You: On a Diet plus Collins GEM Calorie Counter Set. Michael Roizen F.

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      Of course, the place to start is with your metabolism, your body’s thermostat—the rate at which you burn off extra fat (metabolism literally means “change”).

      FACTOID

      One theory about metabolism says that cold temperature stimulates appetite. (Ever notice you eat more during the winter, and you’re not hungry after exercising, when your body’s warm?) And people with low body temperature have lower metabolism and will be prone to gaining weight.

      Most of the 1 million calories you consume every year are burned without your ever thinking anything of it. It takes energy for you to breathe and sleep, and for all of your organs to function. The energy you consume and store is used primarily to power your anatomical systems and structures. YOU-reka! Only 15 percent to 30 percent of your calories are burned through intentional physical activity such as exercise, walking, or doing the wumba wumba on your anniversary. So while you may think that spinning class or Bikram yoga is the primary pathway to frying fat, physical activity is only a fraction of it. You burn most of your calories by keeping your heart pumping, your brain remembering your spouse’s birthday, and your liver disposing of last night’s vodka concoction.

      Now, that doesn’t mean there aren’t many outside influences that slow down and speed up your burn rate. Any movement speeds metabolism, including fidgeting (called nonexercise activity thermogenesis in scientific lingo, or NEAT for short). Every increase in body temperature of one degree increases your metabolic rate by 14 percent (eating protein appears to do the same thing naturally, by the way). When you sleep, your metabolic rate decreases by 10 percent. YOU-reka! When you starve yourself for more than twelve hours, your metabolic rate actually goes down by 40 percent. When you skip meals, your body senses a dietary disaster and quickly goes into storage mode rather than burning mode. That’s the primary reason why deprivation diets don’t work. Your body panics about going into a famine, so it slows metabolism into emergency-storing mode rather than a steady state of burning. Breakfast eaters are on average thinner than those who skip breakfast because they keep their metabolism genes turned on; this means that calories are more likely to be burned off before they can turn into fat.

      In our battle to reduce our waistlines, we have several fearsome adversaries. And some of the greatest foes we will meet on the battlefield are our hormones.

      Sure, we all know that raging hormones can make a teenage boy become sex obsessed or give a menopausal woman hot flashes so bad she feels as though she’s in Death Valley in August. But you may not know that your hormones have a lot to do with whether or not you’re going to look good in a Speedo.

      Is Something Secretly Making You Fat?

      Before you hit yourself over the head with a stick of salami for lacking the willpower to resist aforementioned salami, or if you can’t figure out why you eat less than all your friends but still gain weight, consider that your hormones may be influencing your body more than you think. Glands, which make up your endocrine system and produce your hormones, are responsible for the genetic conditions that could be influencing your metabolism and your weight. The primary metabolic glands are:

      Thyroid gland: Thyroid hormone influences how quickly or slowly you burn energy. Too much hormone forces the body to waste energy too quickly (in extreme cases, it actually causes your heart muscle to become hypermetabolic and weaken). But if you don’t produce enough, you develop a condition called hypothyroidism, in which your metabolic rate turtles way down. The best way to check levels of thyroid hormone? A simple blood test. You have elevated thyroid-stimulating hormone (TSH) if it’s above 5 IU/liter. This means your body is desperately trying to build up your body’s circulating free thyroid hormone levels but is failing. TSH is released from your pituitary gland and tells your thyroid to produce two hormones that help control metabolism. Though decreased thyroid levels are rarely the sole cause of being overweight, abnormal levels may indicate that you should see your doctor or an endocrinologist about whether you need to supplement your thyroid function in the form of a thyroid pill to boost your metabolism. (Symptoms of hyperthyroidism include anxiety, heart palpitations, sleeplessness, and fast-growing hair and nails. For hypothyroidism, you may be lethargic, gain weight, have a reduced appetite, or have brittle nails.)

      Adrenal glands: Adrenal glands sit like a dunce’s cap on the kidneys, but they are controlled by corticotrophin-releasing hormone (CRH), which is made by the hypothalamus. This valuable relationship enables the adrenal to be very responsive to sensory input from the world around us, like a charging woolly mammoth. When chronically stressed, your adrenal glands produce cortisol, and cortisol inhibits CRH—which is too bad, because CRH will decrease your desire to eat. High cortisol levels reduce insulin sensitivity, so diabetes becomes more common and adversely influences fat and protein metabolism. The kidney responds to high cortisol levels by retaining salt and water so that blood pressure increases. At the same time, other hormones created by the adrenal gland, including testosterone and its derivative estrogen, increase; this can lead to obesity-linked diseases like uterine fibroids and breast cancer. To measure cortisol levels, you need a blood test or a twenty-four-hour urine collection. Above 100 milligrams in twenty-four hours generally indicates a high level of cortisol. (Note: In some people, the cutoff number varies, depending on the lab.) By the way, this is also the reason why people on steroidal medications (for asthma, for instance) seem to gain weight; cortisol is a form of steroids. (These are not the same steroids that some athletes are abusing. Those anabolic steroids are related to testosterone.)

      Figure 6.1 Gland Inquisition Too much stress overstimulates the adrenal gland, which releases too much cortisol (the stress hormone), testosterone, and estrogen. This witch’s brew encourages us to eat more and rapidly stores those calories in your belly fat.

      FACTOID

      The average woman gains twenty-four pounds between the ages of twenty-five and sixty-five. Considering that the total food intake of women over forty is more than forty thousand pounds of food, the difference between food intake and food expenditure that produces such a weight gain is .06 percent-or just 8 calories a day. And if you want to lose weight, the whole fight comes down to measly 100 calories a day-that’s ten permanent pounds and roughly three inches off your waist every year.