The American journal of clinical nutrition
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Interest in the glycemic impact of diet on health and well-being is growing among health care professionals and consumers. Diets with high glycemic impact have been postulated to increase risk of obesity, insulin resistance, diabetes, and cardiovascular disease. A reduction in the glycemic impact of the diet has been proposed as a means of assisting body weight management, improving blood glucose control, and reducing diabetic, cardiovascular, and related risks. ⋯ Yet, a scientific debate exists about whether a relation between the glycemic response to diet and health truly exists, and, if so, which descriptor of a food's glycemic properties best predicts its effect on health outcomes. This article reports the proceedings of a workshop at which a meta-analysis of the relation between the glycemic response to foods and health was presented and the merits of glycemic index (GI), glycemic load (GL), and glycemic glucose equivalent as predictors of health outcomes were discussed. The conclusions include the findings that many studies purporting to investigate lower GI interventions actually studied lower GL interventions; that unavailable carbohydrate (eg, dietary fiber), independent of GI, seems to have at least as big an effect on health outcome as GI itself; that lower GI and GL diets are beneficial for health in persons with impaired glucose metabolism, but that it is as yet unclear what they mean for healthy persons; and that the larger the divergence of glucose metabolism from the norm, the larger the effect of lower GI and GL interventions.
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Review
Role of glycemic index and glycemic load in the healthy state, in prediabetes, and in diabetes.
The choice of carbohydrate-rich foods in the habitual diet should take into account not only their chemical composition but also their ability to influence postprandial glycemia (glycemic index). Fiber-rich foods generally have a low glycemic index (GI), although not all foods with a low GI necessarily have high fiber content. Several beneficial effects of low-GI, high-fiber diets have been shown, including lower postprandial glucose and insulin responses, an improved lipid profile, and, possibly, reduced insulin resistance. ⋯ In relation to prevention of cardiovascular disease, intervention studies evaluating the effect of a low-GI diet on clinical events are not available; moreover, the results of the few available intervention studies evaluating the effects of GI on the cardiovascular disease risk factor profile are not always concordant. The best evidence of the clinical usefulness of GI is available in diabetic patients in whom low-GI foods have consistently shown beneficial effects on blood glucose control in both the short-term and the long-term. In these patients, low-GI foods are suitable as carbohydrate-rich choices, provided other attributes of the foods are appropriate.
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Islet dysfunction and peripheral insulin resistance are both present in type 2 diabetes and are both necessary for the development of hyperglycemia. In both type 1 and type 2 diabetes, large, prospective clinical studies have shown a strong relation between time-averaged mean values of glycemia, measured as glycated hemoglobin (HbA1c), and vascular diabetic complications. These studies are the basis for the American Diabetes Association's current recommended treatment goal that HbA1c should be <7%. ⋯ Interventional studies indicate that reducing postmeal glucose excursions is as important as controlling fasting plasma glucose in persons with diabetes and impaired glucose tolerance. Evidence exists for a causal relation between postmeal glucose increases and microvascular and macrovascular outcomes; therefore, it is not surprising that treatment with different compounds that have specific effects on postprandial glucose regulation is accompanied by a significant improvement of many pathways supposed to be involved in diabetic complications, including oxidative stress, endothelial dysfunction, inflammation, and nuclear factor-kappaB activation. The goal of therapy should be to achieve glycemic status as near to normal as safely possible in all 3 components of glycemic control: HbA1c, fasting glucose, and postmeal glucose peak.
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Randomized Controlled Trial
Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum.
Altering the macronutrient composition of the diet influences hunger and satiety. Studies have compared high- and low-protein diets, but there are few data on carbohydrate content and ketosis on motivation to eat and ad libitum intake. ⋯ In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets.
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Randomized Controlled Trial
The effects of a whole grain-enriched hypocaloric diet on cardiovascular disease risk factors in men and women with metabolic syndrome.
Whole-grain foods are associated in observational studies with a lower body mass index and lower cardiovascular disease (CVD) risk. However, few clinical trials have tested whether incorporating whole grains into a hypocaloric diet increases weight loss and improves CVD risk factors. ⋯ Both hypocaloric diets were effective means of improving CVD risk factors with moderate weight loss. There were significantly (P<0.05) greater decreases in CRP and percentage body fat in the abdominal region in participants consuming whole grains than in those consuming refined grains.