The Glycemic Index (GI) is a measure of the rate carbohydrate in foods is broken down into glucose (sugar) and released into the blood stream, where it can be used for energy. Foods with a low GI value (55 or less) are ideal, as low GI foods provide sustained energy release and help keep blood glucose levels on an even keel. This has flow on effects including improved performance, appetite reduction, weight management/loss and diabetes and heart disease risk reduction. Carbohydrate is an essential part of our diets – but not all carbohydrate foods are equal and the GI is the best way to help people chose the carbohydrate food that suits their needs.
There are three ratings for GI:
- Low = GI value 55 or less
- Medium = GI value 56 – 69 inclusive
- High = GI 70 or more
Why everyone can benefit from following a low GI diet?
10 top reasons for going Low GI.
1. Lose more weight and body fat and keep it off by feeling fuller for longer and reducing cravings
Foods with a low GI value slowly release glucose (a kind of sugar) into the blood slowly, providing you with a steady supply of energy, leaving you feeling fuller for longer and helping to reduce the drive to eat so that you're less likely to snack and therefore more likely to reduce your total kilojoule intake.
Studies1,2 have also shown there to be benefits in reducing abdominal fat, due to the role low GI foods play in increasing insulin sensitivity. This allows you to burn more fat as a fuel source and process your carbohydrates more efficiently.
It has also been proven that by eating a healthy low GI, higher protein diet after losing weight, you are more likely to maintain the weight than other weight maintenance diets3.
The low GI symbol foods are all round healthy choices in their food category, so they are lower fat, lower salt and of course, low GI.
2. Maintain energy levels by preventing blood glucose (sugar) fluctuations4
Low GI foods are broken down slowly and keep blood glucose levels stable and therefore maintain energy levels. The sustaining power of a low GI diet allows you to trickle glucose into your system over a longer period of time, and have a more stable energy level, rather than peaks and troughs of energy throughout the day. Including mostly low GI foods in each meal and when snacking assists busy people to keep themselves free of the burden of poor concentration, and energy lows.
3. Decrease the risk of type 2 diabetes, and improves the management of diabetes 5-8
A healthy low GI Diet has long been used for improving people with diabetes blood glucose management. People with Type 1 diabetes can also use the GI to manage their glucose levels and insulin regimes.
Following a low-GI diet can also reduce the risk of developing type 2 diabetes; a lifestyle disease which affects over a million people in Australia. People with Type 2 diabetes can follow a healthy low GI diet to keep their weight under control and help manage their blood glucose levels.
Low GI diets have been shown to improve both blood cholesterol and glucose levels, and reduce insulin resistance, which is important in reducing the risk of long term diabetes-related complications
4. Improve cholesterol levels by lowering LDL and raising HDL 9-11
A low GI diet will increase the good blood fats – HDL’s and reduce the bad fats - LDL’s. Cholesterol levels can be improved by having more ‘good’ cholesterol and less ‘bad’ cholesterol in your blood.
5. Decrease the risk of cardiovascular disease by reducing inflammation 12-14
More and more evidence for the benefit of a healthy low GI diet in improving heart health is coming out each year, by:
· Reducing post-meal blood glucose levels which improve the elasticity of the artery walls, making vessel expansion easier and improving blood flow.
· Improving blood cholesterol levels
· Promoting abdominal fat loss
6. Improve cognitive performance – fuel for the brain 15-18
Low GI foods provide a steady supply of fuel (glucose) to the brain improving cognitive performance.
For children and teens, eating a low GI breakfast has been associated with improved learning and better school performance. It provides a more constant level of blood glucose compared with the fluctuating glycemic response to a high GI breakfast, resulting in a smaller decline in concentration.
Eating a wide variety of low GI foods at various times throughout the day will maximize mental performance and decrease damaging spikes and drops in blood glucose levels throughout the day.
7. Reduce acne by reducing insulin levels 19-22
High insulin levels which result from eating high GI foods are associated with acne. A healthy low GI diet can reduce acne by more than 50% in 12 weeks. The recommended dietary changes are simple and include eating more lean protein and low GI foods and avoiding takeaway and highly processed foods.
8. Decrease the risk of some cancers by reducing insulin levels23-24
Consuming a healthy low GI diet reduces both blood glucose and insulin levels, helping us to burn more fat and avoid weight gain over the longer term. Insulin is a hormone that drives cell growth and multiplication. High GI diets are associated with an increased risk of certain cancers that are sensitive to insulin including some breast cancers and bowel cancer.
9. Improve athletic performance through sustained energy release25-29
Eating a healthy low GI diet is one of the best ways all Australians can maximise their performance in their chosen sport to achieve their personal best. Low GI carbohydrates are slowly digested and absorbed and help sustain performance levels.
Low GI foods have been proven to extend endurance when eaten 1 - 2 hours before prolonged strenuous exercise.
10. Improved pregnancy outcomes through weight and insulin management30-33
1 in every 6 pregnant Australian women will be diagnosed with gestational diabetes in 2012. A healthy low GI diet will reduce the risk of women developing this condition.
Diabetes in pregnancy is a major health problem. There is a very strong link between higher blood glucose levels and the rate of caesarean section, the rate of shoulder dystocia (where the baby’s shoulder is too large for the birth canal) and the chance of having a very large baby.
Gestational diabetes is also linked to the epidemic of child obesity. 1 in 5 children are now classified as overweight or obese at the young age of only 2 -3 years. It has been proven that birth weight is linked to the mother’s blood glucose levels during pregnancy.
The best way to reduce birth weight and the risk of an overweight child is to help pregnant women reduce their blood glucose levels – eating a healthy low GI diet is key.
References:
Weight Management:
1. Thomas et al. Low glycaemic index or low glycaemic load diets for overweight and obesity, The Cochrane Library 2007, Issue 3
2. Pawlak et al. Long-term effects of dietary glycemic index on adiposity, energy metabolism, and physical activity in mice. Lancet. 2004; 364(9436): 778-85
3. Larsen et al. Diets with high or low protein content and glycemic index for weight-loss maintenance. N Engl J Med. 2010 25;363(22):2102-13.
Energy Levels
4. Brand-Miller et al. Glycemic index, postprandial glycemia, and the shape of the curve in healthy subjects: analysis of a database of more than 1,000 foods, Am J Clin Nutr. 2009; 89: 97–105
Diabetes Management:
5. Goyenechea et al. Effects of different protein content and glycemic index of ad libitum diets on diabetes risk factors in overweight adults: the DIOGenes multicentre, randomised, dietary intervention trial, Diabetes Metab Res Rev. 2011 May 17.
6. Thomas et al. Low glycaemic index, or low glycaemic load, diets for diabetes mellitus. The Cochrane Library 2009, Issue 1
7. Barclay et al. Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. Am J Clin Nutr. 2008; 87:627-37
8. Anderson et al. Carbohydrate and fiber recommendations for individuals with diabetes: a quantitative assessment and meta-analysis of the evidence. American College of Nutrition. 2004; 23(1): 5-17.
Improve Cholesterol Levels:
9. Philippou et al. Preliminary report: the effect of a 6-month dietary glycemic index manipulation in addition to healthy eating advice and weight loss on arterial compliance and 24-hour ambulatory blood pressure in men: a pilot study. Metabolism. 2009; 58(12):1703-8.
10. Levitan et al. Dietary glycemic index, dietary glycemic load, blood lipids, and C-reactive protein. Metabolism Clinical and Experimental. 2008; 57: 437–443
11. Anderson et al. Carbohydrate and fiber recommendations for individuals with diabetes: a quantitative assessment and meta-analysis of the evidence. American College of Nutrition. 2004; 23(1): 5-17.
Cardiovascular Disease
12. Gögebakan et al. Effects of weight loss and long-term weight maintenance with diets varying in protein and glycemic index on cardiovascular risk factors: the diet, obesity, and genes (DiOGenes) study: a randomized, controlled trial. Circulation. 2011 Nov 21.
13. Mente et al. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Ann Intern Med. 2009; 169(7):659-669
14. Barclay et al. Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. Am J Clin Nutr. 2008; 87:627-37
Improve Cognitive Performance:
15. Micha et al. Glycaemic index and glycaemic load of breakfast predict cognitive function and mood in school children: a randomised controlled trial. Eur J Clin Nutr 2010; 64(9):948-57.
16. Ingwersen et al. A low glycaemic index breakfast cereal preferentially prevents children's cognitive performance from declining throughout the morning. Appetite 2007; 49(1):240-4.
17. Benton et al. The influence of the glycaemic load of breakfast on the behaviour of children in school. Physiol Behav 2007; 92(4):717-24.
18. Mahoney et al. Effect of breakfast composition on cognitive processes in elementary school children. Physiol Behav 2005; 85(5):635-45.
Reduce Acne
19. Spencer et al. Diet and acne: a review of the evidence. International Journal of Dermatology. 2009; 48: 339–347
20. Smith et al. The effect of a low glycemic load diet on acne vulgaris and the fatty acid composition of skin surface triglycerides. Journal of Dermatological Science 2008; 50: 41—52
21. Smith et al. A low-glycemic-load diet improves symptoms in acne vulgaris patients: a randomized controlled trial. Am J Clin Nutr 2007; 86: 107–115.
22. Smith, et al. The effect of a high-protein, low glycemic-load diet versus a conventional, high glycemic-load diet on biochemical parameters associated with acne vulgaris: a randomized, investigator-masked, controlled trial. J Am Acad Dermatol 2007; 57: 247–256.
Decrease the risk of some cancers
23. Dong and Qin. Dietary fiber intake and risk of breast cancer: a meta-analysis of prospective cohort studies. Breast Cancer Research and Treatment, 2011
24. Barclay et al. Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. Am J Clin Nutr. 2008; 87:627-37
Improve Athletic Performance
25. Moore et al. Effect of the glycaemic index of a pre-exercise meal on metabolism and cycling time trial performance. J Sci Med Sport. 2010 Jan;13(1):182-8
26. Cheng et al. Effect of dietary glycemic index on substrate transporter gene expression in human skeletal muscle after exercise. Eur J Clin Nutr. 2009; 63(12):1404-10
27. Mondazzi and Arcelli. Glycemic index in sport nutrition. J Am Coll Nutr. 2009 Aug;28 Suppl:455S-463S
28. Stevenson et al. Dietary glycemic index influences lipid oxidation but not muscle or liver glycogen oxidation during exercise. Am J Physiol Endocrinol Metab. 2009;296(5):E1140-7
29. Moore et al. The effects of low- and high-glycemic index meals on time trial performance. Int J Sports Physiol Perform. 2009 Sep;4(3):331-44
Improved Pregnancy Outcomes
30. Louie et al. Glycemic index and pregnancy: a systematic literature review. J Nutr Metab. 2010;2010:282464
31. McGowan and McAuliffe. The influence of maternal glycaemia and dietary glycaemic index on pregnancy outcome in healthy mothers. Br J Nutr. 2010;104(2):153-9
32. Moses et al. Can a low-glycemic index diet reduce the need for insulin in gestational diabetes mellitus? A randomized trial. Diabetes Care, 2009; 32(6): 996-1000
33. Moses et al. Effect of a low-glycemic-index diet during pregnancy on obstetric outcomes. Am J Clin Nutr 2006; 84:807–12