Thread by @martinsipx

Dietary PUFA are oxidized preferentially in postprandial period.

"Polyunsaturated:saturated ratio of diet fat influences energy substrate utilization in the human"

pubmed.ncbi.nlm.nih.gov/3123874

#lcl6

1/9

Diet of 45-40-15%en fat-carbs-protein for 7 days + crossover of two PUFA:SFA ratios (P:S):
- low P:S = 0.24, PUFA 5%en
- high P:S = 1.65, PUFA 17%en

2/9

Higher carb vs. fat utilization on higher PUFA diet:

"These differences indicate a shift toward greater carbohydrate and lower fat utilization following an overnight fast in
subjects on the high compared to the low P:S ratio diet."

3/9

Cumulative thermogenic effect of food (TEF):
- low P:S ➡️ fat utilization rises little, TEF comes mostly from carbs
- high P:S ➡️ fat utilization rises ~50%, TEF contribution from fat and carbs is roughly similar

4/9

"In human fed 13C labeled fatty acids mixed with breakfast meal, nine-hour cumulative CO2 in breath from absorbed LA (10.2%) was greater than from absorbed SA (2.9%)[8]. After 24 hours, while CO2 production from LA was no longer measurable, that from SA was 0.5%/h."

5/9

"These findings indicate that PUFA are more rapidly diverted to use as energy substrates after consumption than are SFA; yet, following an overnight fast, their oxidation rate diminishes to a level below that of SFA."

6/9

"In addition, PUFA are diverted into pathways of ketone body production more readily than are SFA in rat liver [26]. Finally, in rat liver slices incubated with LA and PA at identical levels, LA was preferentially β-oxidized whereas PA was diverted to TAG synthesis. [27]"

7/9

"Of interest, however, is that similar trends in postprandial fat and carbohydrate oxidation on each diet were observed on day 1 and day 7, suggesting that fat type exerts an acute effect on energy substrate metabolism."

8/9

"As turnover rates of adipose lipids are in the order of several months [28], the data suggest that a change in fasting RQ, concurrent with altered postprandial substrate utilization pattern associated with TEF, is not due to large alterations in total body FA composition."

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