The theory that dietary saturated fat and cholesterol are associated with detrimental changes to plasma lipid levels was popularised by Ancel Keys in the 1950’s and 1960’s, and has since pervaded the scientific literature. However, recent advances in nutrition (such as the identification of further lipoprotein categories, advances in antioxidant biochemistry and separation of trans fats, hydrogenated and deodorised oils from saturated fats to their own categories) have produced evidence that has refuted many of the early claims regarding detrimental health effects of dietary lipids. In recent years, evidence has accumulated to show that high intakes of fructose, high fructose corn syrup, sucrose, and refined grains are implicated in the development of the metabolic syndrome. This disorder is characterised by insulin resistance, abdominal weight gain and detrimental plasma lipid changes, produces a systemic metabolic dysfunction which significantly increases the risk of developing cardiovascular.
The association between adiposity and adverse blood lipid changes has been demonstrated in research1 involving 7821 subjects aged 8 to 19 years, the data being taken from the National Health and Nutritional Examination Survey. Subjects had their body fat measured with dual-energy X-ray absorptiometry and high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, total cholesterol, and triglycerides (very-low density lipoprotein; VLDL), were measured in plasma. The prevalence of adverse total cholesterol (>200mg/mL), HDL cholesterol (<35mg/nL), LDL cholesterol >130mg/mL) and triglycerides (>150mg/mL) was significantly greater in subjects with high adiposity compared to those with low adiposity. Using multiple linear regression, that was adjusted for age, survey period and race, the authors concluded that the variance in lipid concentration experienced by subjects was explained 2 to 20% of the time by the adiposity level of the subject.
These results suggest that detrimental changes to plasma lipid are significantly associated with adiposity in young individuals. In particular, there was a stronger association between adiposity and adverse lipid concentrations in male subjects. This is supportive of other data in both children, adolescents and adults that suggests that adiposity is associated with metabolic dysfunction that includes detrimental changes to plasma lipid levels. In this study, body fat explained only between 2 to 20% of the variation in lipids between subjects. Other studies have looked at factors affecting blood lipid changes and research has repeatedly identified low quality diet, high in refined sugar and low in fibre, minerals and vitamins as a possible cause of lipid changes. Because low quality diets are associated with abdominal weight gain through insulin resistance, this may explain the association between adiposity and plasma lipid changes seen in this study.
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