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Don’t be discouraged by that groan you make when you get out of bed. But to work in your favor, you need to know what you’re up against.
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When you hit your 30s, your body starts to self-sabotage: testosterone, progesterone, and human growth hormone (HCH) begin their slow decline, causing a reduction in muscle mass that causes your metabolism to slow down.
By the time you reach 40, testosterone levels are deteriorating at a rate of 1% each year, making muscle gain more difficult. Meanwhile, an enzyme in your fat tissue converts persistent testosterone to estrogen, causing your waistline to expand, and stress hormone cortisol levels begin to rise. High cortisol levels stimulate muscle breakdown and cause fat to build up around your belly. In short: the spread of middle age.
