1. Estrogen Decline in Women
For women, the years leading up to menopause (perimenopause) bring a decline in estrogen production. This is one of the primary reasons women begin gaining weight, especially around the abdomen.
Low Estrogen Level Affects Metabolism in Women:
Metabolism is the process that occurs from digestion, the breakdown of food into tiny, microscopic molecular parts, and absorption, when the tiny food molecules enter the cell.
Low estrogen levels can lead to all of the following:
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- Increase in belly fat storage (visceral fat). Low estrogen increases the possibility of an increase in belly fat storage, which in turn increases the chances of chronic diseases, such as heart, kidney, metabolic, especially diabetes, and many other chronic conditions.
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- Slows calorie burning – Low estrogen promotes a reduction in metabolism and the burning of calories, causing the body to store the resulting extra calories as fat, particularly in the abdominal cavity. People call this “Belly Fat”. This type of fat is hard to lose and can lead to all kinds of serious health issues. In fact, this fat can even become calcified when the fat cells die, forming hard deposits in some people, meaning that the fat changes into a living”rock.” This is very dangerous, especially if this happens near the abdominal aorta.
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- Causes insulin resistance, and more sugar is stored as fat. Insulin is a hormone made by the pancreas. Its job is to help move digested food into cells and to help store extra digested food as fat. When cells resist insulin, the food digested cannot enter the cells, causing a spike in blood glucose (blood sugar). Glucose is the product of the breakdown of carbohydrates. Glucose plays a vital role in cellular energy production. When the cell is insulin-resistant, glucose cannot enter the cell, and energy cannot be produced.
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- Creates cravings for carbs and sweets – due to the fact that cells are deprived of sugar, as explained above. I mean, the sugar circulates in the blood but cannot enter cells due to insulin resistance. The person craves the missing glucose that never made it in.
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- Leads to increased fatigue and slower recovery – also, as explained above, if glucose doesn’t enter the cells, they cannot produce energy as glucose is broken down to make energy. If cells don’t make energy, the person will feel tired and fatigued and has problems recovering from illnesses including the insulin resistance.
Women often say:
“I’m gaining weight even though I’m eating the same things.”
This is usually due to estrogen fluctuations, not overeating.
2. Testosterone Decline in Men
Testosterone is a male sex hormone that determines a male’s characteristics, such as growth and fertility. This hormone’s production declines with age.
Men also experience hormonal changes after 40. Testosterone levels begin decreasing about 1% per year after age 30, but the effects become more noticeable after 40.
How Low Testosterone Impacts Metabolism:
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- Loss of muscle mass. One of the first effects of low testosterone is loss of muscle cells. Men tend to have more muscle than women, but when there’s a decline in testosterone in men, this characteristic of men is affected.
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- Slower fat burning – The ability to burn fat is decreased with less muscle and as a direct effect of low testosterone.
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- Increased belly fat – Low testosterone encourages
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- Lower energy and motivation
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- Reduced metabolic rate
Because muscle is the body’s top calorie-burning tissue, losing it means the metabolism naturally slows down, even if diet and activity stay the same.
3. Increased Cortisol (The Stress Hormone)
Adults over 40 tend to juggle more responsibilities—careers, families, finances, aging parents. These stressors can cause chronic elevation of cortisol, the hormone released during stress.
High Cortisol Has Several Metabolic Effects:
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- Increases appetite
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- Encourages belly fat storage
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- Slows down metabolism
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- Causes fatigue and poor sleep
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- Promotes sugar cravings
This is why stressed, exhausted adults often gain weight even when they’re eating less.
4. Insulin Changes and Blood Sugar Imbalances
As we age, the body becomes less efficient at using insulin, the hormone that moves sugar into cells for energy. This condition is called insulin resistance, and it’s one of the biggest contributors to weight gain after 40.
Signs of Insulin Resistance:
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- Stubborn belly fat
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- Cravings after meals
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- Feeling tired after eating
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- Slow weight loss
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- High blood sugar
When insulin isn’t working properly, your body stores more fat—especially around the abdomen.
5. Thyroid Hormone Slowdown
Thyroid hormones control your metabolic speed. Even slight changes can make a significant difference.
As we age, thyroid hormone production can slow down, resulting in:
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- Weight gain
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- Fatigue
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- Slowed digestion
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- Feeling cold
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- Hair thinning
Millions of adults have mild thyroid changes that go undiagnosed.
The Bottom Line: Hormones Run the Show
When hormones shift, metabolism shifts—and that’s exactly what happens after 40.
The good news?
You can support your hormones naturally through:
✔ strength training
✔ nutrient-rich foods
✔ better sleep
✔ stress reduction
✔ balanced protein intake
✔ healthy hydration
✔ avoiding ultra-processed foods
These habits help rebalance the hormones that control metabolism so your body can burn fat more efficiently and maintain a healthy weight.
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- Natural drop in muscle mass
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- Slower calorie-burning rate
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