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Because energy expenditure, energy burning and quality of life are the same thing, anything that raises your energy expenditure makes you feel good; for instance coffee, for two hours, and then you need another one. Anything that reduces your energy expenditure, like for instance hypo thyroidism as an example, makes you feel lousy.

My former employer, ABC Radio National, ran a very interesting interview with Dr Robert Lustig, Professor of Pediatric Endocrinology at the University of California, San Francisco. In it he talks about insulin sensitivity, leptin, obesity and sugar – specifically fructose in it’s show The Health Report.

The transcript is here: www.abc.net.au/rn/healthreport/stories/2007/1969924.htm. You can listen to the actual audio from the show’s main page.

Here’s some more:

The question is why does exercise work in obesity? Because it burns calories? That’s ridiculous. Twenty minutes of jogging is one chocolate chip cookie, I mean you can’t do it. One Big Mac requires three hours of vigorous exercise to work that off, that’s not the reason that exercise is important, exercise is important for three reasons exclusive of the fact that it burns calories.

The first is it increases skeletal muscle insulin sensitivity, in other words it makes your muscle more insulin sensitive, therefore your pancreas can make less, therefore your levels can drop, therefore there’s less insulin in your blood to shunt sugar to fat. That’s probably the main reason that exercise is important and I’m totally for it.

The second reason that exercise is important is because it’s the single best treatment to get your cortisol down. Cortisol is your stress hormone, it’s the hormone that goes up when you are mega-stressed, it’s the hormone that basically causes visceral fat deposition which is the bad fat and it has been tied to the metabolic syndrome. So by getting your cortisol down you’re actually reducing the amount of fat deposited and it also reduces food intake. People think that somehow exercise increases food intake, it does not, it reduces food intake.

And then the third reason that exercise is important, which is somewhat not well known, but I’m trying to evaluate this at the present time, is that it actually helps detoxify the sugar fructose. Fructose actually is a hepato-toxin; now fructose is fruit sugar but we were never designed to take in so much fructose. Our consumption of fructose has gone from less than half a pound per year in 1970 to 56 pounds per year in 2003.

And again. Here the concept of glycemic load rushes to the defence of carrots, which find themselves recently maligned for being high GI:

…glycaemic index is half the story, the other half of the story is the fibre. Here’s the way it works — carrots, let’s talk about carrots for a minute. Carrots are very high glycaemic index, what is the definition of glycaemic index? It’s how high your blood sugar goes if you eat 50 grams of carbohydrate in that food, that’s what glycaemic index is. So if you eat 50 grams of carbohydrate in carrots your blood sugar goes up very high and so that would be a high glycaemic index food. Fructose is a low glycaemic index food because fructose does not stimulate insulin, it’s all of these calories but it doesn’t stimulate insulin. So in fact a soda has a glycaemic index of 53 which is low. So you’d say oh wait a second, carrots are bad for you and a soda is good for you? Because glycaemic index is not the whole story, in fact what you really want to talk about is a related concept called glycaemic load.

Glycaemic load is glycaemic index times the amount of food you’d actually have to eat to get the 50 grams of carbohydrate, so in carrots you’d have to eat the entire truck in order to get that. Well you can’t do that, you wouldn’t do that, so in fact carrots, even though they are high glycaemic index are actually low glycaemic load. Carrots are fine, there’s nothing wrong with carrots. On the other hand fructose, I mean a soda, there’s a lot wrong with it but you wouldn’t see it in just looking at glycaemic index.

Check it out.