Fatty Acid Desaturase Gene Locus Interactions With Diet (FADSDIET2)

Lean and overweight subjects (Body mass index: BMI >20kg/m2 <32kg/m2 ) with CC and TT genotypes of FADS1 single nucleotide polymorphism (SNP) from the METabolic Syndrome in Men (METSIM) study, in which currently >10000 men are included from the population living in Kuopio, will be recruited. Seventy subjects with CC genotype will be selected after matching with the 70 subjects with the TT genotype for age and BMI.

After a 4-week run-in period, the subjects within each genotype group will be randomly assigned into two study groups according to medians of BMI, age and fasting plasma glucose concentration: in one group the diet will be enriched with linoleic acid (LA, sunflower oil) and in the other group with alpha-linolenic acid (ALA, camelina oil). The intervention will last for 8 weeks.

The sample size calculation is based on the observed change in arachidonic acid (AA) in the cholesterol esthers fraction between CC and TT genotypes (12.14 vs. 4.20 mol%, respectively) after the diet enriched in LA from preliminary data. Considering a β=0.80 and an α=0.025 instead of only 0.05 to account for the fact that we now have two dietary interventions instead of one, 31 participants in each study group would need to be included. Assuming around 15% of dropouts in this trial, a final sample size of 35 for each group is required.

The study diet will be isocaloric following the habitual diet of the participants with a supplement of 30-50 ml (25-45 g) sunflower or camelina oil daily depending on body weight. The dose of each oil is not known to cause any side effects or adverse events and even higher doses have been safe.

Participants will record their daily oil consumption and 4-day food records will be collected at the beginning and two times during the intervention period to measure daily intake of macronutrients and specifically different fatty acids.