Overfeeding polyunsaturated and saturated fat causes distinct effects on liver and visceral fat accumulation in humans.
Level 2 - randomized trial
Double-blind, parallel-group randomized controlled trial
PubMed 24550191 · doi:10.2337/db13-1622
What was done
In the double-blind, parallel-group LIPOGAIN randomized trial, 39 young, normal-weight individuals were overfed muffins high in saturated fatty acids (SFAs from palm oil) or n-6 polyunsaturated fatty acids (PUFAs from sunflower oil) for 7 weeks. Liver fat, visceral adipose tissue (VAT), abdominal subcutaneous adipose tissue (SAT), total adipose tissue, pancreatic fat, and lean tissue were measured using magnetic resonance imaging (MRI). Transcriptomics was performed in SAT.
What was found
Both groups gained a similar amount of weight. Overfeeding SFAs markedly increased liver fat compared with PUFAs and caused a twofold larger increase in VAT than PUFAs. Conversely, PUFAs caused a nearly threefold larger increase in lean tissue than SFAs. Changes in liver fat were positively correlated with plasma SFAs and inversely correlated with PUFAs. Distinct transcriptomic responses were observed in SAT for genes regulating energy dissipation, insulin resistance, body composition, and adipocyte differentiation. Exact numerical values and confidence intervals were not reported in the abstract.
Why it matters
These findings show that dietary fat composition during hypercaloric feeding influences tissue partitioning, demonstrating that saturated fat promotes ectopic and visceral fat accumulation while polyunsaturated fat favors lean tissue gain independent of total weight gain.
Limits
The sample size was small (n = 39) and restricted to young, normal-weight individuals, limiting generalizability to older or metabolically impaired populations. The abstract does not report baseline values, absolute fat mass changes, or numerical effect sizes. Specific oil sources (palm oil vs. sunflower oil) were used, which may not reflect all SFA or PUFA sources, and long-term clinical endpoints beyond 7 weeks were not evaluated.
Cited by
- supports Twelve-week clinical trials show that feeding a high-saturated-fat diet increases liver fat more than feeding a high-polyunsaturated-fat diet.