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How effective is the consumption of low glycemic index foods?



Reducing Energy Intake and Promoting Weight Loss Conclusion Statement

Eight randomized controlled trials report no significant differences in energy intake or body weight after the consumption of a low-glycemic index diet.

Reducing Fat Mass Conclusion Statement

The effect on body fat mass is less conclusive than the research on the effects of consumption of low glycemic foods on energy intake and weight loss. Further research is needed to determine the effect of a low-glycemic index diet on body fat mass.

Evidence Summary

Randomized Controlled Trials

Eight randomized controlled trials (five + quality and three Ø quality) show no significant differences in energy intake or body weight after the consumption of a low-glycemic index diet. Three studies (all + quality) report no differences in fat mass, while one Ø quality study reported improvements in body fat mass.

In the + quality randomized controlled trial by Thompson et al, 2005, 90 obese men and women were randomized to three 500 kcal per day deficit diets defined as standard (average level of calcium and fiber and two dairy servings), high dairy (average level of fiber and four dairy servings) or high fiber/high dairy/low glycemic index (increased fiber through additional whole grains, fruits and vegetables, four dairy servings and foods with glycemic index > 100 were discouraged). After 48 weeks, 72 subjects completed the study (20% dropout rate). Significant weight loss occurred with all three diets, but the difference between diets was insignificant (standard diet: 10.0±6.8 kg; high dairy diet: 11.8±6.1 kg; high fiber/high dairy/low glycemic index diet: 10.6±7.9 kg, P=0.45). There was no significant difference among the three groups in calories prescribed, caloric intake, exercise minutes, body fat loss, trunk fat loss or change in waist or hip circumference.

In a + quality randomized controlled trial by Frost et al, 2004, 55 adults with coronary heart disease followed a healthy eating diet plan either with or without an emphasis on low glycemic index carbohydrates for 12 weeks. There were no significant differences between groups with regard to weight, waist circumference or biochemical measures.

In a + quality randomized controlled trial by Alfenas and Mattes, 2005, on 39 healthy normal-weight subjects consuming only low- or high-glycemic index foods, ad libitum, in a laboratory for two experimental eight-day sessions, there were no significant differences between treatments in appetite or energy intake.

In a + quality randomized controlled trial by Sloth et al, 2004, on 45 overweight women following either a low-glycemic index diet or a high-glycemic index diet for 10 weeks, there were no differences between groups in energy intake, body weight and fat mass changes.

In a + quality randomized controlled trial by Pereira et al, 2004, on 46 overweight or obese young adults following low-fat vs. low-glycemic load diets at 60% of energy needs to lose 10% of body weight, 39 completed the trial. The rate of weight loss between diets was not significant (1.09±0.05 vs. 0.99±0.05 kg per week for low-glycemic load and low-fat diets, respectively, P=0.19). The decline in REE was lower by 80 kcal per day and there was less hunger on the low-glycemic load diet vs. the low-fat diet (P=0.04).

In a Ø quality randomized controlled trial by Carels et al, 2005, of 53 obese subjects on a behavioral weight loss program with or without glycemic index education for 20 weeks, 40 completed the study (75.5%). At post-treatment, participants in the glycemic index education group had significantly greater glycemic index knowledge (P<0.05) and consumed foods with a lower average daily glycemic index (P<0.05), but glycemic index education had no significant impact on body weight, BMI or body fat at post-treatment or one-year follow-up.

In a Ø quality randomized controlled crossover trial by Bouche et al, 2002, on 11 moderately overweight nondiabetic men, allocated to five weeks of a low-glycemic-index (41.0±1.0%) diet or a high-glycemic-index (71.3±1.3%) diet separated by a five-week washout interval, there were no differences during the diet periods with regard to total daily energy intake or body weight. Despite the lack of change in body weight, the low-glycemic-index diet period was associated with a decrease in total fat mass by ~700 g (P<0.05) and a tendency to increase lean body mass (P<0.07). Although all subjects were asked to maintain their usual lifestyle during the experimental period, physical activity was not measured nor controlled for as a confounding variable.

In a Ø quality randomized controlled trial by Ebbeling et al, 2005, on 34 obese young adults following an ad libitum low-glycemic load diet or conventional energy-restricted (250-500 kcal per day deficit) low-fat diet for 12 months, only 23 completed the study (dropout rate of 32.4%). Despite the low-glycemic load diet being an ad libitum diet, while the conventional diet was energy restricted, energy intake did not differ between the groups. Body weight decreased significantly in both groups after six months (-8.4% for low-glycemic load diet and -7.8% for conventional diet) and 12 months (-7.8% and -6.1%, respectively), but mean weight loss did not differ between the groups.

Cohort Study

In a Ø quality cohort study of the Ontario Cardiac Rehabilitation Pilot Project by LaHaye et al, 2005, 120 subjects following a low-glycemic load diet at one site were compared with the 1,434 subjects in 16 other sites across Ontario, following an isocaloric diet based on Canada’s Food Guide to Healthy Eating for People Four Years and Over. Subjects on the low-glycemic load diet lost more weight at six months (2.8 kg loss vs. 0.2 kg gain, P<0.0001) and had a greater reduction in abdominal obesity (2.9 cm vs. 0.4 cm, P<0.0001).

Overview Table

Article (worksheet) Study Design Quality Rating of Article Sample Size Sex of Population Studied Race Intervention / Association Description Prescribed Caloric Intake Actual caloric intake Diet Outcomes Behavioral Outcomes Adiposity Outcomes
Alfenas RC, Mattes RD 2005 Class A Plus 39 Males, Females Not Specified Healthy normal-weight subjects consuming only low- or high-glycemic index foods, ad libitum, in a laboratory for two experimental eight-day sessions NA Not reported Group glycemic responses (low- versus high-glycemic index foods) and insulinemic responses did not significantly differ following breakfast or lunch on day 1 or 8 of either session. No significant differences between treatments in appetite or energy intake. There were no significant group differences in hunger, fullness, or desire to eat ratings.  
Frost GS, Brynes AE et al 2004 Class A Plus 55 Males, Females Not Specified Adults with coronary heart disease followed a healthy eating diet plan either with or without an emphasis on low glycemic index carbohydrates for 12 weeks Not reported Reported by group Aim of the study was to induce a 20% drop in glycemic index, but a decrease of only 13% was achieved.   There were no significant differences between groups with regard to weight, waist circumference or biochemical measures.
Pereira MA, Swain J et al 2004 Class A Plus 39 Males, Females African American, Hispanic, Caucasian, Other Overweight or obese young adults following low-fat vs. low-glycemic load diets at 60% of energy needs to lose 10% of body weight 60% of energy needs, 1500 kcal Not reported   Participants receiving the low-glycemic load diet reported less hunger than those receiving the low-fat diet (P = 0.04). Individual rates of weight loss were nonsignificantly greater in the low-glycemic load group (1.09 +/- 0.05 vs 0.99 +/- 0.05 kg/week, P = 0.19). REE decreased less with the low-glycemic load diet than with the low-fat diet.
Sloth B, Krog-Mikkelsen I et al 2004 Class A Plus 45 Females Not Specified Overweight women following either a low-glycemic index diet or a high-glycemic index diet for 10 weeks NA Reported by group No significant differences between low-GI and control groups in terms of energy intake.   No significant differences between low-GI and control groups in terms of weight change or fat mass.
Thompson W, Rostad Holdman N et al 2005 Class A Plus 72 Males, Females Not Specified Obese men and women were randomized to three 500 kcal per day deficit diets defined as standard (average level of calcium and fiber and two dairy servings), high dairy (average level of fiber and four dairy servings) or high fiber/high dairy/low glycemic index (increased fiber through additional whole grains, fruits and vegetables, four dairy servings and foods with glycemic index > 100 were discouraged). 500 kcal per day deficit There was no significant difference among the three groups in caloric intake     Significant weight loss occurred with all three diets, but the difference between diets was insignificant (standard diet: 10.0±6.8 kg; high dairy diet: 11.8±6.1 kg; high fiber/high dairy/low glycemic index diet: 10.6±7.9 kg, P=0.45).
Bouche C, Rizkalla SW et al 2002 Class A Neutral 11 Males Not Specified Moderately overweight nondiabetic men, allocated to five weeks of a low-glycemic-index (41.0±1.0%) diet or a high-glycemic-index (71.3±1.3%) diet separated by a five-week washout interval Not reported Not reported No differences during the diet periods with regard to total daily energy intake   Despite the lack of change in body weight, the low-glycemic-index diet period was associated with a decrease in total fat mass by ~700 g (P<0.05) and a tendency to increase lean body mass (P<0.07).
Carels RA, Darby LA et al 2005 Class A Neutral 40 Males, Females Not Specified Obese subjects on a behavioral weight loss program with or without glycemic index education for 20 weeks Not reported (Post-treatment measurements) Regular weight loss group: 1659 +/- 433; Low-glycemic education group: 1674 +/- 586 At post-treatment, participants in the glycemic index education group consumed foods with a lower average daily glycemic index (P<0.05). There was a significant decrease in total calories (p < 0.01). Participants not receiving GI education attended significantly more sessions (15.6) compared to those receiving the education (13.1) [F(1, 40) = 6.79, p < 0.01]. Glycemic index education had no significant impact on body weight, BMI or body fat at posttreatment or 1 year follow-up.
Ebbeling CB, Leidig MM et al 2005 Class A Neutral 23 Males, Females Not Specified Obese young adults following an ad libitum low-glycemic load diet or conventional energy-restricted (250-500 kcal per day deficit) low-fat diet for 12 months conventional diet: 250-500 kcal per day deficit; low-glycemic diet: ad libitum   Despite the low-glycemic load diet being an ad libitum diet, while the conventional diet was energy restricted, energy intake did not differ between the groups.   Body weight decreased significantly in both groups after six months (-8.4% for low-glycemic load diet and -7.8% for conventional diet) and 12 months (-7.8% and -6.1%, respectively), but mean weight loss did not differ between the groups.
LaHaye SA, Hollett PM et al 2005 Class B Neutral 120 Males, Females Not Specified 120 subjects following a low-glycemic load diet at one site were compared with the 1, 434 subjects in 16 other sites across Ontario, following an isocaloric diet based on Canada’s Food Guide to Healthy Eating for People Four Years and Over. Canada Food Guide diet: 1800 kcal/day, 55% of kcals from carbohydrate, daily glycemic load of 140; Low glycemic load diet: 1800 kcal/day, 45% from carbohydrate to achieve daily glycemic load of 85 Not reported     Subjects on the low-glycemic load diet lost more weight at six months (2.8 kg loss vs. 0.2 kg gain, P<0.0001) and had a greater reduction in abdominal obesity (2.9 cm vs. 0.4 cm, P<0.0001).




Quality Rating Summary
For a summary of the Quality Rating results, click here.
Worksheets
Alfenas RCG, Mattes RD.  Influence of glycemic index/load on glycemic response, appetite, and food intake in healthy humans.  Diabetes Care 2005; 28: 2123 - 2129.

Bouche C, Rizkalla SW, Luo J, Vidal H, Veronese A, Pacher N, Fouquet C, Lang V, Slama G.  Five-week, low-glycemic index diet decreases total fat mass and improves plasma lipid profile in moderately overweight nondiabetic men.  Diabetes Care 2002; 25: 822-828.

Carels RA, Darby LA, Douglass OM, Cacciapaglia HM, Rydin S.  Education on the glycemic index of foods fails to improve treatment outcomes in a behavioral weight loss program.  Eating Behaviors 2005; 6(2): 145-150.

Ebbeling CB, Leidig MM, Sinclair KB, Seger-Shippee LG, Feldman HA, Ludwig DS.  Effects of an ad libitum low-glycemic load diet on cardiovascular disease risk factors in obese young adults.  Am J Clin Nutr 2005; 81: 976-982.

Frost GS, Brynes AE, Bovill-Taylor C, Dornhorst A.  A prospective randomised trial to determine the efficacy of a low glycaemic index diet given in addition to healthy eating and weight loss advice in patients with coronary heart disease.  Eur J Clin Nutr 2004; 58: 121-127.

LaHaye SA, Hollett PM, Vyselaar JR, Shalchi M, Lahey KA, Day AG.  Comparison between a low glycemic load diet and a Canada Food Guide diet in cardiac rehabilitation patients in Ontario.  Can J Cardiol 2005; 21(6): 489-494.

Pereira MA, Swain J, Goldfine AB, Rifai N, Ludwig DS.  Effects of a low-glycemic load diet on resting energy expenditure and heart disease risk factors during weight loss.  JAMA 2004; 292: 2,482 - 2,490.

Sloth B, Krog-Mikkelsen I, Flint A, Tetens I, Bjorck I, Vinoy S, Elmstahl H, Astrup A, Lang V, Raben A. No difference in body weight decrease between a low-glycemic-index and a high-glycemic-index diet but reduced LDL cholesterol after 10-week ad libitum intake of the low-glycemic-index diet. Am J Clin Nutr. 2004; 80: 337-347.

Thompson WG, Rostad Holdman N, Janzow DJ, Slezak JM, Morris KL, Zemel MB.  Effect of energy-reduced diets high in dairy products and fiber on weight loss in obese adults.  Obesity Research 2005; 13(8): 1344-1353.

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