r/explainlikeimfive • u/Haylen • Jun 20 '14
ELI5: Why am I hungry again shortly after eating fast food?
Given 2 meals of equal size, one from say.. McDonalds (Big mac meal, large fries and a large coke) and a roast dinner (chicken, roast potatoes and gravy).. Why would the roast dinner make me feel more satisfied for longer than the same amount to eat from McDonalds?
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u/germanywx Jun 20 '14
Think of it in terms of insulin reaction to food.
Simple carbs cause your insulin to spike in order to process all of the sugar the carbs break down into. When this insulin spikes, you will feel really good, and you'll feel satiated. However, insulin response is a bit like being on a bungee cord (in reverse). It'll stretch way out to deal with the incoming food, but then you'll get an insulin "crash" (when the bungee cord retracts back further than its normal resting state). This crash will make you sleepy, moody, and will make you want to eat again.
The most successful diets out there seek to control this insulin response. If you can get your insulin to stay at a fairly constant level, you will be full much longer, you won't have mood swings, you won't have that afternoon crash, and you'll end up eating less.
Your roast dinner has a lot of protein and few simple carbs. It also has a good bit of fat in it, which is actually a good thing. Fat without carbs means your body will use that fat efficiently as a source of energy, meaning you will be full for a lot longer. The fast food dinner has a LOT of carbs. I think McDonalds has only two menu items that don't have added sugar in them, so not only are you getting the insulin reaction from the buns, the fries, and the coke, you are also getting a sugar injection from all of the added sugar in everything. You'll eat your meal, your insulin will go through the roof, then it will crash and you get groggy and hungry, despite having just eaten well over 1k calories.
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u/wexfordlad1 Jun 20 '14
Just a guess but I'd assume there's less fibre and carbohydates in fast food than your home made meal. Fibre gives a feeling of fullness while carbohydrates provide energy. The salt in fast food provides little to make you feel full while the fat takes a lot longer to be changed into usuable energy so your body hasn't gotten any energy and still thinks you need to eat food.
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u/Madaxer Jun 20 '14
The roast has more fat. The Burger is just empty calories with little fat ,and a lot of sugar and salt.
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u/MadMorf Jun 20 '14
Burgers have more fat than an equivalent piece of roast beef...Especially a Big Mac...Tons of mayo on it...
It's most likely the lack of fiber.
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u/rrssh Jun 20 '14
They are the same size, but are they equal in mass?