Fructose Sets Table For Weight Gain Without Warning:
"Eating too much fructose can induce leptin resistance, a condition that can easily lead to becoming overweight when combined with a high-fat, high-calorie diet, according to a new study with rats.
Although previous studies have shown that being leptin resistant can lead to rapid weight gain on a high-fat, high-calorie diet, this is the first study to show that leptin resistance can develop as a result of high fructose consumption. The study also showed for the first time that leptin resistance can develop silently, that is, with little indication that it is happening.
Leptin is a hormone that plays a role in helping the body to balance food intake with energy expenditure. When leptin isn’t working -- that is, when the body no longer responds to the leptin it produces -- it’s called leptin resistance. Leptin resistance is associated with weight gain and obesity in the face of a high-fat, high-calorie diet.
Obesity has been a growing problem in the U.S. and in other parts of the world and fructose has been suspected of playing a role. Fructose is the sugar found in fruit, but it’s not the normal consumption of fruit that is the problem. Table sugar and high-fructose corn syrup are about 50% fructose and these ingredients have become increasingly common in many foods and beverages. With sugar and high-fructose corn syrup being added to many foods, people now eat much more fructose than ever before.
There was only one difference at the end of the six months: The rats on the high-fructose diet had higher levels of triglycerides in their blood.
The researchers discovered that the rats on the high-fructose diet were leptin resistant, that is, they did not lower their food intake when given leptin. The no-fructose animals responded normally to leptin by eating less.
This first six months of the study showed that leptin resistance can develop silently. “Usually, leptin resistance is associated with obesity, but in this case, leptin resistance developed without obesity,” Shapiro said. “This was very surprising.”
Role of diet
Having seen that leptin resistance could develop silently, the researchers next wanted to find out what would happen if they switched the rats to a high-fat, high-calorie diet -- the kind many Americans eat. They found that the animals exposed to the high-fructose diet, the leptin resistant rats, ate more and gained much more weight and fat than the leptin responsive animals on the fructose-free diet. All told, this study showed that leptin resistance can:
* develop by eating a lot of fructose
* develop silently, that is, with very little indication it is happening
* result in weight gain when paired with a high fat, calorie dense diet