High-glycemic index foods, hunger, and obesity: is there a connection?

Overweight among low-income preschool children associated with the consumption of sweet drinks: Missouri, 1999-2002

OBJECTIVE

To examine the association between sweet drink consumption and overweight among preschool children.

METHODS

A retrospective cohort design was used to examine the association between sweet drink consumption and overweight at follow-up among 10904 children who were aged 2 and 3 years and had height, weight, and Harvard Service Food Frequency Questionnaire data collected between January 1999 and December 2001 and height and weight data collected 1 year later. Sweet drinks included vitamin C-containing juices, other juices, fruit drinks, and sodas as listed on the Harvard Service Food Frequency Questionnaire. Logistic regression was used to adjust for age; gender; race/ethnicity; birth weight; and intake of high-fat foods, sweet foods, and total calories. Results were stratified by baseline BMI.

RESULTS

Among children who were normal or underweight at baseline (BMI <85th percentile), the association between sweet drink consumption and development of overweight was positive but not statistically significant. Children who were at risk for overweight at baseline (BMI 85th-<95th percentile) and consumed 1 to <2 drinks/day, 2 to <3 drinks/day, and > or =3 drinks/day were, respectively, 2.0 (95% confidence interval [CI]: 1.3-3.2), 2.0 (95% CI: 1.2-3.2), and 1.8 (95% CI: 1.1-2.8) times as likely to become overweight as the referent (<1 drink/day). Children who were overweight at baseline (BMI > or =95th percentile) and consumed 1 to <2 drinks/day, 2 to <3 drinks/day, and > or =3 drinks/day were, respectively, 2.1, 2.2, and 1.8 times as likely to remain overweight as the referent.

CONCLUSIONS

Reducing sweet drink consumption might be 1 strategy to manage the weight of preschool children. Additional studies are needed to understand the mechanism by which such consumption contributes to overweight.

Diet, insulin resistance, and obesity: zoning in on data for Atkins dieters living in South Beach

Insulin resistance is a central pathogenic factor for the metabolic syndrome and is associated with both generalized obesity and the accumulation of fat in the omental and intramyocellular compartments. In the context of the current obesity epidemic, it is imperative to consider diets in terms of their ability to both promote weight loss and ameliorate insulin resistance. Weight loss under any dietary formulation depends on hypocaloric intake, and only moderate weight loss (5-10%) is sufficient to augment insulin sensitivity. However, increments in insulin sensitivity may be more directly related to loss of intramyocellular or omental fat rather than loss of total body weight per se. The widespread acceptance of popular low-carbohydrate high-fat diets (e.g. Atkins Diet, Zone Diet, South Beach diet) further underscores the need to evaluate dietary interventions regarding their safety and metabolic effects. These high-fat diets have been shown to be safe in the short term; however, their long-term safety has not been established. With respect to insulin sensitivity, diets enriched in saturated fats can induce insulin resistance, whereas fat substitution with monounsaturated fats can enhance insulin sensitivity. On the other hand, high-fiber, high-carbohydrate diets comprised of foods with low caloric density can similarly be used for effective weight reduction and to ameliorate insulin resistance. Although some data suggest that low-glycemic index diets are most advantageous in this regard, these effects may have more to do with increments in dietary fiber than differences in available carbohydrates. Popular low-carbohydrate, high-fat diets are being fervently embraced as an alternative to challenging modifications in lifestyle and intentional calorie reduction. Current data do not support such unbridled enthusiasm for these diets, particularly in relationship to high-fiber, high-carbohydrate diets emphasizing intake of fresh vegetables and fruits. Long-term studies to determine the efficacy and safety of both popular and experimental diets are warranted.

Ballaststoffe: Mehr als ein Diätmittel

A nutrition rich in fibre has a preventive effect against constipation, colon diverticulosis, carcinoma of the large bowel and stomach, type 2-diabetes, metabolic syndrome and cardiovascular disease. In case of constipation, diverticulosis and diabetes this effect solely depends on dietary fibre. Regarding carcinomas and cardiovascular diseases, so far unknown factors integrated in or associated with fibre-rich food may also contribute to the preventive effect. Therapy with dietary fibre is indicated for constipation, colon diverticulosis, diarrhea, diabetes, and hypercholesterinemia. The individual dietary fibres differ substance-specifically. Food-integrated dietary fibre such as whole-grain bread, vegetables and fruit have their place in prevention. Dietary fibre preparations such as wheat bran, flax seed or sugar-beet fibre are useful in the treatment of constipation, colon diverticulosis and adiposity. Oat bran is preferentially used in hypercholesterinemia. Purified dietary fibres such as cellulose, guar, psyllium, and beta-glucan have an anti-diabetic, all viscous fibres an anti-lipaemic effect. The therapeutic dosages of dietary fibre preparations are 20-40 g/day and of purified fibres substances 10-20 g/day respectively.

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

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.

Diet, nutrition and the prevention of excess weight gain and obesity

OBJECTIVES

To review the evidence on the diet and nutrition causes of obesity and to recommend strategies to reduce obesity prevalence.

DESIGN

The evidence for potential aetiological factors and strategies to reduce obesity prevalence was reviewed, and recommendations for public health action, population nutrition goals and further research were made.

RESULTS

Protective factors against obesity were considered to be: regular physical activity (convincing); a high intake of dietary non-starch polysaccharides (NSP)/fibre (convincing); supportive home and school environments for children (probable); and breastfeeding (probable). Risk factors for obesity were considered to be sedentary lifestyles (convincing); a high intake of energy-dense, micronutrient-poor foods (convincing); heavy marketing of energy-dense foods and fast food outlets (probable); sugar-sweetened soft drinks and fruit juices (probable); adverse social and economic conditions-developed countries, especially in women (probable). A broad range of strategies were recommended to reduce obesity prevalence including: influencing the food supply to make healthy choices easier; reducing the marketing of energy dense foods and beverages to children; influencing urban environments and transport systems to promote physical activity; developing community-wide programmes in multiple settings; increased communications about healthy eating and physical activity; and improved health services to promote breastfeeding and manage currently overweight or obese people.

CONCLUSIONS

The increasing prevalence of obesity is a major health threat in both low- and high income countries. Comprehensive programmes will be needed to turn the epidemic around.

What Can Intervention Studies Tell Us about the Relationship between Fruit and Vegetable Consumption and Weight Management?

Given the recent surge in obesity, effective dietary strategies for weight management are required. Because fruits and vegetables are high in water and fiber, incorporating them in the diet can reduce energy density, promote satiety, and decrease energy intake. Although few interventions have specifically addressed fruit and vegetable consumption, evidence suggests that coupling advice to increase intake of these foods with advice to decrease energy intake is a particularly effective strategy for weight management. This approach may facilitate weight loss because it emphasizes positive messages rather than negative, restrictive messages.

Prospective study of the association of changes in dietary intake, physical activity, alcohol consumption, and smoking with 9-y gain in waist circumference among 16 587 US men

BACKGROUND

Although it is known that abdominal obesity increases the risk of chronic diseases, prospective data examining the relation between lifestyle factors and the accumulation of abdominal adipose tissue are sparse.

OBJECTIVE

The objective of the study was to determine the associations of changes in diet, physical activity, alcohol consumption, and smoking with 9-y waist gain among US men.

DESIGN

A prospective cohort comprised 16 587 US men aged 40-75 y at baseline in 1986. Data on lifestyle factors were provided periodically with the use of self-reported questionnaires, and participants measured and reported their waist circumference in 1987 and 1996.

RESULTS

In multivariate analyses, a 2% increment in energy intake from trans fats that were isocalorically substituted for either polyunsaturated fats or carbohydrates was significantly associated with a 0.77-cm waist gain over 9 y (P < 0.001 for each comparison). An increase of 12 g total fiber/d was associated with a 0.63-cm decrease in waist circumference (P < 0.001), whereas smoking cessation and a 20-h/wk increase in television watching were associated with a 1.98-cm and 0.59-cm waist gain, respectively (P < 0.001). Increases of 25 metabolic equivalent tasks (METs) * h/wk in vigorous physical activity and of >/= 0.5 h/wk in weight training were associated with 0.38-cm and 0.91-cm decreases in waist circumference, respectively (P < 0.001 for each comparison). These associations remained significant after further adjustment for concurrent change in body mass index. Changes in total fat and alcohol consumption and in walking volume were not significantly related to waist gain.

CONCLUSIONS

Waist gain may be modulated by changes in trans fat and fiber consumption, smoking cessation, and physical activity.

Consumption of sugars and the regulation of short-term satiety and food intake

This review examines the relation between the consumption of sugars and their effects on short-term (ie, to 2 h) satiety and food intake in humans. Many factors need to be considered in the evaluation of reported studies and the conclusions derived from this body of literature. These factors include evaluation of the dose and form (solid or liquid) of the treatments, time of day administered, characteristics of the subjects, sample size, and approaches used to measure satiety and food intake. Mechanisms by which sugars may signal regulatory systems for food intake need to be considered when evaluating both study designs and conclusions. For this reason, the relation between the blood glucose response to sugar consumption and subsequent feeding behavior is also examined. It is concluded that sugars stimulate satiety mechanisms and reduce food intake in the short term and that the mechanisms by which this response occurs cannot be attributed solely to their effect on blood glucose.

Plant-based foods and prevention of cardiovascular disease: an overview

Evidence from prospective cohort studies indicates that a high consumption of plant-based foods such as fruit and vegetables, nuts, and whole grains is associated with a significantly lower risk of coronary artery disease and stroke. The protective effects of these foods are probably mediated through multiple beneficial nutrients contained in these foods, including mono- and polyunsaturated fatty acids, n-3 fatty acids, antioxidant vitamins, minerals, phytochemicals, fiber, and plant protein. In dietary practice, healthy plant-based diets do not necessarily have to be low in fat. Instead, these diets should include unsaturated fats as the predominant form of dietary fat (eg, fats from natural liquid vegetable oils and nuts), whole grains as the main form of carbohydrate, an abundance of fruit and vegetables, and adequate n-3 fatty acids. Such diets, which also have many other health benefits, deserve more emphasis in dietary recommendations to prevent chronic diseases.

Effect of two breakfasts, different in carbohydrate composition, on hunger and satiety and mood in healthy men

OBJECTIVE

To study the effect of simple vs complex carbohydrates (SCHO and CCHO respectively) containing breakfasts on blood parameters, hunger and satiety and mood.

DESIGN

A 2-day, open, randomised, cross-over trial.

SUBJECTS

A total of 26 male subjects (34+/-6 y; BMI 23.4+/-2.2 kg m(-2)).

MEASUREMENTS

Blood glucose, insulin, triacylglycerols (TG), free fatty acids (FFA) and cholecystokinin (CCK) were determined repeatedly for 4 h on both test days after a breakfast containing SCHO or CCHO. Feelings of hunger and satiety were determined at similar time points as well. Mood state was examined 3 h after breakfast consumption.

RESULTS

Consumption of a SCHO breakfast resulted in higher glucose and insulin levels at 30 min after breakfast consumption. TG at 180 min, and FFA at 180 and 240 min were higher after SCHO breakfast than after CCHO breakfast. Satiety scores were higher after CCHO breakfast consumption for the first 90 min after intake. Furthermore, the item 'fatigue' was scored higher after SCHO breakfast than after CCHO breakfast intake.

CONCLUSION

Consumption of a CCHO breakfast is favourable in comparison to a SCHO breakfast, because of the lower perception of 'fatigue' and the higher degree of satiety after consumption.

Dieting, perceived deprivation, and preoccupation with food

A prospective study using 14-day food diaries was conducted to determine whether perceived deprivation and preoccupation with food correspond to actual caloric and fat intake, using a sample of 121 adult women who were binge eating without purging or were currently dieting. Caloric and fat intake were not significantly related to perceived deprivation. Only weight cycling and Revised Restraint Scale was significantly correlated with perceived deprivation with 11% of the variation explained by the Revised Restraint Scale scores. These findings support the contention that psychological deprivation occurs regardless of caloric intake. For preoccupation with food, only fat intake and Revised Restraint Scale scores were significantly correlated with 15% of the variance explained by the Revised Restraint Scale scores.

Effects of sugar intake on body weight: a review

Weight reduction programmes are mainly focused on reducing intake of fat and sugar. In this review we have evaluated whether the replacement of dietary (added) sugar by low-energy sweeteners or complex carbohydrates contributes to weight reduction. In two experimental studies, no short-term differences in weight loss were observed after use of aspartame as compared to sugar in obese subjects following a controlled energy-restricted diet. However, consumption of aspartame was associated with improved weight maintenance after a year. In two short-term studies in which energy intake was not restricted, substitution of sucrose by artificial sweeteners, investigated mostly in beverages, resulted in lower energy intake and lower body weight. Similarly, two short-term studies, comparing the effect of sucrose and starch on weight loss in obese subjects did not find differences when the total energy intake was equal and reduced. An ad libitum diet with complex carbohydrates resulted in lower energy intake compared to high-sugar diets. In two out of three studies, this was reflected in lower body weight in subjects consuming the complex carbohydrate diet. In conclusion, a limited number of relatively short-term studies suggest that replacing (added) sugar by low-energy sweeteners or by complex carbohydrates in an ad libitum diet might result in lower energy intake and reduced body weight. In the long term, this might be beneficial for weight maintenance. However, the number of studies is small and overall conclusions, in particular for the long term, cannot be drawn.

Similar effects of foods high in protein, carbohydrate and fat on subsequent spontaneous food intake in healthy individuals

Pre-loads high in protein, as compared to carbohydrate and fat, produce greater satiety and reduce food intake after a fixed time interval. This study investigated the effect of macronutrient composition on spontaneous eating behaviour. On four separate occasions, 16 fasted, healthy, non-obese men, blinded to the true purpose of the study, consumed iso-energetic ( approximately 3MJ) yoghurt-based pre-loads of equivalent weight ( approximately 0.5 kg), high in fat (40%) [HF], carbohydrate (60%) [HC] or protein (29%) [HP], and no pre-load in a randomized, single-blind fashion. Subjects ate at will from a selection of food items for the remainder of the day (7 h) with the time of food requests (h) and energy content (kJ) and macronutrient distribution (%) of food eaten recorded. The three pre-loads delayed the first spontaneous request for food by 1.5-1.8 h relative to no pre-load. Total spontaneous food intake was suppressed 29% [HP], 20% [HF] and 17% [HC] by the pre-loads. Neither the amount of food eaten per spontaneous eating episode, nor the spontaneous eating frequency differed statistically following ingestion of the different pre-loads or no pre-load. In this study, in subjects who were free to choose when as well as how much they ate, a high-protein pre-load exerted similar effects on satiety as did iso-energetic high-fat and high-carbohydrate pre-loads.

Overweight and obesity in women: health risks and consequences

The evidence for the adverse effects of obesity on women's health is overwhelming and indisputable. Obesity, especially abdominal obesity, is central to the metabolic syndrome and is strongly related to polycystic ovary syndrome (PCOS) in women. Obese women are particularly susceptible to diabetes, and diabetes, in turn, puts women at dramatically increased risk of cardiovascular disease (CVD). Obesity substantially increases the risk of several major cancers in women, especially postmenopausal breast cancer and endometrial cancer. Overweight and obesity are associated with elevated mortality from all causes in both men and women, and the risk of death rises with increasing weight. Curbing the twin epidemics of obesity and diabetes calls for not only changes in diet and lifestyle at individual levels but also changes in policy, physical and social environment, and cultural norms.

Weight loss associated with a daily intake of three apples or three pears among overweight women

OBJECTIVE

We investigated the effect of fruit intake on body weight change.

METHODS

Hypercholesterolemic, overweight (body mass index > 25 kg/m2), and non-smoking women, 30 to 50 y of age, were randomized to receive, free of charge, one of three dietary supplements: apples, pears, or oat cookies. Women were instructed to eat one supplement three times a day in a total of six meals a day. Participants (411 women) were recruited at a primary care center of the State University of Rio de Janeiro, Brazil. Fifty-one women had fasting blood cholesterol levels greater than 6.2 mM/L (240 mg/dL) and 49 were randomized. Subjects were instructed by a dietitian to eat a diet (55% of energy from carbohydrate, 15% from protein, and 30% from fat) to encourage weight reduction at the rate of 1 kg/mo.

RESULTS

After 12 wk of follow-up, the fruit group lost 1.22 kg (95% confidence interval = 0.44-1.85), whereas the oat group had a non-significant weight loss of 0.88 kg (0.37-2.13). The difference between the two groups was statistically significant (P = 0.004). To explore further the body weight loss associated with fruit intake, we measured the ratio of glucose to insulin. A significantly greater decrease of blood glucose was observed among those who had eaten fruits compared with those who had eaten oat cookies, but the glucose:insulin ratio was not statistically different from baseline to follow-up. Adherence to the diet was high, as indicated by changes in serum triacylglycerols, total cholesterol, and reported fruit intake. Fruit intake in the oat group throughout treatment was minimal.

CONCLUSIONS

Intake of fruits may contribute to weight loss.

Whole grain consumption and weight gain: a review of the epidemiological evidence, potential mechanisms and opportunities for future research

The epidemiological data that directly examine whole grain v. refined grain intake in relation to weight gain are sparse. However, recently reported studies offer insight into the potential role that whole grains may play in body-weight regulation due to the effects that the components of whole grains have on hormonal factors, satiety and satiation. In both clinical trials and observational studies the intake of whole-grain foods was inversely associated with plasma biomarkers of obesity, including insulin, C-peptide and leptin concentrations. Whole-grain foods tend to have low glycaemic index values, resulting in lower postprandial glucose responses and insulin demand. High insulin levels may promote obesity by altering adipose tissue physiology and by enhancing appetite. The fibre content of whole grains may also affect the secretion of gut hormones, independent of glycaemic response, that may act as satiety factors. Future studies may examine whether whole grain intake is directly related to body weight, and whether the associations are primarily driven by components of the grain, including dietary fibre, bran or germ.

A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women

Claims about the merits or risks of carbohydrate (CHO) vs. protein for weight loss diets are extensive, yet the ideal ratio of dietary carbohydrate to protein for adult health and weight management remains unknown. This study examined the efficacy of two weight loss diets with modified CHO/protein ratios to change body composition and blood lipids in adult women. Women (n = 24; 45 to 56 y old) with body mass indices >26 kg/m(2) were assigned to either a CHO Group consuming a diet with a CHO/protein ratio of 3.5 (68 g protein/d) or a Protein Group with a ratio of 1.4 (125 g protein/d). Diets were isoenergetic, providing 7100 kJ/d, and similar amounts of fat ( approximately 50 g/d). After consuming the diets for 10 wk, the CHO Group lost 6.96 +/- 1.36 kg body weight and the Protein Group lost 7.53 +/- 1.44 kg. Weight loss in the Protein Group was partitioned to a significantly higher loss of fat/lean (6.3 +/- 1.2 g/g) compared with the CHO Group (3.8 +/- 0.9). Both groups had significant reductions in serum cholesterol ( approximately 10%), whereas the Protein Group also had significant reductions in triacylglycerols (TAG) (21%) and the ratio of TAG/HDL cholesterol (23%). Women in the CHO Group had higher insulin responses to meals and postprandial hypoglycemia, whereas women in the Protein Group reported greater satiety. This study demonstrates that increasing the proportion of protein to carbohydrate in the diet of adult women has positive effects on body composition, blood lipids, glucose homeostasis and satiety during weight loss.

Sedentary lifestyle and risk of obesity and type 2 diabetes

Obesity and type 2 diabetes have reached epidemic proportions in the United States. It is well-established that increasing physical activity plays an important role in reducing risk of obesity and diabetes. Few studies, however, have examined the association between sedentary behaviors such as prolonged television (TV) watching and obesity and diabetes. Using data from a large prospective cohort study, the Health Professionals' Follow-up Study, we have demonstrated that increasing TV watching is strongly associated with obesity and weight gain, independent of diet and exercise. Also, prolonged TV watching is associated with a significantly increased risk of type 2 diabetes. Men who watched TV more than 40 h per week had a nearly threefold increase in the risk of type 2 diabetes compared with those who spent less than 1 h per week watching TV. The increased risk was not entirely explained by the decreased physical activity and unhealthy eating patterns associated with TV watching. Thus, public health campaigns to reduce the risk of obesity and type 2 diabetes should promote not only increasing exercise levels but also decreasing sedentary behaviors, especially prolonged TV watching.

Dietary assessment tools for developing countries for use in multi-centric, collaborative protocols

In recent years, increasing interest in the format of multi-centric studies among different populations in developing nations has evolved in the field of health surveys and epidemiology. Dietary intake data are most often part of these cross-cultural and cross-national collaborative efforts. Various questions have been raised about the appropriate endeavours for dietetics and nutritional sciences in developing societies, the instruments available for application, and the pitfalls and caveats in their use. An important consideration is that studies be hypothesis-driven and not mere 'fishing expeditions' of unfocused data gathering. All known dietary intake measurement tools are within the preview of developing country research, but they often must be adapted individually and differentially to suit a given population. In a multi-centric context, this is complicated. The watchword should be collecting comparable information across sites, not using identical approaches. Choice of dietary intake measurement tools must be honed to the hypotheses and assumptions, on the one hand, and the exigencies and pitfalls of working in the developing country milieu, in which linguistics, seasonality, migration, uncommonness of food systems and ethical considerations present barriers and caveats, on the other. Within the hypotheses, the assumptions regarding the penetration of the measured exposures must be borne in mind. Multi-centre studies in developing countries have relevance and importance in the context of food security, diet and disease, eating behaviour and satiety regulation, and nutritional anthropology.

Biobehavioral influences on energy intake and adult weight gain

U.S. adults are now gaining more weight and becoming obese at an earlier age than in previous years. The specific causes of adult weight gain are unknown, but may be attributed to a combination of factors leading to positive energy balance. U.S. food supply data indicate that Americans have had a gradual increase in energy intake since 1970, and that per capita energy intake was 1.42 MJ/d (340 kcal/d) higher in 1994 than that in 1984. In contrast, self-reported physical activity remained constant between 1990 and 1998. Taken together, these data indicate that the increasing trend in U.S. adult weight gain is primarily attributable to overconsumption of energy. Epidemiological and experimental studies in animals and humans provide strong evidence that biobehavioral factors such as dietary variety, liquid (vs. solid) energy, portion size, palatability (taste), snacking patterns, restaurant and other away-from-home food, and dietary restraint and disinhibition influence hunger, satiety and/or voluntary energy intake. When these eating behaviors are consistently experienced either separately or in combination over the long term, they are likely to facilitate overeating. We provide a brief overview of the evidence to date for the role of these biobehavioral factors in contributing to excess energy intake and increases in body weight over time.

Should obese patients be counselled to follow a low-glycaemic index diet? No

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, and the diets are similar in all aspects except GI, has not yet been performed.

Inverse association between the effect of carbohydrates on blood glucose and subsequent short-term food intake in young men

BACKGROUND

A primary mechanism by which carbohydrates are thought to regulate satiety and food intake is through their effect on blood glucose.

OBJECTIVES

The objectives were to describe the effect of defined carbohydrate preloads on food intake and blood glucose and to determine the association between food intake and blood glucose.

DESIGN

Three experiments were conducted in which selected carbohydrates as 1255-kJ isovolumetric beverages were administered to young men after an overnight fast. Measurements of blood glucose and appetite were made at specified times during the next 60 min. Food intake was measured at 60 min.

RESULTS

Glucose resulted in the highest glycemic response, which was followed, in order, by the responses to polycose, sucrose, amylopectin, a fructose-glucose mixture, and amylose. The high-glycemic-index preloads (glucose, polycose, and sucrose) resulted in lower mealtime energy intake during a test meal at 1 h, but the low-glycemic-index preloads (amylose, amylopectin, and a fructose-glucose mixture) did not. An inverse relation was observed between the blood glucose concentrations in the area under the curve and the subjective appetite (r = -0.23, P < 0.05) and food intake at 60 min (r = -0.24, P < 0.05).

CONCLUSIONS

Food intake and subjective appetite are inversely associated with blood glucose response in the 60 min after consumption of carbohydrates. Carbohydrates with a high glycemic index (glucose, polycose, and sucrose) suppress subjective appetite and food intake in the short term, but those with a low glycemic index (amylose and amylopectin) do not.

Should obese patients be counselled to follow a low-glycaemic index diet? Yes

A reduction in dietary fat has been widely advocated for the prevention and treatment of obesity and related complications. However, the efficacy of low-fat diets has been questioned in recent years. One potential adverse effect of reduced dietary fat is a compensatory increase in the consumption of high glycaemic index (GI) carbohydrate, principally refined starchy foods and concentrated sugar. Such foods can be rapidly digested or transformed into glucose, causing a large increase in post-prandial blood glucose and insulin. Short-term feeding studies have generally found an inverse association between GI and satiety. Medium-term clinical trials have found less weight loss on high GI or high glycaemic load diets compared to low GI or low glycaemic load diets. Epidemiological analyses link GI to multiple cardiovascular disease risk factors and to the development of cardiovascular disease and type 2 diabetes. Physiologically orientated studies in humans and animal models provide support for a role of GI in disease prevention and treatment. This review examines the mechanisms underlying the potential benefits of a low GI diet, and whether such diets should be recommended in the clinical setting.

Maternal carbohydrate intake and pregnancy outcome

Experimental evidence indicates that the primary maternal environmental factor that regulates feto-placental growth is substrate delivery to the placental site, which is the product of maternal substrate levels and the rate of placental-bed blood flow. Thus, maternal factors which change either substrate level or flow alter feto-placental growth rate. The best-studied substrate in human pregnancy is glucose, and there is a direct relationship between maternal blood glucose levels and size at birth. Altering the type of carbohydrate eaten (high- v. low-glycaemic sources) changes postprandial glucose and insulin responses in both pregnant and non-pregnant women, and a consistent change in the type of carbohydrate eaten during pregnancy influences both the rate of feto-placental growth and maternal weight gain. Eating primarily high-glycaemic carbohydrate results in feto-placental overgrowth and excessive maternal weight gain, while intake of low-glycaemic carbohydrate produces infants with birth weights between the 25th and the 50th percentile and normal maternal weight gain. The calculated difference in energy retention with similar total energy intakes is of the order of 80,000 kJ. Preliminary information from subsequent metabolic studies indicates that the mechanisms involved include changes in: daily digestible energy requirements (i.e. metabolic efficiency), substrate utilization (glucose oxidation v. lipid oxidation), and insulin resistance and sensitivity. Thus, altering the source of maternal dietary carbohydrate may prove to be a valuable tool in the management of pregnancies at risk for anomalous feto-placental growth and for the prevention and/or treatment of obesity and insulin resistance in the non-pregnant state.

Dietary patterns and their associations with obesity in the Brazilian city of Rio de Janeiro

OBJECTIVE

To evaluate the dietary patterns of adults living in the city of Rio de Janeiro, Brazil and their associations with body mass index (BMI).

RESEARCH METHODS AND PROCEDURES

A survey was conducted in 1996 in a probabilistic sample of 2040 households. Weight and height were measured and food intake was based on an 80-item semi-quantitative food frequency questionnaire. Dietary patterns were identified through factor analysis.

RESULTS

More than one-third of the adult population (20 to 60 years old) was overweight (BMI = 25 to 29.9 kg/m(2)), and 12% were obese (BMI >or= 30 kg/m(2)). Three major dietary patterns were identified: mixed pattern when all food groups and items had about the same factor loading, except for rice and beans; one pattern that relies mainly on rice and beans, which was called a traditional diet; and a third pattern, termed a Western diet, where fat (butter and margarine) and added sugar (sodas) showed the highest positive loading and rice and beans were strong negative components. Among men, the Western diet also included deep-fried snacks and milk products with high positive values. The traditional diet was associated with lower risk of overweight/obesity in logistic models adjusted for dieting, age, leisure physical activity, and occupation (13% reduction in men and 14% reduction in women comparing the traditional and Western diets).

DISCUSSION

Factors contributing to the effects of the Brazilian traditional diet may include low-energy density, high-dietary fiber content, incorporation of low glycemic index foods such as beans, or a relatively low food variety.

Effect of sucrose and safflower oil preloads on short term appetite and food intake of young men

The effects of carbohydrate and fat on satiety have been examined primarily through meal composition studies. The purpose of this study was to compare the effects of pure sucrose and safflower oil, isovolumetric beverage preloads, on appetite (measured every 15 minutes by visual analogue scales) and food intake 60 minutes later. Young men consumed 0, 418, 836 and 1254 kJ of sucrose in the first two experiments and these same doses of safflower oil in the third. Finally, the largest doses of sucrose and safflower oil were compared. Sucrose, but not safflower oil, suppressed average appetite compared with control. In experiment 2, food intake was reduced (p<0.05) by 518 kJ after the 418 and 836 kJ preloads and by 1129 kJ after the 1254 kJ sucrose preload. Only the 1254 kJ dose of safflower oil significantly suppressed food intake by 480 kJ in the third experiment. When the 1254 kJ doses were compared directly, sucrose suppressed food intake by 653 kJ compared with control where as safflower oil did not. It is concluded that, in the short-term, sucrose produces a dose dependent reduction in appetite and food intake that is greater than that produced by safflower oil.

Carbohydrates, appetite and feeding behavior in humans

The view of carbohydrates in relation to obesity has changed over the past few decades from being conducive to overconsumption and weight gain to being protective. This article reviews the mechanisms by which carbohydrate is purported to protect against weight gain. Although carbohydrate is metabolized and stored in the body less efficiently than fat, when de novo lipogenesis is invoked on very high carbohydrate diets, the beneficial effect on energy balance is likely to be minimal when typical high fat Western diets are consumed. However, it has been suggested that high carbohydrate foods may influence energy balance by reducing food intake through greater satiety effects, reducing energy density and displacing fat from the diet-the fat-sugar seesaw effect. To date, there seem to be few differences between sugars and starches on satiety and energy intake, but few studies have examined this. Some reduced-fat, and, therefore, higher carbohydrate, foods are highly energy dense. High carbohydrate foods do not necessarily have a low energy density. Evidence from recent studies suggests that adding carbohydrate, and especially sugar, to the diet neither displaces fat from the diet nor protects against elevated energy intake. Although it is easier to overeat on high fat than low fat foods, simply replacing fat with carbohydrate in the diet may not be as protective against overconsumption as the energy density or fat-sugar seesaw arguments suggest.

Dietary energy density and weight regulation

Dietary energy density (ED) has been suggested as an important determinant of energy intake and, therefore, energy regulation. This review summarizes published studies on the effects of dietary ED on hunger, satiety, energy intake, and body weight in healthy individuals, and compares the relative effects of ED manipulated by dietary fat only, fat and fiber, water, and type of sweetener. In short-term studies, consumption of low-ED foods promotes satiety, reduces hunger, and decreases energy intake with no marked differences between different dietary manipulations used to change ED. In addition, low-ED diets promote moderate weight loss in long-term studies. In studies lasting longer than 6 months, weight loss was more than three times as great in individuals consuming diets both low in fat and high in fiber compared with diets only low in fat (-3.4 kg versus -1.0 kg). Combined, these studies suggest that diets low in fat and high in fiber may be the most effective low-ED diets for promoting weight loss. Further research is needed on the effects of dietary ED by changing water or sweetener content.