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Sugar...insulin...spikes...fibre. Can someone explain this to me in words of one syllable?

(10 Posts)
nkf Sun 23-Mar-14 16:02:48

I am trying to understand the science. Sugar causes insulin spikes (why) and this is bad (why?) and fibre slows it down (how?) I've read Robert Lustig's book and I don't have the scientific knowledge to make proper sense of it. Can anyone please give a non scientist a crash course in biochemistry?

tb Sun 23-Mar-14 16:32:01

The pancreas secrete insulin in response to an increase in blood sugar ie glucose. The insulin then converts the glucose in the blood to glycogen where it is stored in the liver. It is then either used up or converted to fat for storage. This is why eating something sugary in response to low blood sugar and lead to blood sugar going even lower - rebound hypoglycaemia.

Eating fibre slows down the rate at which food is digested, I think, and this means that any glucose produced during digestion is released into the blood slowly. This avoids massive sudden peaks in blood sugar, and therefore give the body a chance to burn off the sugar as it's required without the need for insulin to create temporary storage.

The danger of repeated high sugar spikes can lead to insulin resistance, which, from memory - but could be wrong, is a condition where the body doesn't 'realise' that insulin had been produced in response to the presence of sugar and keeps pouring it into the blood. This leads to weight gain and insulin resistance is a precursor of type 2 diabetes.

BIWI Sun 23-Mar-14 16:35:45

Here's a piece I wrote for MN about low carbing that might help:

Carbohydrates are a great source of energy for your body. But the amount and type of carbohydrates typically eaten in the Western diet exceed what our body needs to convert into energy, and the excess ends up being stored as fat.

When you eat carbohydrates, your body converts them into glucose. Your pancreas releases a hormone called insulin to deal with this glucose. The insulin does three things:

1. It moves the glucose in your blood stream into your body's cells for immediate energy (think of that sudden boost you get when you eat a biscuit or a piece of chocolate).

2. It transports what is left into the liver, where excess energy is converted into glycogen, which is stored in the liver and the muscles, accessible for future energy needs.

3. Once the glycogen stores are full, what is left over is converted to fat. When you eat protein or fat, your body does not produce the same insulin response.

When you consume a lot of carbohydrates, especially carbs that are easy for your body to access, such as sugar or white bread, the levels of glucose in your blood rise rapidly. Your body has to produce a lot of insulin to deal with this and level out your blood sugar.

The more insulin you produce, the more fat you're likely to lay down, as not all of the glucose will be required for immediate energy.

nkf Sun 23-Mar-14 16:42:36

Thank you so much. I get it. So, the aim should be to eat enough carbs for your daily energy needs but not extra? Or do we need to have some fat stored in the liver?

Is it a controversial theory or is it fact? I know scientists don't think quite like that but I hope you know what I mean.

BIWI Sun 23-Mar-14 17:35:18

The biology/chemistry isn't, I don't think, in dispute. However, there is lots of controversy about whether or not this is what makes us fat hmm

As far as I know from my reading, a daily intake of around 100g of carbs should be fine for most of us, with around 30g per meal.

The trouble is, our diets are based around carbs (because this is current government 'healthy' eating advice), so most people will be eating far more than that. Which is why, I would argue, rates of obesity are going up.

Personally, as a long-term low carber, I would advocate getting your carbs from vegetables and salad, and avoiding things like bread/pasta/rice/potatoes and sugar as much as you can.

Applefallingfromthetree2 Sun 23-Mar-14 17:52:16

Really don't understand the comment from tb that eating something sugary to counteract low blood sugary can lead to the blood sugar going even lower. What is the biochemistry behind that?

nkf Sun 23-Mar-14 18:00:17

I agree that carbs are everywhere and most snacks are carbs. And snacking for many people is pretty normal.

BIWI, do you eat any carbs? If so, which ones?

Also, the people who argue that it isn't sugar that makes us fat, what do they think does? Excessive calories?

BIWI Sun 23-Mar-14 18:02:56

I eat my carbs in the form of vegetables and salad. Some carbs also come from milk (in my coffee) and yoghurt (full fat) which I sometimes have for breakfast.

I occasionally eat some processed products, like sausages (I prefer The Black Farmer ones) which have some carbs, but mainly my source is an array of vegetables (not including potatoes) and salads.

BIWI Sun 23-Mar-14 18:08:13

Oh, and people who argue it's not the sugar will say it's the calories. They are the kind of people who post that if you're overweight you should 'eat less and move more'.

caroldecker Sun 23-Mar-14 20:06:32

When to body produces insulin in response to high sugar levels in the blood, it can over-produce, thus reducing the sugar level below normal. In theory, eating pure sugar will cause a glucose spike, then an insulin spike and lower than normal levels of blood sugar, hence below the opening position, but will settle over time.

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