Effect of dietary fat intake and genetics on fat taste sensitivity: a co-twin randomized controlled trial

Background: Individuals with impaired fat taste (FT) sensitivity have reduced satiety responses after consuming fatty foods, leading to increased dietary fat intake. Habitual consumption of dietary fat may modulate sensitivity to FT, with high consumption decreasing sensitivity [increasing fatty acid taste threshold (FATT)] and low consumption increasing sensitivity (decreasing FATT). However, some individuals may be less susceptible to diet-mediated changes in FATT due to variations in gene expression. Objective: The objective of this study was to determine the effect of an 8-wk low-fat or high-fat diet on FATT while maintaining baseline weight (<2.0 kg variation) to assess heritability and to explore the effect of genetics on diet-mediated changes in FATT. Design: A co-twin randomized controlled trial including 44 pairs (mean ± SD age: 43.7 ± 15.4 y; 34 monozygotic, 10 dizygotic; 33 women, 10 men, 1 gender-discordant) was conducted. Twins within a pair were randomly allocated to an 8-wk low-fat (<20% of energy from fat) or high-fat (>35% of energy from fat) diet. FATT was assessed by a 3-alternate forced choice methodology and transformed to an ordinal scale (FT rank) at baseline and at 4 and 8 wk. Linear mixed models were fit to assess diet effect on FT rank and diet effect modification due to zygosity. A variance components model was fit to calculate baseline heritability. Results: There was a significant time × diet interaction for FT rank after the 8-wk trial (P < 0.001), with the same conclusions for the subset of participants maintaining baseline weight (low-fat; n = 32; high-fat: n = 35). There was no evidence of zygosity effect modification (interaction of time × diet × zygosity: P = 0.892). Heritability of baseline FT rank was 8%. Conclusions: There appears to be little to no genetic contribution on heritability of FATT or diet-mediated changes to FATT. Rather, environment, specifically dietary fat intake, is the main influencer of FT sensitivity, regardless of body weight. This trial was registered with the Australian New Zealand Clinical Trials Registry at http://www.anzctr.org.au/ as ACTRN12613000466741.