The metabolic syndrome is a cluster of disorders (obesity, dyslipidaemia, hyperinsulinaemia and hypertension) which individually or collectively lead to an increase in the risk of cardiovascular disease. Over the years it has been associated with endothelial dysfunction, raised markers of chronic inflammation, insulin resistance and clotting dysregulation. Studies have shown that the prevalence of the metabolic syndrome in adults over the age of 20 years to be 24%, with approximately 12 million adults within the United Kingdom fulfilling the criteria for diagnosis. Numbers of individuals with the metabolic syndrome continue to rise following population trends of increasing sedentary lifestyle, high calorie intake, smoking, and stress. Associated is an increase in obesity, type 2 diabetes, cardiac disease, stroke and death. The increase is such that we can no longer be complacent about how we address the metabolic syndrome or its associated components. The management of the metabolic syndrome is varied and includes alterations in diet, physical exercise, and oral medication. It is well documented that a 10% reduction in weight leads to reductions in lipid abnormalities, diabetes and diabetes-related deaths, other total morbidity and deaths. Many dietary regimens have been postulated to benefit not only weight gain but improve cardiovascular risk. To address this we investigated the effect three different diets (low fat; low carbohydrate, high fat; and low glycaemic load) had on the metabolic syndrome to assess whether it is the changes in dietary caloric or macronutrient intake, or overall weight loss that had the greater influences on those aspects of metabolic syndrome which could potentially reduce cardiovascular risk.

Doctor of Philosophy (PhD) / Introduction: The conventional approach to weight loss, recommended by almost all health authorities around the world, has been to reduce the total amount of fat in the diet and replace with carbohydrates. However, research trials using this approach have produced only modest results at best, and despite the active promotion of low fat eating and an apparent decline in fat consumption, rates of overweight and obesity have continued to climb. More recently low glycaemic index (GI) and high protein diets have become popular and are widely used by the public. However, only a small number of randomised controlled trials have been conducted and none directly comparing the two. Both approaches effectively reduce glycaemic load (GL) and aim to reduce post-prandial glycaemia and insulinaemia. This study aimed to evaluate the ability of diets with reduced GL to enhance the weight loss effects of a reduced-fat diet, to compare the two approaches of reducing GL on metabolic and anthropometric changes, and to investigate any benefit of combining both approaches to produce the lowest GL. Methods: We conducted a 12-week intervention in 129 overweight or obese young adults who were assigned to one of four diets with varying GL, protein, carbohydrate and GI, but similar fat (30% energy), fat type and fibre content. DIET 1 (highest GL) contained 55% E as carbohydrate; DIET 2 was a low-GI version of DIET 1; DIET 3 was a high protein diet with 25% E as protein; DIET 4 (lowest GL) was a low-GI version of DIET 3. The increase in protein in DIETS 3 and 4 came primarily from lean red meat. All key foods and some pre-prepared frozen meals were provided to maximise dietary compliance. Outcome measures were body weight, body fat, lean mass, waist circumference and the following blood parameters: total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerols (TAG), free fatty acids, C-reactive protein, fasting insulin, fasting glucose and leptin. Insulin resistance and β-cell function were assessed using homeostatic model assessment (HOMA) and the newer computer models HOMA2-insulin sensitivity and HOMA2-β-cell function. Results: While all groups lost similar amounts of weight (4.2 to 6.2% of initial weight, p=0.09), the proportion who lost >5% of body weight varied significantly by diet: 31%, 56%, 66% and 33% in groups 1, 2, 3 and 4 respectively (p=0.011). Differences were strongest in women (76% of the total group) who showed significant differences among groups in percentage weight change (-3.7 ± 0.6%, -5.7 ± 0.6%, -6.5 ± 0.5%, -4.1 ± 0.7% respectively, p=0.005) and fat loss (-3.1 ± 0.4kg, -4.9 ± 0.6kg, -4.8 ± 0.4kg, -3.6 ± 0.7kg respectively, p=0.007). Total and LDL-cholesterol increased on DIET 3 (high protein) compared to a fall on diet 2 (high carbohydrate/low-GI, p=0.013). TAG, HDL-cholesterol and glucose homeostasis improved on all four diets, with no effect of diet composition. Goals for energy distribution were not achieved exactly: both carbohydrate groups ate less fat and the diet 2 group ate more fibre. Conclusions: Reducing GL, through either substituting low-GI foods or replacing some carbohydrate with protein, improved the efficacy of a reduced-fat diet in women and in those with high TAG. Combining both approaches to produce the lowest GL did not promote further weight or body fat loss. Although weight loss was similar in all four diets for the group as a whole, overall clinical outcomes were superior on the high carbohydrate, low-GI diet.

Doctor of Philosophy (PhD) / Introduction: The conventional approach to weight loss, recommended by almost all health authorities around the world, has been to reduce the total amount of fat in the diet and replace with carbohydrates. However, research trials using this approach have produced only modest results at best, and despite the active promotion of low fat eating and an apparent decline in fat consumption, rates of overweight and obesity have continued to climb. More recently low glycaemic index (GI) and high protein diets have become popular and are widely used by the public. However, only a small number of randomised controlled trials have been conducted and none directly comparing the two. Both approaches effectively reduce glycaemic load (GL) and aim to reduce post-prandial glycaemia and insulinaemia. This study aimed to evaluate the ability of diets with reduced GL to enhance the weight loss effects of a reduced-fat diet, to compare the two approaches of reducing GL on metabolic and anthropometric changes, and to investigate any benefit of combining both approaches to produce the lowest GL. Methods: We conducted a 12-week intervention in 129 overweight or obese young adults who were assigned to one of four diets with varying GL, protein, carbohydrate and GI, but similar fat (30% energy), fat type and fibre content. DIET 1 (highest GL) contained 55% E as carbohydrate; DIET 2 was a low-GI version of DIET 1; DIET 3 was a high protein diet with 25% E as protein; DIET 4 (lowest GL) was a low-GI version of DIET 3. The increase in protein in DIETS 3 and 4 came primarily from lean red meat. All key foods and some pre-prepared frozen meals were provided to maximise dietary compliance. Outcome measures were body weight, body fat, lean mass, waist circumference and the following blood parameters: total cholesterol, LDL-cholesterol, HDL-cholesterol, triacylglycerols (TAG), free fatty acids, C-reactive protein, fasting insulin, fasting glucose and leptin. Insulin resistance and β-cell function were assessed using homeostatic model assessment (HOMA) and the newer computer models HOMA2-insulin sensitivity and HOMA2-β-cell function. Results: While all groups lost similar amounts of weight (4.2 to 6.2% of initial weight, p=0.09), the proportion who lost >5% of body weight varied significantly by diet: 31%, 56%, 66% and 33% in groups 1, 2, 3 and 4 respectively (p=0.011). Differences were strongest in women (76% of the total group) who showed significant differences among groups in percentage weight change (-3.7 ± 0.6%, -5.7 ± 0.6%, -6.5 ± 0.5%, -4.1 ± 0.7% respectively, p=0.005) and fat loss (-3.1 ± 0.4kg, -4.9 ± 0.6kg, -4.8 ± 0.4kg, -3.6 ± 0.7kg respectively, p=0.007). Total and LDL-cholesterol increased on DIET 3 (high protein) compared to a fall on diet 2 (high carbohydrate/low-GI, p=0.013). TAG, HDL-cholesterol and glucose homeostasis improved on all four diets, with no effect of diet composition. Goals for energy distribution were not achieved exactly: both carbohydrate groups ate less fat and the diet 2 group ate more fibre. Conclusions: Reducing GL, through either substituting low-GI foods or replacing some carbohydrate with protein, improved the efficacy of a reduced-fat diet in women and in those with high TAG. Combining both approaches to produce the lowest GL did not promote further weight or body fat loss. Although weight loss was similar in all four diets for the group as a whole, overall clinical outcomes were superior on the high carbohydrate, low-GI diet.

Pães integrais são alimentos de consumo habitual da população brasileira, porém há poucas informações a respeito da resposta glicêmica pós-prandial, O presente trabalho teve como objetivo avaliar a resposta glicêmica produzida, em indivíduos saudáveis, após o consumo de pães de fôrma rotulados como integrais. Oito pães de fôrma integrais de três categorias (clássico, light e com grãos) foram avaliados, após o consumo de porcão equivalente a 25 g de carboidratos disponíveis, através do índice glicêmico (IG) e carga glicêmica (CG). Os voluntários (n=15) compareceram ao laboratório em jejum (10 a 12 horas), pela manhã, em onze ocasiões (três dias para o consumo do pão controle e um dia para cada tipo de pão de fôrma integral). A glicemia foi determinada em jejum (t=0) e após o consumo de cada pão nos tempos: 15; 30; 45; 60; 90 e 120 minutos. A curva de resposta glicêmica, a área sob a curva (ASC) e o cálculo do IG e CG para cada um dos pães foram realizados. Considerando a glicose como referência, os pães integrais clássicos (n=2) apresentaram alto IG (71 %); os light (n=2), IG baixo (50 %) e médio (58 %) e; os com grãos (n=4), IG baixo (44 e 49 %) e médio (57 e 60 %). Os pães de fôrma light e com grãos apresentaram IG menor que os do tipo clássico (p<0,05), os quais apresentaram IG igual ao pão francês (controle). Como foi consumida a mesma quantidade de carboidratos disponíveis, a menor proporção de açúcar solúvel na categoria light parece ter sido o fator que induziu ao menor IG observado. Em relação à CG, um pão de fôrma integral light (CG=10) e outro com grãos (CG=7) foram classificados como baixa CG; os demais pães integrais (n=6) foram classificados como média CG (11 a 16). Todos os pães integrais apresentaram CG inferior a do pão controle (CG=18) (p<0,05) e entre os integrais novamente os da categoria light e com grãos foram os que apresentaram menor CG. Assim, foi observada variação na resposta glicêmica após o consumo de pães de fôrma integrais, sendo que a redução no conteúdo de açúcares solúveis, para os pães light, e a adição de grãos integrais, nos pães com grãos, favoreceram menor elevação da resposta glicêmica pós-prandial. / Whole meal breads are part of the habitual daily diet of the Brazilian population, but there is little information on the postprandial glycaemic response. The aim of this work was to evaluate the glycaemic response produced, in healthy volunteers, following the consumption of breads labeled as whole meal. Eight whole meal breads of three different categories (classic, light and grains) were evaluated, after the consumption of a portion containing approximately 25 g of available carbohydrates, using the glycaemic index (GI) and glycaemic load (GL). The subjects (n=15) attended to the laboratory after an overnight fasting (10 to 12 hours), in eleven different occasions (three days for the consumption of the control bread and a day for each whole meal bread). In every occasion, a portion of bread containing 25 g of available carbohydrate was consumed. Capillary blood samples were taken immediately before (t=0) and 15, 30, 45, 60, 90 and 120 minutes after the consumption of test breads. The glycaemic response curve, area under the curve (AUC), GI and GL for each bread were obtained. Considering glucose as reference, the classic breads (n=2) had high GI (71 %); the light (n=2), low (50 %) and medium (58 %) GI; and grains (n=4), low (44 and 49 %) and medium (57 and 60 %) GI. The light and grain breads had lower GI than the classic (p<0,05), which presented GI similar to white bread (control). As the same amount of available carbohydrates was consumed, the reduced proportion of soluble sugars in the light category breads seems to be a factor that induced the lower GI observed. In relation to the GL, one light bread (GL=10) and a grain bread (GL=7) were classified as low GL; the other whole meal breads (n=6) were classified as medium GL (11 to 16). All whole meal breads had lower GL than the control bread (GL=18) (p<0,05), and among the whole meal breads the ones in both light and grain categories presented the lower GL. Therefore, it was possible to observe variation on the glycaemic responses following the consumption of whole meal breads, the reduction in soluble sugar content, in the light breads, and the addition of whole grains, in the grain breads, favored lower elevation in the postprandial glycaemic response.

Pães integrais são alimentos de consumo habitual da população brasileira, porém há poucas informações a respeito da resposta glicêmica pós-prandial, O presente trabalho teve como objetivo avaliar a resposta glicêmica produzida, em indivíduos saudáveis, após o consumo de pães de fôrma rotulados como integrais. Oito pães de fôrma integrais de três categorias (clássico, light e com grãos) foram avaliados, após o consumo de porcão equivalente a 25 g de carboidratos disponíveis, através do índice glicêmico (IG) e carga glicêmica (CG). Os voluntários (n=15) compareceram ao laboratório em jejum (10 a 12 horas), pela manhã, em onze ocasiões (três dias para o consumo do pão controle e um dia para cada tipo de pão de fôrma integral). A glicemia foi determinada em jejum (t=0) e após o consumo de cada pão nos tempos: 15; 30; 45; 60; 90 e 120 minutos. A curva de resposta glicêmica, a área sob a curva (ASC) e o cálculo do IG e CG para cada um dos pães foram realizados. Considerando a glicose como referência, os pães integrais clássicos (n=2) apresentaram alto IG (71 %); os light (n=2), IG baixo (50 %) e médio (58 %) e; os com grãos (n=4), IG baixo (44 e 49 %) e médio (57 e 60 %). Os pães de fôrma light e com grãos apresentaram IG menor que os do tipo clássico (p<0,05), os quais apresentaram IG igual ao pão francês (controle). Como foi consumida a mesma quantidade de carboidratos disponíveis, a menor proporção de açúcar solúvel na categoria light parece ter sido o fator que induziu ao menor IG observado. Em relação à CG, um pão de fôrma integral light (CG=10) e outro com grãos (CG=7) foram classificados como baixa CG; os demais pães integrais (n=6) foram classificados como média CG (11 a 16). Todos os pães integrais apresentaram CG inferior a do pão controle (CG=18) (p<0,05) e entre os integrais novamente os da categoria light e com grãos foram os que apresentaram menor CG. Assim, foi observada variação na resposta glicêmica após o consumo de pães de fôrma integrais, sendo que a redução no conteúdo de açúcares solúveis, para os pães light, e a adição de grãos integrais, nos pães com grãos, favoreceram menor elevação da resposta glicêmica pós-prandial. / Whole meal breads are part of the habitual daily diet of the Brazilian population, but there is little information on the postprandial glycaemic response. The aim of this work was to evaluate the glycaemic response produced, in healthy volunteers, following the consumption of breads labeled as whole meal. Eight whole meal breads of three different categories (classic, light and grains) were evaluated, after the consumption of a portion containing approximately 25 g of available carbohydrates, using the glycaemic index (GI) and glycaemic load (GL). The subjects (n=15) attended to the laboratory after an overnight fasting (10 to 12 hours), in eleven different occasions (three days for the consumption of the control bread and a day for each whole meal bread). In every occasion, a portion of bread containing 25 g of available carbohydrate was consumed. Capillary blood samples were taken immediately before (t=0) and 15, 30, 45, 60, 90 and 120 minutes after the consumption of test breads. The glycaemic response curve, area under the curve (AUC), GI and GL for each bread were obtained. Considering glucose as reference, the classic breads (n=2) had high GI (71 %); the light (n=2), low (50 %) and medium (58 %) GI; and grains (n=4), low (44 and 49 %) and medium (57 and 60 %) GI. The light and grain breads had lower GI than the classic (p<0,05), which presented GI similar to white bread (control). As the same amount of available carbohydrates was consumed, the reduced proportion of soluble sugars in the light category breads seems to be a factor that induced the lower GI observed. In relation to the GL, one light bread (GL=10) and a grain bread (GL=7) were classified as low GL; the other whole meal breads (n=6) were classified as medium GL (11 to 16). All whole meal breads had lower GL than the control bread (GL=18) (p<0,05), and among the whole meal breads the ones in both light and grain categories presented the lower GL. Therefore, it was possible to observe variation on the glycaemic responses following the consumption of whole meal breads, the reduction in soluble sugar content, in the light breads, and the addition of whole grains, in the grain breads, favored lower elevation in the postprandial glycaemic response.