The GI was originally developed as tool to help diabetics manage their blood sugar. Thats because some foods, which are high on the glycemic index, cause a rapid rise in blood suagar. Other foods, which are low on the glycemic index, lead to a slower rise in blood sugar. This can be valuable information to have handy for diabetics and those with blood sugar concerns. However, the idea that choosing lower GI foods helps you lose weight is NOT supported by the research - it is merely used as "hook" for diet books. The GI is a tool for helping regulate blood sugar, not increasing fat loss.

It's certainly conceivable that some of the foods that are low on the GI might help reduce appetite or that those foods are simply lower in calories, thereby lowering total calorie intake, but then it wouldnt be the low GI per se that contributed to fat loss, but the lower calories (which is ALWAYS the case, by the way - fat loss is about calories first and foremost).

In the latest research that has been released in the years since the 2003 publication of the first edition of my Burn The Fat ebook, there's little doubt left that the low GI diets do not contribute significantly to improving fat loss. When researchers match two groups at the same calorie level and feed one group a high GI diet and one group a lower GI diet, the weight loss will be virtually identical. Blood sugar response, insulin response, and even blood lipids may show differences, for better or worse, but you will NOT see a difference in body fat.

Since my Burn The Fat program was NOT designed for diabetic issues or clinical blood sugar control issues, (it's for healthy people who simply want to burn fat), that is why I did not include the GI in my food lists or prescribe carbohydrate choices based on GI.

As for glycemic load, (GL), that is slightly more useful because GI tells you about blood sugar response but it doesn't tell you about how many calories are in the food. The GL takes into account both the glycemic index as well as the calorie count. For this reason, some people switched from using GI to the GL. However, in all the new research, even the GL did not make any difference in fat loss, if calories were equal.

There's nothing inherently wrong with following a low GI or low GL diet, and for those with blood sugar issues, it may be important. But for fat loss, it's not as helpful as a food selection tool as some diet authorities and glycemic / glucose / GI diet book authors want you to believe.

If you're the scientifically-minded type, I've compiled the latest research so you can see the evidence for yourself.

No effect of a diet with a reduced glycaemic index on satiety, energy intake and body weight in overweight and obese women. Aston, LM, et al. International Journal of Obesity. January 2008. Vol 32. pp 160-165. Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, UK

OBJECTIVE: To investigate whether a diet with a reduced glycaemic index (GI) has effects on appetite, energy intake, body weight and composition in overweight and obese female subjects. Design: Randomized crossover intervention study including two consecutive 12-week periods. Lower or higher GI versions of key carbohydrate-rich foods (breads, breakfast cereals, rice and pasta/potatoes) were provided to subjects to be incorporated into habitual diets in ad libitum quantities. Foods intended as equivalents to each other were balanced in macronutrient composition, fibre content and energy density.

SUBJECTS: Nineteen overweight and obese women, weight-stable, with moderate hyperinsulinaemia (age: 34-65 years, body mass index: 25-47 kgm
2, fasting insulin: 49-156 pmol l
1). Measurements: Dietary intake, body weight and composition after each 12-week intervention. Subjectively rated appetite and short-term ad libitum energy intake at a snack and lunch meal following fixed lower and higher GI test breakfasts (GI 52 vs 64) in a laboratory setting.

RESULTS: Free-living diets differed in GI by 8.4 units (55.5 vs 63.9), with key foods providing 48% of carbohydrate intake during both periods. There were no differences in energy intake, body weight or body composition between treatments. On laboratory investigation days, there were no differences in subjective ratings of hunger or fullness, or in energy intake at the snack or lunch meal.

CONCLUSION: This study provides no evidence to support an effect of a reduced GI diet on satiety, energy intake or body weight in overweight/obese women. Claims that the GI of the diet per se may have specific effects on body weight may therefore be misleading.

Glycaemic index effects on fuel partitioning in humans. Obes Rev. 2006 May;7(2):219-26.Diaz EO, et al. Laboratory of Energy Metabolism and Stable Isotopes, Institute of Nutrition and Food Technology (INTA), University of Chile, Ave. El Libano 5524, Macul, Santiago, Chile.

The purpose of this review was to examine the role of glycaemic index in fuel partitioning and body composition with emphasis on fat oxidation/storage in humans. This relationship is based on the hypothesis postulating that a higher serum glucose and insulin response induced by high-glycaemic carbohydrates promotes lower fat oxidation and higher fat storage in comparison with low-glycaemic carbohydrates. Thus, high-glycaemic index meals could contribute to the maintenance of excess weight in obese individuals and/or predispose obesity-prone subjects to weight gain. Several studies comparing the effects of meals with contrasting glycaemic carbohydrates for hours, days or weeks have failed to demonstrate any differential effect on fuel partitioning when either substrate oxidation or body composition measurements were performed. Apparently, the glycaemic index-induced serum insulin differences are not sufficient in magnitude and/or duration to modify fuel oxidation.

No difference in body weight decrease between a low-glycemic-index and a high-glycemic-index diet but reduced LDL cholesterol after 10-wk ad libitum intake of the low-glycemic-index diet. Sloth B, et al. Department of Human Nutrition, Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, 30 Rolighedsvej, DK-1958 Frederiksberg C, Denmark.

BACKGROUND: The role of glycemic index (GI) in appetite and body-weight regulation is still not clear.

OBJECTIVE: The objective of the study was to investigate the long-term effects of a low-fat, high-carbohydrate diet with either low glycemic index (LGI) or high glycemic index (HGI) on ad libitum energy intake, body weight, and composition, as well as on risk factors for type 2 diabetes and ischemic heart disease in overweight healthy subjects.

DESIGN: The study was a 10-wk parallel, randomized, intervention trial with 2 matched groups. The LGI or HGI test foods, given as replacements for the subjects' usual carbohydrate-rich foods, were equal in total energy, energy density, dietary fiber, and macronutrient composition. Subjects were 45 (LGI diet: n = 23; HGI diet: n = 22) healthy overweight [body mass index (in kg/m(2)): 27.6 +/- 0.2] women aged 20-40 y.

RESULTS: Energy intake, mean (+/- SEM) body weight (LGI diet: -1.9 +/- 0.5 kg; HGI diet: -1.3 +/- 0.3 kg), and fat mass (LGI diet: -1.0 +/- 0.4 kg; HGI diet: -0.4 +/- 0.3 kg) decreased over time, but the differences between groups were not significant. No significant differences were observed between groups in fasting serum insulin, homeostasis model assessment for relative insulin resistance, homeostasis model assessment for beta cell function, triacylglycerol, nonesterified fatty acids, or HDL cholesterol. However, a 10% decrease in LDL cholesterol (P < 0.05) and a tendency to a larger decrease in total cholesterol (P = 0.06) were observed with consumption of the LGI diet as compared with the HGI diet.

CONCLUSIONS: This study does not support the contention that low-fat LGI diets are more beneficial than HGI diets with regard to appetite or body-weight regulation as evaluated over 10 wk. However, it confirms previous findings of a beneficial effect of LGI diets on risk factors for ischemic heart disease.

Should obese patients be counselled to follow a low-glycaemic index diet? No. Raben A. Obes Rev. 2002 Nov;3(4):245-56. Research Department of Human Nutrition, Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Frederiksberg, Denmark.

In diabetes research the glycaemic index (GI) of carbohydrates has long been recognized and a low GI is recommended. The same is now often the case in lipid research. Recently, a new debate has arisen around whether a low-GI diet should also be advocated for appetite- and long-term body weight control. A systematic review was performed of published human intervention studies comparing the effects of high- and low-GI foods or diets on appetite, food intake, energy expenditure and body weight. In a total of 31 short-term studies (< 1 d), low-GI foods were associated with greater satiety or reduced hunger in 15 studies, whereas reduced satiety or no differences were seen in 16 other studies. Low-GI foods reduced ad libitum food intake in seven studies, but not in eight other studies. In 20 longer-term studies (< 6 months), a weight loss on a low-GI diet was seen in four and on a high-GI diet in two, with no difference recorded in 14. The average weight loss was 1.5 kg on a low-GI diet and 1.6 kg on a high-GI diet. To conclude, there is no evidence at present that low-GI foods are superior to high-GI foods in regard to long-term body weight control. However, the ideal long-term study where ad libitum intake and fluctuations in body weight are permitted

Reduced glycemic index and glycemic load diets do not increase the effects of energy restriction on weight loss and insulin sensitivity in obese men and women. J Nutr. 2005 Oct;135(10):2387-91. Raatz SK, et al. General Clinical Research Center, Department of Medicine, School of Public Health, University of Minnesota, Minneapolis, MN, USA

Reducing the dietary glycemic load and the glycemic index was proposed as a novel approach to weight reduction. A parallel-design, randomized 12-wk controlled feeding trial with a 24-wk follow-up phase was conducted to test the hypothesis that a hypocaloric diet designed to reduce the glycemic load and the glycemic index would result in greater sustained weight loss than other hypocaloric diets. Obese subjects (n = 29) were randomly assigned to 1 of 3 diets providing 3138 kJ less than estimated energy needs: high glycemic index (HGI), low glycemic index (LGI), or high fat (HF). For the first 12 wk, all food was provided to subjects (feeding phase). Subjects (n = 22) were instructed to follow the assigned diet for 24 additional weeks (free-living phase). Total body weight was obtained and body composition was assessed by skinfold measurements. Insulin sensitivity was assessed by the homeostasis model (HOMA). At 12 wk, weight changes from baseline were significant in all groups but not different among groups (-9.3 +/- 1.3 kg for the HGI diet, -9.9 +/- 1.4 kg for the LGI diet, and -8.4 +/- 1.5 kg for the HF diet). All groups improved in insulin sensitivity at the end of the feeding phase of the study. During the free-living phase, all groups maintained their initial weight loss and their improved insulin sensitivity. Weight loss and improved insulin sensitivity scores were independent of diet composition. In summary, lowering the glycemic load and glycemic index of weight reduction diets does not provide any added benefit to energy restriction in promoting weight loss in obese subjects.

Tom Venuto is a lifetime natural (steroid-free) bodybuilder, independent nutrition researcher, freelance writer and author of the #1 best selling diet e-book, Burn The Fat, Feed The Muscle and the #1 Amazon best-seller, The Body Fat Solution (Avery/Penguin books). Tom has written hundreds of articles and has been featured in IRONMAN, Australian IRONMAN, Natural Bodybuilding, Muscular Development, Exercise for Men, Men's Fitness, Men’s Exercise as well as on hundreds of websites worldwide. Tom is also the founder and CEO of the Internet's premier fat loss support community, the: Burn The Fat Inner Circle. To get notified of updates to TomVenuto.Com, subscribe to the free newsletter at: www.TomVenuto.com/free_newsletter.