Part 2: How sugar makes us fat (and sick) - the double whammy

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I posted yesterday on the sweet little fact that I've quit sugar, and told you that sugar makes us fat and sick. Today I want to delve a little further into how sugar does this. I highly recommend watching this talk by Robert Lustig, who is the leading expert in childhood obesity at the University of California. Lustig is one of the leading proponents in this battle against our prolific sugar consumption, and whilst his lecture does go into a little bit of 'scientificy' stuff, it manages to stay engaging and fascinating and enlightening all the way through (all 90 minutes of it - watch it in short bursts!). For a reeeally in-depth insight, read David Gillespie's Sweet Poison, Why sugar makes us fat.

The gist of Lustig's teachings, and Gillespie's writings, and results from an increasing number of research projects, is this - sugar makes us fat in two major ways. Firstly, the fructose in sugar gets converted into fat in our liver, which leads to a whole range of problems not to mention weight gain, and secondly, it changes the way our brain recognises energy, and makes us think we're starving when we're not. Explained: 

1. Fructose converts into fat. Quickly. As I said last post, our liver is the only organ in our body that can process fructose, so 100% of any fructose we eat ends up there. Once in the liver, fructose triggers a very complex metabolic process that produces 1. fat droplets (which stay in the liver, causing insulin resistance), 2. a damaging form of cholesterol called VLDL (which can cause heart disease), and 3. triglycerides, which get stored as fat in our muscle (particularly around the belly). In other words, when you eat fructose, you're eating fat. But not all of the fructose is converted into fat. Some of it ends up as uric acid, a waste product known to cause gout and high blood pressure. 

2. Fructose throws our hunger hormones out of whack. This is the second blow, the second major way fructose makes us fat - fructose, unlike glucose, does not supress the hormone in our body that tells us we're hungry (called ghrelin). So we keep thinking we are. And you know what else? It also interferes with our brain's ability to recognise leptin, the hormone that tells us we're full! In other words, we can keep eating fructose and our brain won't get the signal that we've had enough. It makes us think we're starving when we're not.

And this:

Fructose does stimulate our pleasure hormones, so on top of losing our ability to tell we've had enough of it, we want more!

Bad combo, don't you think?

More soon, stay tuned.


  1. Isn't fructose the sugar from fruit!
    What about sucrose?
    Do sucrose, lactose, and fructose all have this effect?

  2. Fructose is the sugar in fruit, but when eaten within fruit it's absorbed more slowly due to the fruit's fibre content, and this helps the liver cope with it. Even so, experts recommend only up to 2 pieces of fruit a day. It's really the highly refined fructose that's the problem. Sucrose is table sugar, which is 50:50 glucose and fructose. Lactose doesn't have this effect. Fructose isn't bad in itself when it's delivered via fruit, it's eating it refined and in the quantities we do that's the problem!



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