By Mike Roussell, Ph.D. for Shape.com

Optimize your body’s secret weight-loss weapons.

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  • Ghrelin

    Ghrelin is your hunger gremlin. It is produced in your stomach and, like many fat-loss hormones, works with your brain to signal that you are hungry. Reducing calories, in an effort to lose weight, causes an increase in ghrelin. Even after 12 months of a reduced-calorie diet, research shows that ghrelin levels stay elevated. In other words, your body never adapts to eating less and constantly sends the "I'm hungry" signal, which is why maintaining weight loss is often harder than losing it in the first place. The good news: Intense exercise decreases ghrelin levels, making it a key component to fat loss and weight maintenance.

  • Leptin

    Leptin is a type of hormone called an adipokine that is released exclusively from fat cells. Leptin interacts with your brain to get your body to eat less and burn more calories. The more body fat you have, the more leptin your fat cells will release. However, too much body fat leads to too much leptin being released -- a condition called leptin resistance. When this occurs, your brain becomes numb to leptin's signal. To maximize leptin sensitivity, get adequate sleep and pack your diet full of antioxidant-rich berries and green and red vegetables. Losing weight also enhances leptin sensitivity and gives you some momentum, as the more weight you lose, the more effective leptin will become in your body. <em>Flickr photo by <a href="http://www.flickr.com/photos/notahipster/3715806806/" target="_hplink">little blue hen</a></em>

  • Adiponectin

    Adiponectin is another adipokine, but unlike leptin, the leaner your body is the more adiponectin your fat cells will release. Adiponetin enhances your muscle's ability to use carbohydrates for energy, boosts your metabolism, increase the rate in which your body breaks down fat, and curbs your appetite. You can maximize your adiponectin levels by moving more during the day (getting leaner) and replacing carbohydrates in your diet with monounsaturated fats (olives, avocados, etc). <em>Flickr photo by <a href="http://www.flickr.com/photos/bludgeoner86/2136959301/" target="_hplink">Bludgeoner86</a></em>

  • Insulin

    Insulin plays a very important role in your body and is key for recovering from exercise, muscle building, and maintaining optimal blood sugar levels. However, when carbohydrate intakes are high and insulin is left to run wild in the body, it can inhibit the breakdown and burning of stored fat. Insulin and carbohydrates are very tightly linked. The more carbohydrates you eat, the more insulin will be released. To optimize insulin for fat loss, aim to get most of your carbohydrates from vegetables and some fruit. Limit grains and starches to smaller portions directly after exercise. Flickr photo by <a href="http://www.flickr.com/photos/vinothchandar/5612099123/" target="_hplink">VinothChandar</a>

  • Glucagon

    Glucagon is a hormone that acts directly opposite to insulin. While insulin stores carbohydrates and builds fat, glucagon is responsible for breaking down stored carbohydrates and fats and releasing them so your body can use them for energy. Eating a protein-rich, low-carbohydrate meal is the best way to maximize glucagon release. <em>Flickr photo by <a href="http://www.flickr.com/photos/adactio/200944451/" target="_hplink">adactio</a></em>

  • CCK

    Short for Cholecystokinin, this hormone is released from the cells in your intestines whenever you eat protein or fat. But CCK doesn't just stay in your gut. Instead, it communicates with your nervous system to flip the satiety switch while simultaneously working with your stomach to slow the rate of digestion. The end result is that you feel fuller longer. Take full advantage of CCK by making sure you have protein and fat at every meal.

  • Epinephrine

    Known as a fight or flight hormone, epinephrine drives the burning of fat and its release for energy in the body. Epinephrine can also aid in appetite suppression. Exercise is the best way to turn on epinephrine release in your body, interval training in particular cranks up epinephrine.

  • Growth Hormone

    Considered to be the fountain of youth by many, growth hormone also helps with fat loss. Growth hormone interacts with fat cells and coaxes them to break down and burn stored fat for energy. Growth hormone can be increased through intense exercise like intervals or circuit training and sleep. To maximize the fat-burning effect of growth hormone, train hard and sleep well. <em>Flickr photo by <a href="http://www.flickr.com/photos/calliope/3029028969/" target="_hplink">Muffet</a></em>

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