the reference food for the glycemic index, with its value arbitrarily set at 100. All other foods have to be tested (in humans) before they can be given a ranking in the glycemic index. (Not all foods have been tested so far). Volunteers eat a portion of the food which has been calculated to supply 50 g of carbohydrates and their blood sugar response is measured. On another occasion, the same volunteers are given the equivalent amount of glucose. A comparison of the two outcomes, averaged over a number of volunteers, allows the glycemic index of the food to be determined. For instance, a food causing half of the blood sugar rise of glucose is given a GI of 50.
Unfortunately the glycemic index is not a perfect method of classification, either. Many factors can influence the effect on the blood sugar of particular foods (not least because foods with different indexes may be eaten simultaneously). Take kidney beans, for example. They have a low GI of 27 - they are notoriously hard to digest. But baked potatoes have a GI of 93 - higher than that of almost all other foods, including ice cream (61), sweet potatoes (54), and white bread (70). Chocolate/candy bars on the other hand tend to have a relatively low GI, presumably because their fat content slows their digestion. Factors affecting the GI of a food include:
- Biochemical structure of the carbohydrate - for example, amylopectin is more readily absorbed than amylose
- Intestinal absorption
- Food particle size - smaller particles are absorbed faster
- Cooking and preparation - both mechanical and thermal processing break the food into smaller particles thus facilitating absorption
- Content and timing of the previous meal
- Accompanying foods that include fat, fibre, or protein - fat and protein decrease the speed with which the stomach empties, thus decreasing the rate of carbohydrate absorption.
The glycemic index of a food can also vary with crop varieties, growing conditions, geographic location, genetic strain, ripeness, acidity and fibre, protein and fat content. For this reason, glycemic index values for non-branded foods in reference tables can only be approximate. (Incidentally these factors also affect the accuracy of carbohydrate values).
Not all foods have been tested yet, but the list of GI and GL rankings on the Mendosa.com site is one of the most comprehensive. Note that GI lists don't include carbohydrate foods which contain very small amounts of carbohydrate, as these are unmeasurable by the methods currently used. It is difficult to get test volunteers to eat enough of a very low carb food to achieve the 50 grams worth of carbs which is the standard test portion! Such foods are often simply listed by GI diet authors as 'free foods' (but diabetics and those counting carbs still need to take account of these in their daily allowance.) These foods include salad vegetables and other non-starchy vegetables such as cauliflower, broccoli, tomatoes, onions, green/French beans, cabbage, eggplant/aubergine, mushrooms, courgettes/zucchini. Other foods which may not be listed for similar reasons are avocados, raspberries, strawberries, pecans, milk, cream cheese, hard cheese, ricotta, plain yoghurt and artificial sweeteners.
What are glycemic load (GL) diets
Some feel that the glycemic index is not the right way to assess the insulin-related effects of food. This is because it measures blood sugar response per gram of carbohydrate contained in a food, not per gram of the food. This can leads to some misleading results. For example, a parsnip has a glycemic index of 98, almost as high as pure sugar. But this ranking fails to take into account the large amount of parsnips you would have to eat to produce such a blood sugar response.
This problem is resolved with the concept of glycemic load. The GL is calculated by multiplying the GI ranking of the food by the amount of carbohydrate in the portion to be consumed, then dividing by 100. In other words, it measures the glucose/insulin response per gram of food rather than per gram of carbohydrate in that food. On this basis, the glycemic load of a parsnip is 10, while glucose has a relative load of 100 - a more meaningful result.