Khaberni - Some individuals blame aging and slowing metabolism for their weight gain in middle age, and resign to their extra weight as if it were an inevitable fate, so the solution becomes buying new clothes instead of those that have become tight, and they continue to console themselves that this is the law of life.
So, is weight gain in middle age really an inevitable fate? And is slowing metabolism the only reason for weight gain?
Amid a flood of health advice and fluctuations in nutrition patterns, Dr. Matthias Viehvari, a consultative obesity surgeon at Nuffield Health in the United Kingdom, with extensive experience in metabolism issues, provides clarification on this for The Independent newspaper.
What is Metabolism?
"Metabolism is the chemical processes that maintain our body functions, from converting food into energy, repairing cells, and supporting organ functions," says Viehvari.
The metabolic rate expresses the amount of energy that the body uses to maintain these vital processes.
Viehvari adds, "Even while resting, your body still works to maintain your heart rate, your lung breathing, and your brain activity, and this is known as the basal metabolic rate."
Misconceptions About Metabolism
A common misconception is that metabolism alone determines body weight, clarifies Viehvari: "Weight regulation is formed through a complex network of factors that extend beyond calorie burning, including dietary quality, muscle mass, sleep, and physical activity, in addition to deeper physiological mechanisms like changes in bile flow, stomach function and size adjustments, vagus nerve signals, and gut hormone modulation."
The gut microbiome also plays a vital role, affecting how efficiently we extract energy from food, how bile acids are processed, and generally how our metabolism functions.
Some people assume that metabolism steadily declines after early adulthood, but this is inaccurate, says Viehvari: "Wide-ranging and high-quality studies show it remains remarkably stable for decades before gradually slowing later in life."
How Does Metabolism Change with Age?
"The metabolic process is not a straight downward curve, as an important study published in Science in 2021, which included more than 6,000 people, showed that energy expenditure peaks in childhood—where it can be 50% higher than in adults—then gradually decreases until about age twenty," says Viehvari.
The metabolic rate remains notably stable when adjusted according to body size and composition from the twenties to about sixty, and after sixty, the metabolic rate tends to decline slowly but measurably.
What are the Reasons for this Decline from Sixty Onwards?
After the age of sixty, the metabolic rate usually decreases by about 0.7% yearly. The main reasons are loss of muscle mass, decreased physical activity, and minor hormonal changes such as declining levels of growth hormone and sex hormones," says Viehvari.
The efficiency of mitochondria—the body's energy production mechanism—may also decrease slightly with age. This does not mean that the body forgets how to burn energy, but that it becomes less efficient at doing so.
What Lifestyle Factors Affect Metabolism?
Many lifestyle habits can support or slow down metabolic function.
Muscle Mass Decrease or Inactivity
"Muscle tissue burns more energy than fat, even at rest," explains Viehvari.
Following a Strict Diet
"Severe caloric restriction can temporarily inhibit the metabolic rate," explains Viehvari.
Lack of Sleep
"Lack of sleep can affect hunger and energy-regulating hormones such as leptin and ghrelin," indicates Viehvari.
Chronic Stress
"High cortisol levels can enhance fat storage and affect energy usage," says Viehvari.
