The Cause of Weight Gain and Obesity

Eating or drinking the acid from fruit called fructose can induce leptin resistance, a condition that can easily lead to becoming over-acid and then overweight when combined with high animal fats, 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-caloric diet, this is the first study to show that leptin resistance can develop as a result of high acid 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.

The study, "Fructose-induced leptin resistance exacerbates weight gain in response to subsequent high-fat feeding," was carried out by Alexandra Shapiro, Wei Mu, Carlos Roncal, Kit-Yan Cheng, Richard J. Johnson and Philip J. Scarpace, all at the University of Florida College of Medicine in Gainesville. The study appears in the American Journal of Physiology - Regulatory, Integrative and Comparative Physiology, published by The American Physiological Society.

Leptin is an acidic hormone that is released when the body is trying to balance food intake with energy expenditure. When leptin isn't eliminated -- that is, when the body no longer responds to the acid leptin, it produces -- it's called leptin resistance. Leptin resistance is associated with weight gain and obesity in the face of a high acid, high-calorie diet.

Obesity or over-acidity 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. Acidic fructose is the acid sugar found in fruit. Table sugar and high-fructose corn syrup are about 50% fructose and these ingredients have become increasingly common in many foods and beverages. With the acids of sugar and high-fructose corn syrup being added to many foods, people now eat much more fructose than ever before which is making them sick, tired and over-acid or fat.

The University of Florida researchers hypothesized that a high-fructose diet could lead to leptin resistance, which in turn could lead to exacerbated weight gain in the face of a high-fat, high-calorie diet, a typical diet in industrialized countries. To test their hypothesis, the research team performed a study with two groups of rats. They fed both groups the same diet, with one important exception: one group consumed a lot of fructose while the other received no fructose.

During these six months, there were no differences in food intake, body weight, and body fat between rats on the high-fructose and the rats on the fructose-free diets. In addition, there was no difference between the two groups in the levels of leptin, glucose, cholesterol or insulin found in their blood. There was only one difference at the end of the six months: The rats on the high-fructose diet had higher levels of the acid triglycerides in their blood.

The researchers next tested the animals to see if they were leptin resistant. They injected all the animals with leptin, to see if they would respond by eating less. Animals whose leptin response is functioning normally will lower their food intake. The researchers discovered that the rats on the high acid-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."

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 animal-fat, high-calorie diet -- the kind many Americans eat. They found that the animals exposed to the high acid-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:

1) develop by eating a lot of the high acid-fructose

2) develop silently, that is, with very little indication it is happening

3) result in weight gain when paired with a high animalfat, calorie dense diet

Scarpace said the study suggests it is the interaction between consumption of large amounts of high acid-fructose-containing foods and eating a high animal-fat, high-calorie diet that produces the weight gain. "This study may explain how the global increase in fructose consumption is related to the current obesity epidemic," Shapiro said.

According to Dr. Robert O. Young, Director of Research at the pH Miracle Living Center, "fructose is an acid from fruit and is toxic to the body. The body will attempt to eliminated the fructose through urination, defecation, and/or perspiration. If the fructose is not eliminated it is taken up into the colloidal connective tissue, the extra cellular matrix and then the fatty tissues. This can lead to connective tissue disorders and weight gain. The body will always force acid (including fructose) out of the blood into the fatty tissues to protect the organs that sustain life. The body retains fat as a buffer for excess metabolic and dietary acid that is not being properly eliminated. This is the cause of weight gain and obesity."