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Leptin |
Leptin is a protein-hormone that regulates appetite and metabolism in humans and other mammals. Leptin acts on a very small region of the brain called the hypothalamus shown here: |
Leptin was discovered by researchers studing strains of massively obese mice in 1994. It was found that some strains of these mice lacked the ability to produce leptin while others produced normal amounts of leptin but lacked the receptor protein needed in the hypothalamus to recognize leptin. When the mice who had normal receptors but couldn't produce leptin were injected with the protein, they rapidly lost very large amounts of weight. This immediately suggested that the protein could play a role in treating human obesity and several clinical trials have been undertaken since then. |
Unfortunately, leptin has not proved as effective in most people. In a very small number of individuals who, like the mice described above, lack the ability to produce leptin, the drug has dramatic effects, but in most people it is either totally innefective or produces only slight weight loss. Still, the discovery of leptin was a major breakthrough in the understanding of obesity. Leptin Resistance Leptin appears to fail in many people because they are resistant to it. In fact, many obese people have much higher levels of leptin in blood than thin people. This is true because generally, leptin is produced by fat cells and in proportion to their number and size. Administering extra leptin to people who are resistant to it doesn't help. Fructose & Leptin Resistance Research in 2008 showed that the sugar fructose (described at length here) can, when consumed in large amounts by laboratory rats, cause the animals to develop resistance to leptin in as little time as six months and worse, silently--without causing the rats to gain weight--UNTIL the rats begin eating a high fat diet at which point the former fructose eaters became significantly more obese than their counterparts who were not fed fructose in the first place. This suggests again that the sugar may be a prime culprit in weight gain in humans. |
Journal Reference: 1.Shapiro et al. Fructose-Induced Leptin Resistance Exacerbates Weight Gain in Response to Subsequent High Fat Feeding. AJP Regulatory Integrative and Comparative Physiology, October, 2008; DOI: 10.1152/ajpregu.00195.2008 |
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