This is a synopsis of this part of the sugar/fat issue from FAT CHANCE by Robert Lustig, MD.

Can low-fat and low-carb diets both be right? Or both wrong?  What do the Atkins diet (protein and fat), the Ornish diet (vegetables and whole grains) and the traditional Japanese diet (carbohydrate and protein) have in common?  On the surface they seem to be diametrically opposite. But they all have one thing in common: they restrict sugar. Every successful diet in history restricts sugar.

So, what is "sugar"?  Let's dig in.

Glucose:  when glucose exists in nature it is called starch. (white rice, pasta, white bread).  It is not sweet and is mostly metabolized into energy.  Too much of it will make you gain pounds but it won't make you sick.  What you don't metabolize as energy will be pushed into fat cells by the insulin released upon consumption. (anyone for a nice brisk walk after that pasta dinner?)

Sucrose: (table sugar) is half glucose (see above) and half fructose.  It's the fructose that makes fruits sweet.  The sweetness is the molecule that is addictive - once tasted, we want more!  Sugar, despite ostensibly being a carbohydrate, is really both a fat (because that's how fructose is metabolized in the liver) and a carbohydrate (because that's how glucose is metabolized - as energy.)  Sugar can be handy if you're starving and energy depleted. An offensive linebacker after 3 hrs on the gridiron can drink all the Gatorade he wants.  But the overwhelming majority of people are neither starving nor energy depleted. 

Our current fructose consumption has increased fivefold compared to 100 years ago and has more than doubled in the last 30 years.  Health conscious people often opt for fruit juice over soda.  Wrong.  Calorie for calorie 100% orange juice is worse for you than soda because it contains 1.8 gm fructose per oz while soda contains 1.7 gm fructose per oz. The fruit itself is good for you because it also contains fiber.  Eat the orange, the apple, don't drink the juice! Drink water!

Ethanol: Studies of alcohol use show that a little bit is good for you.  Alcohol, in small amounts, raises HDL (the "good" cholesterol") and red wine has the compound resveratrol, which is thought to improve insulin sensitivity and longevity.  But the toxic effects of alcohol, just like fructose, is dose-dependent. For alcohol, we have empirical evidence that in most people, a maximum dose of 50 gm per day (about 3 glasses of wine) is the threshold for toxicity. (A hangover is a good clue of toxicity.)  This is likely the same threshold for orange juice - slightly less than a quart of OJ delivers about 50 grams.  The problem is that the current average adult fructose consumption is 51 gm/day.  That means more than half the population is over the threshold.

Next, we'll tackle why is sugar so addictive?  Why has Mother Nature set us up for this addiction? And what are the consequences of daily toxicity on the liver?

Stay tuned (while you eat your veggies).