Effects of Standardized Meals With Different Compositions of Fat, Protein and Carbohydrate on the Metabolic, Hormonal and Inflammatory Responses in Human

Food is an important part of human beings life. During most part of human beings history the shortage of food has been a problem. Today the shortage of food is unknown phenomena in the industrial countries. Instead human being is facing a challenge in obesity epidemic. The number of obese persons has increased since 1980 in all industrial countries. Today only 20 - 25 % of the population in the US has a normal body mass index (BMI). The populations in Europe and Asia are following the same trend. It is known that increased waist (in women > 80 cm and in men > 94 cm) are correlated to insulin resistance, especially in liver because of increased hepatic fat storage. Increased prevalence of obese persons is followed by increased prevalence of patients with impaired glucose tolerance with increased risk for diabetes type 2, cardiovascular disease and cancer.

It is known that impaired glucose tolerance and diabetes type 2 can be prevented efficiently with weight loss, reduced total intake of fat and carbohydrate, increased intake of fiber and physical activity. Three popular diets, 1) low fat, 2) low carbohydrate (high-protein and high-fat) and 3) low glycemic load, have recently received much attention. Long term studies of these different diets have shown inconsistent results. There is a discussion today if a better metabolic control is achieved with low-carbohydrate diet compared to low-fat diet in patients with diabetes type 2 compared to the diet recommended by Swedish National Food Administration. In regards of dietary composition, hyperglycemia and dyslipidemia is determined by the amount and quality of ingested carbohydrates and dietary fats. It has been suggested that postprandial hyperglycemia and hypertriglyceridemia triggers oxidative stress and causes inflammation, metabolic alterations associated with endothelial dysfunction.

An important aspect of satisfaction after a meal is the feeling of satiety. Subjective feelings of hunger are also obviously related to initiation of food behaviors such as intake of snacks. Neophobia, the fear of new or unfamiliar foods, can also be related to the success or failure of food related behavior change. These feelings of satiety are in turn related to factors such as blood glucose levels. Thus the effect of ingested macronutrients on the postprandial glycemic response is one potential mechanism by which foods may affect satiety. Compared to fats and proteins, dietary carbohydrates may have the greatest effect on postprandial glycemia and insulinemia, and may therefore elicit greater appetitive ratings several hours after consumption compared to lower-glycemic meals. Lately some neuroendocrine hormones (ghrelin, resistin etc) and adipokines (leptin and adiponectin) have received attention as regulators of satiety and plausible causes of obesity. The effect of high-fat, high-protein or low-carbohydrate meals on these hormones are not known.

The adverse effects of factors such as chronic stress and depression on general health have been documented for many decades. Apart from having an influence on specific health behaviors, other interacting influences such as general life stress appear to be related directly to alterations in pro-inflammatory and hemostasis processes. The physiological pathways by which psychosocial factors might exert both positive and negative effects on health are numerous and incompletely understood. However, examples of particular interest are findings that suggest that even in relatively healthy persons, chronic negative appraisals of minor life events (hassles) are associated with increased circulating levels of inflammatory factors, whereas persistent positive appraisals of minor life events (uplifts) are associated with decreased levels of such factors. It is thus important to consider general Quality of Life, as well as food-related quality of life together with health and taste attitudes and nutritional knowledge.

Finally the gender aspect is also of importance. Previously it has been presumed that the inflammatory and hormonal responses to different diets are the same in men and women. There are known biological and hormonal differences between men and women. One may question why women get heart infarction later in life compared to men and if the risk factors including inflammatory responses, cholesterol levels and other hormonal changes after different diets are the same in men and women.