Shannan’s Journey

Adrenaline and noradrenaline serve to increase the metabolic rate, and are also the body’s most powerful stimulators for fat breakdown. Through adrenaline and noradrenaline, the nervous system significantly impacts the rate at which you burn calories.

This works a lot like the idle on a vehicle: the higher the idle, the more gas the vehicle uses at rest. The higher the levels of the catecholamines, the more calories you burn every day. Not only do they affect the number of calories you burn, they also affect the type of energy you burn.

Adrenaline is released in response to any stress including exercise. The greater the exercise stress, the greater the adrenaline release. Increasing adrenaline helps explain why HIT cardio tends to be more effective for fat loss than low intensity cardio. The more effort you put into exercise, the greater the subsequent adrenaline release.

Drugs like ephedrine, caffeine, and clenbuterol also mediate their fat-burning effects through increasing adrenaline and noradrenaline. It should also be noted that the same things that boost adrenaline also boost growth hormone, and they work by many of the same mechanisms.

How adrenaline breaks down fat:

Adrenaline latches onto receptors called adrenoreceptors located on fat cells and generates a metabolite called cyclic adenosine monophosphate, or CAMP. CAMP activates an enzyme called hormone-sensitive lipase (HSL). HSL then breaks down stored body fat into free fatty acids (FFAs). The FFAs then leave the fat cell and are carried by the blood to the muscles, where they are burned for energy.

You always have some adrenaline floating around in the bloodstream. The magnitude of resting adrenaline levels and your sensitivity to it is one of the biggest factors determining how easily you gain or lose fat.

With elevated blood adrenaline (or increased sensitivity), you not only have a higher metabolic rate, but also easily pull fat out of storage to be burned. With lower blood adrenaline you have to work a bit harder, which means dropping insulin, reducing calories, and taking steps to elevate blood adrenaline (more exercise).

One of the main reasons men tend to have an easier time shedding fat than women is because the lipolytic (breaking down of fat) impact of adrenaline tends to be greater in men, particularly younger men, as testosterone increases the density of adrenaline receptors in fat cells.

Insulin and adrenaline:

Recall that insulin blocks HSL from breaking down fat, and that adrenaline boosts HSL. So basically, insulin and adrenaline play a game of tug of war on the fat. The extent to which insulin interferes with fat burning depends on a few things.

If you’re eating a lot of carbs and both insulin and adrenaline are high, insulin tends to win the battle and will suppress lipolysis. Now, which one comes out ahead under real world conditions is somewhat variable and depends on circulating levels of insulin, circulating levels of adrenaline, and your individual sensitivity to them.

Increased insulin sensitivity is a predictor of weight gain. Here’s why:

• Insulin inhibits fat burning by antagonizing HSL in the fat cell.

• Having better insulin sensitivity means it takes less insulin to get into the fat cell and negate HSL: thus fat burning is shut down at lower levels of insulin/carb intake. This partially explains why it gets harder to drop those last few pounds of fat: insulin sensitivity improves with fat loss.

• Having worse insulin sensitivity means it takes more insulin to deactivate HSL. Thus, fat burning continues even with higher levels of insulin/carbs. This explains why sedentary/overweight people (who are often somewhat insulin resistant) often notice such dramatic physical changes when they begin exercising, even on less than optimal diets.

• Elevated adrenaline increases fat burning both by increasing HSL, and acutely reducing insulin sensitivity. The reduction in insulin sensitivity isn’t a diabetic type reduction, but it’s enough to make it harder on insulin to inhibit HSL and shut down fat burning. This is another reason it gets harder to drop fat as you get leaner — natural levels of adrenaline decline, resulting in an increase of the anti-fat releasing effect insulin has on HSL…..

This entry was posted on Monday, September 15th, 2008 at 6:21 pm and is filed under Training. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.