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How long does it take for weight to go on?

Hi, I was wondering how long it takes for food to work its way through the digestive system and turn itself to fat? I weigh more in the morning following a day when I've eaten things I shouldn't have, but understand this may be because of salt/carb content etc which results in water retention. How long does it take to actually digest food, and the "unused" calories turning to fat? Thanks!


Our expert says...


Thanks for your query!

Most of the absorption of calories and nutrients is done within 6-8 hours, as this is how long it takes for food to pass through the stomach and small intestine where major absorption occurs.

Total digestion time, including travel through the large intestine where some final processing and a lot of water absorption occurs, is usually between 24 and 72 hours. But theoretically, calories are available for laying down fat within hours, not days.

However what’s very relevant is that it takes a SURPLUS of about 3500 calories to put on a pound of fat. In other words, ifyou overeat by 1,000 calories one day and wake up 3 pounds heavier the next, you didn’t gain three pounds of fat overnight (the most you could have gained would be around a third of a pound of fat).

As you rightly point out, other factors that affect your weight include the weight of the food and liquid you just ate, the last time you went to the toilet, water retention, hormonal changes, and more.

Hope this helps!

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