Thursday, August 25, 2005
Leaping Leptin and Ghrelin Growlies
Leptin is a protein that acts as a receptor. It’s created by fat tissue. The theory is that the more fat you have, the more leptin you have and that will suppress your need to eat. Hyperleptinemia—the malfunction of the mechanisms that circulate and expend leptin -- may be large factor in obesity. Leptin has links to insulin deficiency, but it also has strong ties to weight. Deficiencies in leptin cause spikes in appetite and the “starvation reflex”—the body’s physiological response to a lack of food. About 5% of obese people are considered "relatively" leptin deficient.
Those people can benefit from leptin therapy. Leptin has two roles in human physiology. During the periods of weight maintenance, when caloric intake and use are equal, leptin levels reflect total body fat mass. During periods of weight loss and weight gain, leptin acts as a sensor of energy imbalance. Like a dietary counterweight.
A small study from The Journal of Clinical Endocrinology and Metabolism suggested that even though giving people leptin does not help them lose weight, it can help them keep weight off. The study observed six people, three obese and three normal, who dieted until they lost 10 percent of their body weight. When they lost weight, their bodies tried to slow their metabolism.
"Then we gave them injections of leptin at very low doses, just enough to put back into the blood the amount that would have been produced by the fat they'd lost," Dr. Leibel said. "We were trying to trick the brain." It’s not about having a high leptin level: but having one closest to an ideal baseline.
In short term fasts of 24 hrs, leptin levels will drop 30% from basal values. It works in reverse. Massive overfeeding over a 12 hour period can increase leptin levels by 50%. Short term changes in diet can create changes in your leptin level. In addition, the circadian rhythm—your urge to work by day and sleep by night—falls in step with your leptin levels. Leptin levels were highest between midnight and early morning hours, and lowest in the afternoon. These levels are independent of your schedule and sleeping pattern. If you live your life in conflict with this rhythm, you will run in conflict with your leptin levels. Your body gives you a pass and doesn’t expect you to have a meal at 4 AM. When you’re up at odd hours, you may well eat when your body is anticipating a fast; and sleep when your body is expecting dinner.
Fat people are hungry for a good reason. When you’re obese, your leptin levels are more susceptible to large swings. Lean subjects, stay on more of an even keel. In other words, they aren’t so leptin deficient so they don’t have the same urge to compensate when food is available.
Having comparably high leptin levels—close your baseline level—while you’re fasting is important to give you the stamina to live with a reduced calorie diet and do it with fewer cravings. Where do you locate leptin? Right now, medicinal leptin therapy is in the realm of gene therapy and that gene therapy is still in the early trial stages. Those studies are yielding great results. Test mice have dropped to two-thirds of the weight of the control group. Researchers examined the rats' fat cells and discovered "profound morphological and molecular changes." The cells became crammed with mitochondria, burning oxygen and providing energy.
What if you’re not a mouse and you’re not reading this book while flying your jet car? Because leptin is a protein, it must be injected into the body and cannot be taken orally as a pill or capsule. Imagine you metabolism is a kids looking for Lego. If you give it the right number of pieces, it can build the Eiffel tower. You can encourage leptin levels by adjusting your diet.
One study asked 12 normal-weight women to accompany balanced meals with drinks sweetened with either fructose-- a form of sugar found in corn syrup, honey and fruit-- or glucose. When the women drank the fructose drink, their levels of insulin and leptin were lower than when they consumed a drink flavored with glucose, and levels of ghrelin were higher. Ghrelin is the counterpart to Leptin. If you want a high level of leptin, you want a low level of ghrelin. Ghrelin acts to stimulate appetite. In addition, drinking the fructose drink was associated with a spike in levels of blood fats, a known risk factor for cardiovascular disease. Even though the pop bottle may say, “0% fat”, your bloodstream can’t read. Past the fructose vs. glucose swap out what can stimulate leptin? Stay tuned…There are clinical trials for leptin replacement therapy: http://www.clinicaltrials.gov/ct/gui/show/NCT00085982
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tags : Leptin Ghrelin diet food obesity