Sep 09
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The Glycemic Index
What is the Glycemic Index?
The glycemic index or GI describes this difference by ranking carbohydrates according to their effect on our blood glucose levels. Choosing low GI carbs – the ones that produce only small fluctuations in our blood glucose and insulin levels – is the secret to long-term health reducing your risk of heart disease and diabetes and is the key to sustainable weight loss. Actually, not all carbohydrate foods are created equal, therefore, they behave quite differently in each person’s body.
What are the benefits of the Glycemic Index?
Eating a lot of high GI foods can be detrimental to your health because it pushes your body to extremes. This is especially true if you are overweight and sedentary. Switching to eating mainly low GI carbs that slowly trickle glucose into your blood stream keeps your energy levels balanced and means you will feel fuller for longer between meals.
* Low GI diets help people lose and control weight
* Low GI diets increase the body’s sensitivity to insulin
* Low GI carbs improve diabetes control
* Low GI carbs reduce the risk of heart disease
* Low GI carbs reduce blood cholesterol levels
* Low GI carbs can help you manage the symptoms of PCOS
* Low GI carbs reduce hunger and keep you fuller for longer
* Low GI carbs prolong physical endurance
* High GI carbs help re-fuel carbohydrate stores after exercise
How to switch to a low GI diet
The basic technique for eating the low GI way is simply a “this for that” approach – i.e., swapping high GI carbs for low GI carbs. You don’t need to count numbers or do any sort of mental arithmetic to make sure you are eating a healthy, low GI diet.
* Use breakfast cereals based on oats, barley and bran
* Use breads with wholegrains, stone-ground flour, sour dough
* Reduce the amount of potatoes you eat
* Enjoy all other types of fruit and vegetables
* Use Basmati or Doongara rice
* Enjoy pasta, noodles, quinoa
* Eat plenty of salad vegetables with a vinaigrette dressing
A book that is resourceful, helpful, and has good information is called “The New Glucose Revolution for Diabetes.”
News Release and Study
More effective weight loss and heart healthbenefits with low GI carbohydrates plus or minus protein
The first study to compare low GI and high protein diets head-to-head, systematically varying the glycemic load (GL) from high to low was published in Archives of Internal Medicine July 24. It is also the first study to prove that low GL diets reduce blood glucose and insulin levels over the entire day.
Conducted by Prof Jennie Brand-Miller, Joanna McMillan-Price and colleagues from the University of Sydney, the study was a randomised, controlled comparison of four diets of varying GL on weight loss and reducing cardiovascular disease risk in young overweight or obese adults. All four diets were healthy diets based on high fibre foods with less than 30% of energy as fat (less than 10% as saturated fat). Two of the diets were high protein diets and two were low GI diets.
There are four key messages:
* Moderate reductions in GL make losing weight easier, particularly for women.
* A high carb diet based around low GI foods was overall the most effective for heart health – good news for those who love their carbs.
* If you have high triglyceride levels, the optimal diet for you will combine both high protein and low GI foods. (This was the diet with the lowest GL).
* Low GI wholegrain foods (such as traditional porridge oats) provided heart health benefits over and above those of high GI wholegrains (such as wholewheat flakes).
How the Study was Carried Out
The trial led by Joanna McMillan-Price of the University of Sydney’s Human Nutrition Unit enrolled 129 overweight/obese, free-living, young adults (98 women and 31 men with a BMI greater than 25) who were willing to eat red meat. The participants were randomly assigned to one of four weight-loss diets.
DIETS 1 and 2 were high carb (55% energy) with high GI or low GI carbs respectively and average protein intake (15%).
DIETS 3 and 4 were high protein (25% energy) and carb reduced (45% energy), again with high and low GI carbs respectively.
Day-long profiles confirmed that mixed meals in the four diets produced differential blood glucose and insulin responses as predicted by their calculated GL, carb content and GI.
One day a week, the young adults collected their key carb foods, portions of red meat and specially prepared frozen meals. They were given eating plans to help them to lose weight (6000 kJ/1400 cal for women and 8000 kJ/1900 cal for men) and encouraged to ‘eat to appetite’. At the same time they met with a dietitian who provided encouragement and answered any questions.
During weeks 1, 4 and 8 they kept a 3-day food diary so that the researchers could estimate food intake and assess compliance with the eating plans. Their weight was recorded each week and changes in body composition (fat mass and lean mass) at the beginning and on completion of the program. Fasting blood samples were measured for glucose, insulin and other measures before beginning the diet and during weeks 6 and 12.
The Findings
All four diets resulted in weight reduction but there were significant differences in the proportion of young adults who lost at least 5% of initial body weight (that is a clinically significant amount) over the 12 weeks.
The low GI, high carb diet (DIET 2) produced the best outcome overall, reducing both fat mass and LDL (bad) cholesterol.
The volunteers who followed the low GI, high carb diet (DIET 2) or the high protein, high GI diet (DIET 3), were twice as likely to achieve the goal of at least 5% weight loss. Unfortunately, DIET 3 also produced an elevation of total cholesterol and in LDL (bad) cholesterol.
DIET 4 with the lowest GL of all gave the best outcomes only in those who had high triglyceride levels which is a feature of the metabolic syndrome. They lost more body fat and showed the best improvement in the good HDL cholesterol ratio.
The conventional diet (DIET 1) was associated with the highest level of postprandial (post-meal) glycemia as well as the slowest rate of weight loss.
The Conclusions
In concluding, the researchers say: ‘This study suggests that dietary glycemic load and not just overall energy intake, influences weight loss and postprandial glycemia. Moderate reductions in GL appear to increase the rate of body fat loss, particularly in women. Diets based on low GI wholegrain products (in lieu of wholegrains with a high GI) maximise cardiovascular risk reduction, particular if protein intake is high. Reassuringly, this advice can optimise clinical outcomes within current nutrition guidelines without the concerns that apply to low carbohydrate diets.’
‘GL may be more relevant to women than men,’ they say. ‘Women generally lose weight more slowly and display differences in postprandial glucose and fat oxidation which might influence rate of fat loss.’
Speaking to GI News, Joanna McMillan-Price makes the point that: ‘While high protein and low GI diets may seem to be diametrically opposed, they in fact will both reduce GL. That is they both reduce your blood glucose and insulin levels.’
‘This fits with what we know about the paleolithic diet and our hunter/gatherer ancestors,’ she says. ‘Although they ate large amounts of meat when it was available, they also ate large amounts of plant foods (leaves, berries, nuts) which would have been gathered every day by the women ensuring that their diet was naturally low GI and low GL.’
The Take-Home Message
So what’s the take home message? First of all, one diet doesn’t have to fit all: What’s important is that you set yourself attainable goals and your diet is one you enjoy and can live with over the longer term. If it involves a lot of sacrifice and discipline on your part (eg, no sugar or carbs of any sort), it’s bound to fail sooner or later. Our tips:
Step 1 : Focus on reducing saturated fat and eating the good fats instead.
Step 2 : Choose low GI smart carbs to maximise body fat loss as well as cardiovascular benefits.
Step 3 : Aim to eat at least five serves of vegetables and two serves of fruit every day (preferably of three or more colours) including leafy greens, beans and peas, salad vegetables, pears, apples, oranges etc.
And be active. Get those legs, not the fingers, to do the walking.
- Archives of Internal Medicine 2006;166:1466-1475 ‘Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomised controlled trial.’
- Online http://archinte.ama-assn.org/cgi/content/short/166/14/1466
Funding
The National Heart Foundation of Australia and Meat and Livestock Australia contributed funding but did not participate in the study design or the collection, analysis, interpretation, writing of the manuscript or the decision to submit the paper for publication.
Christina’s Final Thought
Personally, I don’t think there is any one diet that works for someone nor should they even be dieting. Everyone should eat and do things in moderation. Carbohydrates and starches are a killer because they don’t fill you up, you are still hungry afterward, it makes your blood glucose spike to the roof and feel drowsy/tired/weak, it’s not sustaining, and it’s not the healthiest option of food.
Eating protein, fat, and omega-3s (and of course fruits, vegetables, broth based soups, and foods that have a high H20 content) are things that fill you up, its a steady source of energy, blood glucose doesn’t spike, you stay healthy, and lose or stay the same weight. If you have fat available, you will burn it and it won’t be hoarded by the body. Hence, when a person skips meals, doesn’t eat properly, doesn’t eat because they think that’s the way to lose weight etc., the body hoards the food in the body because the body doesn’t know when it will get it’s next meal so it tucks it away for storage/hibernation.