Training & Nutrition - How long does it take...

to metabolise fat?

What I mean is, if I eat a Christmas Dinner with all the trimmings, how long does it take for all that fat to actually show on my waist - will it be there the next morning, or does it take longer?

Just wondering.

Immediately!

Fat pretty much piles on at a 99% rate without much digestion or metabolizing needed. Carbs & protein consume a large portion of their calories, about 50%, in getting converted to fats. Also fats are higher-calorie and physical density than carbs & protein. An equal volume & weight of fats will end up adding more weight to your torso compared to eating the same amount of carbs & protein. So if you eat extra calories, it's a lot easier to pile on weight by eating fats than carbs & proteins.

Let's take the case of an extra plate of fettucini-alfredo/carbonara or nachos:

400gm fat from cheese sauce = 3600 calories = 3564 calories fat on body = 1.0 lb fat added
200gm protein from meats = 800 calories = 400 calories fat on body = 0.11 lb fat added
300gm carbs from pasta/chips = 1200 calories = 600 calories fat on body = 0.17 lb fat added

Thanks for that. Great explaination.

400gm fat from cheese sauce = 1.0 lb fat added

400gm fat = 454gm fat added.
Miracles do happen, indeed.

400gm fat = 454gm fat added.
Miracles do happen, indeed.

DannoXYZ -- Sorry, CTA is correct on this. Your calculations are wrong. You cannot create any form of energy/mass out of nothing.

1lb = 454g. 400g of fat intake will not yield >=0.88lbs of weight gain.

Yes correct, sorry I was off. A nutritional "pound" is 3500-calories of fat due to some conversion efficiencies in getting energy out of it. While a weight "pound" is 454-grams. So even though a full pound of fat may have 4086 calories, you only have to burn off 3500-calories to lose a pound of blubber. :)