Testosterone and Aging: Menopause and Andropause
Athlete studies aside, by the time most of us, both men and women, reach our forties, our testosterone levels are about 20 percent lower than the levels we had as robust twenty-year-olds. (No wonder we're fatter and more exhausted!) In most people, testosterone levels start to fall by about 10 percent per decade (1 percent per year) after age twenty or thirty. At the same time, our bodies start to produce more SHBG, which "traps" most of the testosterone that still remains in circulation. This is bad because SHBG effectively reduces the body's "bioavailable" levels of testosterone even further. Around age fifty, women are likely to hit menopause and experience dramatic drops in both estrogen and testosterone. While men obviously don't experience menopause, at a similar age they do experience a much larger drop in testosterone levels—a change that is referred to as andropause. During this time of life, when hormone production is falling in both men and women, as many as 30 percent of people will have testosterone levels low enough to cause noticeable symptoms. Some of the clearest signs of a testosterone imbalance are changes in attitude and mood, as well as a loss of energy and sex drive. Researchers from the Mayo Clinic have documented the fall in testosterone levels to be in the range of 35 to 50 percent by age sixty in healthy men, while researchers on aging from Saint Louis University have shown that testosterone levels fall 47 percent in men from age twenty to age eighty-nine. Dozens of studies show that maintaining testosterone levels at more "youthful" levels (that is, preventing them from dropping with age) is associated with numerous health benefits in both men and women. For example, men and women with low testosterone develop abdominal obesity (belly fat), experience a loss in sex drive (interest and ability), and become depressed (or at least moody).
Preventive-medicine specialists from the University of California at San Diego have shown that high levels of stress lead to lower testosterone levels (reduced by 17 percent) and increased rates of depression in men over age fifty. Indeed, it is well described in the scientific and medical literature that men who have low levels of testosterone are more likely to suffer from depression than men with normal testosterone levels. When testosterone levels are brought back to normal, mood also returns to normal.
If you look at testosterone on an overall scale, it is not a "more is better" story, but rather one of "maintaining optimal levels is good" and "falling levels are bad." That is, it's one of overall balance.
Testosterone and Weight Gain
For many people, perhaps the most noticeable side effect of a falling testosterone level will be an expanding waistline. Just as increasing cortisol levels can lead to excess belly fat, so can declining testosterone levels—and when you have both occurring simultaneously (cortisol rising and testosterone falling), it is virtually inevitable that weight gain will follow.
One study, published in 1996 in the Journal of Clinical Endocrinology and Metabolism, showed that obese women who boosted their testosterone levels lost significantly more abdominal fat and gained more muscle mass compared to women who were given a placebo and whose testosterone levels remained suppressed. This was ten long years ago—and still most doctors and health professionals view testosterone strictly as a "male" hormone, when the reality is that while women certainly don't want "male levels" of testosterone, they definitely want to maintain what they have.
The scientific literature in support of maintaining normal youthful testosterone levels (versus allowing them to fall in the face of stress and aging) is at least as strong as the research in support of maintaining normal youthful cortisol levels (which rise in response to stress and aging). Here is a sampling of some of the available studies:
Austrian medical researchers have shown that weight loss from dieting results in a significant reduction in testosterone levels in overweight women. But this effect is largely due to a high level of dieting stress caused by excessive calorie restriction (which elevates cortisol) and that is not unbalanced out bywith exercise (which could maintain testosterone levels). Researchers from Penn State University have shown that weight loss induced by diet alone leads to a significant drop in testosterone and fat-free mass (muscle)—an effect that can reduce metabolic rate and make weight regain easier. Scientists from Northwestern University, in Chicago, have shown that weight gain in young men (ages twenty-four to thirty-one) was significantly related to low testosterone levels, with a graded relationship between the lowest testosterone levels and the greatest degree of weight gain. In a related series of studies, researchers at Cornell Medical College, in New York, found that the age-related decrease in testosterone is significantly exacerbated in overweight men with the metabolic syndrome. As testosterone drops, body weight goes up—and the drop in testosterone and the rise in weight are more pronounced in men who have metabolic syndrome than it is in men without. (Men who don't have the condition also gain weight as testosterone drops, but to a less severe degree.)
As part of the Massachusetts Male Aging Study (which followed over seventeen hundred men, ages forty to seventy), researchers at the New England Research Institutes found that overweight men had significantly lower testosterone levels and a greater rate of decline compared to normal-weight men of any age. Endocrine researchers in Venezuela have found that testosterone levels are lower in overweight men ages twenty to sixty and that there is a graded and proportional relationship between low testosterone and weight gain (the fattest men had the lowest testosterone). Norwegian medical researchers have shown that the lowest levels of testosterone are found in men with the most pronounced central (abdominal) obesity. In addition, those with lower testosterone also had higher blood pressure and increased rates of diabetes. These findings suggest that testosterone may have a protective effect against weight gain and development of diabetes and hypertension.
In a very important study from researchers in aging at the University of Florida, the incidence of low testosterone in a general population of men over age forty-five was estimated to be 38.7 percent. Those with low testosterone were also about twice as likely to be overweight and to have hypertension, high cholesterol, and diabetes.
In a study from researchers at the Albert Einstein College of Medicine, in New York, overweight men were shown to have reduced testosterone levels, with the lowest levels seen in men who continued to gain weight over time (eight years follow-up). Interestingly, the level of testosterone was found to predict subsequent weight gain: Lower testosterone related specifically to increased weight gain in the abdominal area.
Australian scientists at the University of Adelaide have shown that testosterone levels decline with aging even in healthy men—and also lead to obesity and metabolic syndrome.
Italian hormone researchers have shown a negative relationship between C:T ratio and obesity in men and women. As stress-related cortisol levels rise, testosterone levels drop in both sexes, leading to weight gain, especially within the abdominal area.
Public-health researchers in Hong Kong have shown that age-related declines in testosterone are associated with increased levels of abdominal fat and higher rates of the metabolic syndrome. In a series of studies, low testosterone levels explained 35 percent of the variance in metabolic syndrome rates (more metabolic syndrome equated with lower testosterone).
Brazilian medical researchers have found low testosterone levels to be strongly associated with weight gain and specifically with higher abdominal fat (waist-to-hip ratio). Norwegian researchers have shown that the lowest testosterone levels are found in subjects with high waist circumference, even when their total level of body fat is rather normal, suggesting that waist circumference (abdominal fat) is the preferred anthropometric measurement to predict testosterone levels (bigger waist = lower testosterone).
Health researchers from Oklahoma State University have demonstrated a direct effect of testosterone on adipose tissues (fat cells) and obesity, showing that testosterone leads to an increase in lipolysis (fat breakdown). Normal testosterone levels lead to a normal distribution of body fat, but as testosterone levels decrease in response to stress and aging, there is a tendency to increase central obesity (gain abdominal fat). In fact, bringing testosterone levels back to within normal ranges in older men and women has been shown to reduce the degree of central obesity.
Researchers at the University of Washington, in Seattle, have shown that among women who lose weight using dietary restriction alone, each 2 percent loss of body weight is associated with a fall in testosterone levels of 10 to 12 percent. These studies represent only a fraction of the research on the relationship between testosterone, stress, cortisol, and weight gain, but it should be clear to you by now that the failure to maintain a normal C:T balance is an important reason why weight gain (and regain) is so easy for so many people. As we attempt to lose weight, our bodies try to "fight back" by slowing metabolism and conserving body fat through a rise in cortisol levels, a drop in testosterone levels, and a decline in muscle mass and metabolic rate. As a result of these metabolic changes, fat cells lose the "fat-breakdown" signal (testosterone) and receive the "fat-storage" signal (cortisol)—and weight appears (or easily comes back).