Having more fat and less muscle reduces calorie burning. Many people also become less active with age for various reasons, which further slows the number of calories you burn. Age isn't the only thing that determines your metabolic rate, however — your body size and sex play a role.
A Monash University scientist has discovered key appetite control cells in the human brain degenerate over time, causing increased hunger and potentially weight-gain as we grow older. The research by Dr Zane Andrews, a neuroendocrinologist with Monash University's Department of Physiology, has been published in Nature.
In Your 40s
—digestion issues are more likely to show up, Bhatia says, which will understandably mess with your appetite. But your 40s may also be a decade of slowing down physically. "Appetite typically increases out of proportion to activity level," she says.
Other reasons you may notice an increased appetite include emotional eating, a physical health condition like hypothyroidism, or a mental health condition like clinical depression. If you're concerned about a sudden increase in appetite, reach out to your healthcare provider.
Why We Gain Weight As We Age It starts sometime during our 50s and 60s: that belly bulge, those "extra" pounds we just can't seem to shed. Part of it is simply the biology of our bodies. Our muscles literally shrink as we age, and that means more calories turn into fat — and it's a lot harder to exercise it off.
Although the prevalence of obesity increases with age, weight gain is actually greatest across the younger years of adult life — late twenties and thirties — and diminishes gradually over time as adults get older, says Tucker.
“Obesity incidence starts increasing in one's twenties and peaks at 40 to 59, and then decreases slightly after age 60,” says Craig Primack, MD, an obesity medicine physician at the Scottsdale Weight Loss Center in Arizona.
Often known as the “hunger hormone,” ghrelin has numerous functions in addition to telling your brain you're hungry. For example, ghrelin: Increases food intake and helps your body store fat. Helps trigger your pituitary gland to release growth hormones.
As estrogen declines in perimenopause and menopause, appetite ramps up. Poor sleep. During perimenopause and menopause, hormone weirdness can impact your sleep ( perimenopause night sweats, for example). Insufficient sleep can further elevate sensations of hunger.
"The intense phase of the growth spurt goes on for about three years, from ages 12 to 15 years for boys and 10 to 13 years for girls." An appetite surge isn't the only telltale sign. There are also growing feet, more body hair, and roller-coaster emotions.
A significant amount of the body's growth begins to take place around ages 10-12 and peaks around 13-14. Because a teen's body is growing and developing so much at this time, they have higher metabolic needs. This means they need more calories and more vitamins and minerals, especially certain ones like calcium.
After 40, your hormone levels (estrogen) drop. This causes your insulin (hormone that helps your body use sugar) rise. Your thyroid levels go down. This combination makes you hungrier.
Cortisol (a stress hormone) and insulin (a hormone that regulates blood sugar) can also contribute to midlife hunger pangs. While they may not be directly associated with menopause, insulin and cortisol can become off-balance in midlife. Research shows that this, too, can contribute to an increase in appetite7 .
Overall, a combination of lifestyle changes, such as dietary modifications, exercise, stress management, and adequate sleep, is key to reducing hormonal belly fat effectively. In some cases, hormone replacement therapy or body shaping procedures may also be considered.
The hormone leptin is produced by fat cells and is secreted into our bloodstream. Leptin reduces a person's appetite by acting on specific centres of their brain to reduce their urge to eat. It also seems to control how the body manages its store of body fat.
Your body then lacks the metabolic energy to function optimally, and efficiency decreases. For example, those affected experience weight gain, sensitivity to cold, dry skin, and fatigue. If you've noticed that you often feel hungry and you've gained weight, you may have hypothyroidism.
Oestrogen and fat distribution
Reduced levels of oestrogen after menopause can cause fat to be stored around your waist rather than on your hips and thighs. In postmenopausal women, belly fat accounts for 15 to 20% of their total body weight, compared with 5 to 8% in premenopausal women.
We also lose height as the discs between our vertebrae compress, shrinking the vertical space in our abdominal cavity and expanding it outward. Finally, the loss of estrogen after menopause causes a slight shift of fat to the abdominal region.
The finding of the study suggests that people in middle age certainly gain weight and it is harder for them to lose it, but slow metabolism is not the real reason behind it. It was revealed that from the 20s to the 50s the energy expenditure is the most stable.
Summary. For many people, the term metabolism really means metabolic rate — the speed at which your body burns calories to keep its basic functions running. Your metabolic rate does change during your early life, but it plateaus between the ages of 20 and 60, and only decreases by around 1% per year after that.
Men often gain weight until about age 55, and then begin to lose weight later in life. This may be related to a drop in the male sex hormone testosterone. Women usually gain weight until age 65, and then begin to lose weight.
Because men have higher levels of testosterone (which can lead to lipolysis, or fat-burning) and lower levels of estrogen, they tend to accumulate fat in their bellies; women, on the other hand, have higher estrogen levels, so they tend to store more fat in their legs and hips.