The Effect of Dietary Fat Modification on Risk Factors Associated With the Metabolic Syndrome

521 free-living subjects with the metabolic syndrome received one of four dietary treatments for 12 weeks: (1) High-fat (38% energy) SFA-rich diet; (2) High-fat (38% energy), MUFA-rich diet; (3) Isocaloric low-fat (28% energy), high-complex carbohydrate diet and (4) Isocaloric low-fat (28% energy), high-complex carbohydrate diet, with 1 g/d LC n-3 PUFA. A 3-day weighed food intake assessed dietary compliance pre-, mid- and post- intervention. An IVGTT, lipoprotein analysis, cytokine, adhesion molecule, coagulation factor and isoprostane levels were determined pre- and post-intervention. DNA, adipose and skeletal muscle biopsies, and PBMC were isolated to characterise nutrient sensitive molecular markers of insulin sensitivity.

Inclusion criteria

• Gender: males and females (not pregnant or lactating).
• Body Mass Index (BMI) 20-40 kg/m2
• Total cholesterol concentration equal to or < 8.0 mmol/l.
• Medications / nutritional supplements allowed, on condition that the subjects adhere to the same regimen during the intervention: anti-hypertensive medication (including beta-blockers), oral contraceptives, hormone replacement therapy, multi-vitamin supplements, other non-fatty acid based nutritional supplements (e.g. garlic, anti-oxidants, etc).
• Smokers and non-smokers.
• Regular consumers of alcohol, which is not excessive as defined by elevated liver enzymes (AST and ALT).
• Ethnicity: Intention to include white Europeans.

Exclusion criteria

• Diabetes or other endocrine disorders.
• Chronic inflammatory conditions.
• Kidney or liver dysfunction.
• Iron deficiency anaemia (haemoglobin < 12g/dl men, < 11g/dl women)
• Prescribed hypolipidaemic medication
• Prescribed anti-inflammatory medication
• Fatty acid supplements including fish oils, evening primrose oil, etc.
• Consumers of high doses of antioxidant vitamins (A, C, E, beta-carotene).
• Red rice yeast (Monascus purpureus) supplement usage.
• High consumers of oily fish (> 2 serving of oily fish per week of herring, mackerel, kippers, pilchards, sardines, salmon, trout, tuna (fresh), crabmeat or marlin). One portion is defined as a small herring or mackerel, one can of salmon or sardines or one salmon or tuna steak. Tinned tuna is permitted as it contains only minor amounts of long chain n-3 PUFAs.
• Highly trained or endurance athletes or those who participate in more than 3 periods of intense exercise per week.
• Volunteers planning to start a special diet or loose weight (e.g. the Slimfast Plan, Atkins Diet etc).
• Weight change equal or >3kg within the last 3 months.
• Alcohol or drug abuse (based on clinical judgement).
• Pregnant / lactating females / women planning a pregnancy in the next 12 months. Women who become pregnant during the dietary intervention period should be removed from the study.