The average person is 3 stone (42lbs/20kg) heavier today than we were back in the 1960's - and the finger is strongly pointed at sugar. In brief, Ancel Keys wrongly argued that fat was the cause of obesity, and governments backed the food industry's move to towards low fat foods. But up went the sugar content because food, without fat, doesn't taste good. In the US the average person now eats 90lbs of sugar a year, hidden in just about any foods, but the biggest increase came from fizzy drinks, and also confectionary.
In Britain, from the 80's we all started snacking on sweets. Sugar, originally derived from cane, was replaced by high fructose corn syrup, which was cheaper. It's also sweeter and turns more readily into fat. You also eat more because it suppresses the action of leptin, a hormone that stops you eating. We got fatter and more used to sweet foods which literally become addictive. Sugar and blood sugar problems also makes your memory decline faster. A study out today in the Archives of Neurology finds that well-functioning older adults with diabetes "have reduced cognitive function and that poor glycemic control may contribute to this association,” the authors conclude. Researchers at Columbia University in New York have found that twice as many people with high insulin levels, the consequence of eating too many sweet foods, develop dementia when compared to those with normal insulin (J. A. Luchsinger, et al., Neurology, 2004)
Also, the people with high insulin levels had the greatest decline in memory.(W. L. Xu, et al., Neurology, 2004) An Italian study of people free from dementia and diabetes showed that high insulin levels are strongly associated with poorer mental function. (A. M. Abbatecola, et al. Journal of American Geriatric Society, 2004) Insulin levels go up the more 'insulin resistant' or insensitive yo become. Blood sugar levels then rise more than they should because insulin takes longer to kick in. As a result you get more sugar -coated red blood cells, called glycosylated haemoglobin. This is also one of the most important hallmarks of 'metabolic syndrome' which I call internal global warming because it mreans your metabolism has shifted into an unhealthy state that piles on the pounds.
Researchers at the University of California, San Francisco, studied 1,983 postmenopausal women and found those with glycosylated haemoglobin levels of 7 per cent or higher were four times more likely to develop mild cognitive impairment or dementia. (Yaffe, K, et al., Archives of Neurology, 2009). Having a healthier diet in mid-life means less risk for memory loss down the track. (W.Kesse-Guyot, Journal of Nutrition, 2012). Also, a high sugar intake in childhood predicts convictions for violence in adulthood (age 34 years). (S. Moore, British Journal of Psychiatry, 2009). Many studies have shown that the higher a young person's sugar intake the more violent, disruptive is their behaviour and concentration and attention span worsens.
Sugar, and losing blood sugar control, is also linked to worsening mood.Non-depressed people with metabolic syndrome at baseline are twice as likely to have depressive symptoms at 7 year follow-up(Koponen H et al. J Clin Psychiatry, 2008). Also, metabolic syndrome in childhood, in turn, predicted higher levels of depressive symptoms in adulthood (Pulki-Rabak L et al, Health Psychology, 2009). Fructose, while having a lower GI than sucrose (which is one unit of glucose and one of fructose), seems to be worse than pure glucose because the body doesn't get the immediate signal that you've had enough sweet. Nature only ever supplies fructose with copious amounts of fibre, effectively slow-releasing it.
That's why I say eat your fruit, don't drink it. Berries, cherries and plums have the least fructose, with their main sugar being xylitol, which doesn't effect your blood sugar. The trick to losing weight, and staying sharp is to eat a low GL diet, which I explain in my Low Gl Diet Bible. I recommend you watch the second and third part of this BBC documentary, being shown at 9pm on Thursday on BBC2.