How Hormones Affect Your Nutritional Needs
Hormones affect your resting energy expenditure (REE) —the amount of energy (calories) you use when your body’s at rest. Men and women need different amounts of calories and different types of nutrients in their diets to maintain optimal health.
Your pituitary gland, a small structure in the center of your brain, stimulates your thyroid gland (which sits at the front of your throat) to secrete hormones that influence the rate at which your tissues burn nutrients to produce energy.
If you’re a woman, you know that your appetite rises and falls in tune with your menstrual cycle. In fact, this fluctuation parallels what’s happening to your (REE), which goes up just before or at the time of ovulation. Your appetite is highest when menstrual bleeding starts and then falls sharply. Yes, you really are hungrier (and need more energy) just before you get your period.
Being a man (and making lots of testosterone) makes satisfying your nutritional needs on a normal American diet easier. Your male bones are naturally denser, so you’re less dependent on dietary or supplemental calcium to prevent osteoporosis (severe loss of bone tissue) late in life. You don’t lose blood through menstruation, so you need only two-thirds as much iron. Best of all, you can consume about 10 percent more calories than a woman of the same weight without adding pounds.
Teenage boys’ developing wide shoulders and biceps while teenage girls get hips is no accident. Testosterone, the male hormone, promotes the growth of muscle and bone. Estrogen gives you fatty tissue. As a result, the average male body has proportionally more muscle; the average female body, proportionally more fat.
Muscle is active tissue. It expands and contracts. It works. And when a muscle works, it uses more energy than fat (which insulates the body and provides a source of stored energy but does not move an inch on its own). What this muscle versus fat battle means is that the average man’s REE is about 10 percent higher than the average woman’s. In practical terms, that means a 140-pound man can hold his weight steady while eating about 10 percent more than a 140-pound woman who is the same age and performs the same amount of physical work.
No amount of dieting changes this unfair situation. A woman who exercises strenuously may reduce her body fat so dramatically that she no longer menstruates — an occupational hazard for some professional athletes. But she’ll still have proportionately more body fat than an adult man of the same weight. If she eats what he does, and they perform the same amount of physical work, she still requires fewer calories than he to hold her weight steady.
And here’s a really rotten possibility. Muscle weighs more than fat. This interesting fact is one that many people who take up exercise to lose weight discover by accident. One month into the barbells and step-up-step-down routine, their clothes fit better, but the scale points slightly higher because they’ve traded fat for muscle — and you know what that means: Sometimes you can’t win for losing.