It’s well known that the hormone testosterone — the hormone which makes a man a man — declines with age, and that it’s declining also in all men over time. Low testosterone and obesity reinforce each other in a positive feedback loop, which is the low testosterone and obesity vicious cycle. Check out the chart below for the decline, both age-related and secular. A man about age 60 has a full 100-points lower testosterone in 2002-04 than in 1987-89.
The secular decline could be caused by environmental chemicals — endocrine disruptors. Just yesterday, a report was published that found that sperm quality in dogs has declined, fewer male dogs were born, and phthalates and PCBs, i.e. endocrine disruptors, were found both in the dogs and in their commercial food.1 (Another good reason not to feed your pets commercial pet food.)
What about the age-related decline in testosterone? Much of this seems to be due to decreased muscle and increased fat mass.2
Fat tissue is a potent source of the enzyme aromatase, the sole function of which is to convert testosterone to estrogens, mainly estradiol. This hormone functions in feedback inhibition of testosterone, so that more estradiol leads to lower testosterone.
As a result of less muscle and more fat, more aromatase converts testosterone to estradiol, which in turn increases fat mass even more, especially visceral fat mass.
In turn, greater visceral fat mass leads to insulin resistance, dyslipidemia, and higher risk of cardiovascular disease. Further changes then occur. Quoting from the paper:
All of these factors eventually contribute to the CHAOS Complex: coronary disease, hypertension, adult-onset diabetes mellitus, obesity and/or stroke as permanent changes unfold. Other consequences of the chronic hypogonadal state include osteopenia, extreme fatigue, depression, insomnia, loss of aggressiveness and erectile dysfunction all of which develop over variable periods of time.
Man, that’s some bad stuff — basically almost anything that can go wrong with a man in older age.
That’s the vicious cycle of low testosterone -> obesity -> more estradiol -> even lower testosterone -> low quality of life and disease.
Don’t let it happen to you.
How do you stop this vicious cycle from getting started, or if you’re in the midst of the cycle, how do you get out of it? The first two on this list are all but mandatory; if you still need help after those, consider the second two.
To know whether you have a problem to begin with, you should get tested.