Stress hormones: Cortisol and epinephrine
Whether you’re fending off an angry rottweiler or an angry client, your body’s response to stress is the same: Your hypothalamus floods your blood with hormones to frighten you into action. “Cortisol and epinephrine are your body’s alarm-system hormones,” says Dr. Fonseca. They make your heart beat faster and dilate your bronchial tubes so they can feed oxygen to your brain and keep you alert. They also release fat and glucose into your bloodstream to provide emergency energy.
Are your hormones in tune? Too much stress can keep your cortisol levels consistently elevated, which disrupts your metabolic system. This, in turn, signals your cells to store as much fat as possible. Worse, the fat tends to accumulate in your belly as visceral fat, which resides behind your abdominal muscles and has more cortisol receptors than other fat does.
To defend yourself against stress-hormone disruption, make a habit of exercising for an hour a day, 3 days a week. Doing so helps regulate your cortisol levels, say researchers at Ohio State University. Also try to eat organic foods as much as possible in order to steer clear of the common pesticide atrazine. This chemical has been shown to affect hormonal balances in amphibians, reptiles, birds, and mammals. A National Health and Environmental Effects Research Laboratory study showed that atrazine produced extreme increases in stress-hormone levels in rats. In fact, the stress reaction was similar to that seen when the animals were restrained against their will, the study noted. (For more on pesticide dangers, see “Your Lethal Lawn” in this issue.)
Weight hormones: Leptin, ghrelin, CCK, insulin
You have an army of hormones telling you when to eat and when to put the fork down. The hormone ghrelin begins the cycle when your stomach is empty by prompting neurons in your hypothalamus to make you feel hungry. Then when you start eating, your stomach stretches and you secrete cholecystokinin (CCK), an appetite suppressant.
Hormones now begin working overtime to help you back away from the table. Your intestines produce peptide YY, which tells your brain you’ve had enough to eat, and your pancreas sends out insulin. This signals that you’re metabolizing a meal and that you shouldn’t consume any more. Leptin, a hormone produced by fat cells, also tells your hypothalamus that you’re full by prompting the secretion of alpha-MSH, which is another appetite-suppressing hormone.
All this helps your body maintain a balance between hunger and satiation. Why so many hormones in the game? “Energy regulation is necessary for survival, so we have many redundant pathways in case any fail,” says Robert Lustig, M.D., an endocrinologist at the University of California at San Francisco. “But we were never supposed to have so much food so readily available, and certainly not this much sugar.”
Are your hormones in tune? Hungry? Full? You may not be able to trust your gut. When you put on extra weight, you start secreting excess leptin. “And if you secrete a lot of leptin on a chronic basis, it should tell your brain, ‘Look, you’re putting on weight; you need to cut back,'” says Dr. Fonseca. But disruptions in leptin (mostly from too much sugar) instead tell your brain to send out hunger signals, even if you’ve just eaten. This can lead to fatty liver disease and insulin resistance. “When your insulin goes up, it blocks leptin signaling, which means your brain thinks you’re starving,” Dr. Lustig says. This, of course, sets up a wicked feedback cycle as you pack on the pounds.
Beyond losing weight, your best defense against leptin disruption is to reduce your sugar intake. Americans consume an average of 22 teaspoons of sugar a day; the American Heart Association recommends that men eat no more than 9. And it’s not just high-fructose corn syrup that you need to avoid; table sugar and fruit juice can be as bad as soda. In fact, 100 percent fruit juice has 1.8 grams of fructose per ounce, while soda has 1.7 grams per ounce, Dr. Lustig notes.