Low-glycemic diet trials comparison
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Trial numberStudyTitleSubjectsLengthInterventionDiet detailsDiet controlled for GI/GL?OutcomesNotes
1Ebbeling et al. 2007Effects of a Low–Glycemic Load vs Low-Fat Diet in Obese Young Adults73 young adults with obesity18 monthsLow-glycemic-load vs. low-fat diet, neither calorie restricted"Participants were counseled to consume low–glycemic load foods (particularly nonstarchy vegetables, legumes, and temperate fruits) and to limit intake of high–glycemic load foods (such as refined grains, starchy vegetables, fruit juices, and sweets). Attention also was directed toward consuming sources of healthful fat including nuts, seeds, and oils. The target macronutrient composition was 40% of energy from carbohydrate, emphasizing low–glycemic index sources, 35% from fat, and 25% from protein. Participants were equipped with food-choice lists that delineated products into low–, moderate–, and high–glycemic load categories.17 Registered dietitians provided information during cooking demonstrations to encourage consumption of low–glycemic load foods and led interactive activities using food models to define appropriate serving sizes of high–glycemic load foods (eg, refined grain products, sweets)." "Participants were counseled to consume low-fat grains, vegetables, fruits, and legumes and to limit intake of added fats, sweets, and high-fat snacks. The target macronutrient composition was 55% of energy from carbohydrate, 20% from fat, and 25% from protein. The intervention was not designed to maximize dietary glycemic index and glycemic load; rather, the aim was to prescribe a diet consistent with low-fat guidelines.18 Participants were equipped with food-choice lists that delineated products into low-, moderate-, and high-fat categories. Registered dietitians provided information during cooking demonstrations to encourage consumption of low-fat foods and led interactive activities using food models to define appropriate serving sizes of high-fat foods (eg, butter) and sweets."NoNo difference in weight or fat loss between groups. In subgroup analysis, glucose-stimumated insulin secretion predicted diet effectiveness.Carbohydrate intake was higher and fat intake was lower on the low-fat diet
2Jenkins et al. 2008Effect of a Low–Glycemic Index or a High–Cereal Fiber Diet on Type 2 Diabetes210 adults with type 2 diabetes6 monthsLow–glycemic-index vs. high-cereal-fiber dietary advice"In the low–glycemic index diet, the following foods were emphasized: low–glycemic index breads (including pumpernickel, rye pita, and quinoa and flaxseed) and breakfast cereals (including Red River Cereal [hot cereal made of bulgur and flax], large flake oatmeal, oat bran, and Bran Buds [ready-to-eat cereal made of wheat bran and psyllium fiber]), pasta, parboiled rice, beans, peas, lentils, and nuts (Table 1). In the high–cereal fiber diet, participants were advised to take the “brown” option (whole grain breads; whole grain breakfast cereals; brown rice; potatoes with skins; and whole wheat bread, crackers, and breakfast cereals) (Table 1). Six servings were prescribed for a 1500-kcal diet, 8 servings for a 2000-kcal diet, and 10 servings for a 2500-kcal diet. Detailed advice was also given to avoid starchy foods not directly recommended as part of the treatment, including those foods advised in the alternative treatment.In both diets, participants were specifically advised to avoid foods such as pancakes, muffins, donuts, white buns, bagels, rolls, cookies, cakes, popcorn, french fries, and chips. Three servings of fruit and 5 servings of vegetables were encouraged on both treatments. In the low–glycemic index diet, temperate fruit was the focus, including apples, pears, oranges, peaches, cherries, and berries; and in the high–cereal fiber diet, tropical fruit, such as bananas, mangos, guavas, grapes, raisins, watermelon, and cantaloupe, were emphasized. Participants were also advised against eating fruit recommended in the alternative treatment."ModeratelyLow-glycemic-index diet led to lower HbA1c and higher HDLFiber intake was higher on the low-GI diet
3Moses et al. 2009Can a Low–Glycemic Index Diet Reduce the Need for Insulin in Gestational Diabetes Mellitus?63 women with gestational diabetes12 monthsLow-glycemic-index vs. "conventional high-fiber" diet"The CHO intake was designed to achieve a minimum of 175 g/day with only the recommended choice of CHO foods varying. The dietary advice was individualized with specific mention of the energy and nutrient balance to achieve normal weight gain during the third trimester. The low–glycemic index diet was based on previously verified low–glycemic index food (11), including pasta, grain breads, and unprocessed breakfast cereals with a high fiber content. Women were specifically asked to avoid consuming white bread, processed commercial breakfast cereals, potatoes, and some rice varieties. Women in the conventional, higher–glycemic index diet group were advised to follow a diet with a high-fiber and low-sugar content, with no specific mention of the glycemic index. Potatoes, whole wheat bread, and specific high-fiber, moderate-to-high–glycemic index breakfast cereals were recommended. During clinic visits, the dietitian referred to the diets as the “low–glycemic index diet” or the “high-fiber/low-sugar” diet. Participants were provided with a booklet outlining the CHO choices as well as the CHO food amounts constituting one serving (based on 15-g portions). To assist with achieving stable blood glucose levels throughout the day, participants were advised to consume three small meals and two to three snacks with a specified number of servings of CHOs."ModeratelyNo differences in gestational weight gain or birth outcomes. Women on the low-glycemic-index diet were less likely to require insulin.
4Rizkalla et al. 2004Improved Plasma Glucose Control, Whole-Body Glucose Utilization, and Lipid Profile on a Low-Glycemic Index Diet in Type 2 Diabetic Men12 men with type 2 diabetes4 weeksLow-glycemic-index vs. high-glycemic-index diet"The diet in the two experimental periods consisted of ordinary food items. In the LGI period, carbohydrate items with a GI lower than 45 was recommended, whereas foods with a GI higher than 60 were recommended in the HGI period (glucose = 100). This was accomplished by providing a list to each individual of the recommended daily intake of commonly used foods and a substitution list allowing exchanges within food groups. During the LGI period, patients were advised to consume pumpernickel, pasta, lentils, haricot beans, chickpeas, and mung beans, whereas during the HGI diet, they were asked to consume wholemeal bread, French baguettes, potatoes, and rice (white, cooked)."UnclearLow-glycemic-index diet improved fasting glucose, HbA1c, and insulin sensitivity. No impact on weight or fat mass.Fiber intake was higher on the low-GI diet
5Smith et al. 2007A low-glycemic-load diet improves symptoms in acne vulgaris patients: a randomized controlled trial43 adolescent and young adult men12 weeks
Low-glycemic-load vs. high-carbohydrate control diet
"The LGL group was instructed to substitute high-GI foods with foods higher in protein (eg, lean meat, poultry, or fish) or with foods with a lower GI (eg, whole-grain bread, pasta, and fruit). Some staple foods were supplied, and the participants were urged to consume these or similar foods daily. Each participant received individualized dietary plans that were isocalorically matched with their baseline diet as determined from 7-d weighed and measured food records. The recommended LGL diet consisted of 25% of energy from protein, 45% from low-GI carbohydrates, and 30% energy from fats. In contrast, the control group received carbohydrate-dense staples and were instructed to eat these or similar foods daily. The foods provided had moderate-to-high GI values and were typical of their normal diet as evidenced from 7-d weighed and measured food records. The control group was not informed about the GI, but were urged to include carbohydrates as a regular part of their diet. "NoLow-glycemic-load diet led to a greater decrease in acne, weight, and fasting insulin
Low-glycemic-load diet was much higher in protein and fiber
6Sichieri et al. 2007An 18-mo randomized trial of a low-glycemic-index diet and weight change in Brazilian women203 healthy women18 monthsLow-glycemic-index vs. high-glycemic-index diet"Dietary counseling was based on a small energy restriction (ie, 100–300 kcal), and skipping the diet 1 d/wk was allowed. Individual nutritionist counseling every month with menus and exchange lists was provided. Both diets were designed with 26–28% of energy as fat. For each meal (Table 1), the LGI diets were designed to maintain an average difference of 40 GI units compared with the HGI diet. Calculations were based on published GI values for healthy individuals (10), with white bread as the standard GI of 100%. The overall GI was calculated by multiplying the carbohydrate intake of each food by its GI, summing up the products for all foods and dividing the sum by the total carbohydrate intake. Because sticky rice versus parboiled rice was one of the major determinants of the difference in GI between the 2 diets, beyond the amount of beans, we determined the hydrolysis of the most-reported brand of rice consumed by the women via vitro hydrolysis analysis (11) (Figure 2). The difference in GI between the 2 types of rice (≈25%) was of a magnitude similar to GI values previously reported (116 compared with 91, with white bread as reference) (10). In vitro analyses were also conducted for foods commonly used in Brazil for which no GI was available, such as okra, guava, cheese bread, and manioc bread."ModeratelyNo difference in weight at 18 months. Greater reduction in triglycerides and VLDL in the low-glycemic-index group.Different types of rice were a major determinant of different GI/GLs. 40% dropout at 18 months.
7Wolever et al. 2008The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein162 men and women with mild type 2 diabetes12 monthsHigh-carbohydrate, high-glycemic-index, high-carbohydrate, low-glycemic-index, or low-carbohydrate, high-monounsaturated-fat diets"The dietary intervention called for in the study protocol was for subjects to consume specific key foods, which, by themselves, would result in the desired changes in nutrient intake. Subjects in each diet group could choose from 16–21 key foods (Table 1), which were provided free of charge. Choices could vary throughout the study period, and intake was recorded daily in key-food diaries. For the high- and low-GI diets, the key foods were starchy carbohydrates whose GI we had determined (24–29). The amount prescribed was such that their carbohydrates provided 20–25% of the energy requirement estimated by using the tables of the Lipid Research Clinics (30) to which 300 kcal/d was added for exercise (31) and from which 500 kcal/d was subtracted if the subject wished to lose weight. We expected this intervention to result in a GI difference of ≈10 between the high-GI and low-GI diets (32). For the low-CHO diet, key foods consisted of olive or canola oils or spreads, nuts, and other foods low in SFAs and high in MUFAs and known to be associated with reduced risks of diabetes and CVD (33–35) or known to reduce blood lipids (16, 36, 37). These foods replaced carbohydrate foods normally consumed and were prescribed in amounts sufficient to raise total fat intake by ≈10%... For subjects randomly assigned to the high-GI diet, the advice focused on following a healthy low-fat diet and avoiding low-GI foods. Subjects randomly assigned to the low-GI diet were given low-fat diet advice along with suggestions about to how to exchange high-GI foods for low-GI foods. Subjects randomly assigned to the low-CHO diet were given advice about how to reduce SFA intake and how to exchange carbohydrate-rich foods for the study key foods high in MUFAs. All subjects were given a list of the key foods for their respective study diet, and the list indicated the number of servings they were to consume each day. Subjects were advised on how to incorporate the key foods into their diet in exchange for others so as to avoid weight gain."NoNo differences in weight or HbA1c. Fasting glucose was higher, but OGTT glucose was lower, after the low-glycemic-index dietFiber intake was higher on the low-GI diet
8Louie et al. 2011A Randomized Controlled Trial Investigating the Effects of a Low–Glycemic Index Diet on Pregnancy Outcomes in Gestational Diabetes Mellitus99 women with gestational diabetes4-10 weeksLow-glycemic-index vs. moderate-glycemic-index high-fiber diet"Subjects were randomized to one of two healthy diets of similar protein (15–25%), fat (25–30%), and carbohydrate (40–45%) content-- one with an LGI (target GI #50) and the other with a high-fiber content and moderate GI, similar to the Australian population average (HF) (target GI ;60) (13–15). Both study diets provided all essential nutrients for pregnancy other than iron and iodine, which were supplemented as appropriate by the treating endocrinologist. The baseline 3-day food diary provided information on baseline dietary composition and served as the basis of individualized dietary counseling."ModeratelyNo differences in pregnancy outcomes or insulin requirements
9Ma et al. 2008A randomized clinical trial comparing low–glycemic index versus ADA dietary education among individuals with type 2 diabetes40 men and women with poorly controlled type 2 diabetes12 monthsLow-glycemic-index diet vs. American Diabetes Association dietSee table 2. Description of diets is general with few specifics. "Briefly, the ADA diet includes carbohydrate counting, and entails following the Medical Nutrition Therapy Guidelines from the ADA [8,9,13]. The ADA recommends that total daily carbohydrate should be based on the participant’s estimated caloric needs, with a goal of consuming an average of 55% total energy from carbohydrate sources. In contrast, patients on the low-GI diet were educated on how to choose predominantly low-GI foods with efforts to tailor the integration of GI foods to the patient’s lifestyle and taste preferences through substitutions, additions, and directed changes."NoSimilar reductions in HbA1c, weight loss, and metabolic markers. Subjects on the low-glycemic-index diet were less likely to begin or increase insulin dosage.Low-glycemic-index diet was higher in protein
10McMillan-Price et al. 2006Comparison of 4 Diets of Varying Glycemic Load on Weight Loss and Cardiovascular Risk Reduction in Overweight and Obese Young Adults129 overweight or obese young adults12 weeksFour different diets: High-carbohydrate high-glycemic-index, high-carbohdyrate low-glycemic-index, high-protein high-glycemic-index, and high-protein low-glycemic-index. The glycemic load was highest in diet 1 and lowest in diet 4."All 4 diets were designed as reduced-energy, reduced-fat (30% E), moderate-fiber (30 g/d) eating plans with differences in the quantity and quality of available CHOs. Diet 1 was a high-CHO (55% E) and average-protein (15% E) diet based on high-GI whole grains, including fiber-rich breakfast cereals and breads. Diet 2 had the same macronutrient proportions but was based on previously verified low-GI foods.17 Diet 3 was a higher-protein (25% E), CHO-reduced (45% E) diet based on lean red meat and high-GI CHO whole grains. Diet 4 had the same macronutrient proportions as diet 3 but specified low-GI CHO choices. The target GL (GI × CHO content), calculated as the sum of foods in sample menus, was highest in diet 1 and lowest in diet 4 (Table 2). Subjects were given eating plans that were devised to help them lose weight (providing approximately 1400 kcal [6000 kJ] for women and 1900 kcal [8000 kJ] for men) and achieve the desired macronutrient distribution. These plans specified the number of servings from each food group and suitable choices within each group. Additional lists of appropriate meals and snacks were also provided. Dairy intake was held constant to minimize confounding from this source. To allow satiety and appetite factors to function, subjects were told to “eat to appetite” but were not required to consume all specified servings and, if hungry, were permitted to increase the number of servings proportionately from each food group. To maximize compliance, all key CHO and protein foods and some preprepared meals were provided. A color-coded “shop” system (different color for each diet) with bar code reader was used, and subjects collected foods of low or high GI (eg, bread, breakfast cereal, crackers, snack bars, oats, legumes, pasta, and basmati or jasmine rice), red meat portions, and specially prepared frozen meals each week.NoNo consistent impact of glycemic load on weight loss, fat loss, or metabolic biomarkers.The high-carbohydrate low-glycemic-index diet group ate more fiber than the other groups
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