Metabolism is a complex and fascinating process—your body’s way of using energy and burning calories. It works tirelessly, 24/7, to keep you alive, transforming the food and nutrients you consume into the energy needed for breathing, cell repair, circulation, and all the essential functions that sustain life.
Metabolism consists of anabolic processes that build and require energy, and catabolic processes that break down substances and use energy. The calories your body burns come from carbohydrates, fats, and proteins. Even when you’re at rest, your body is constantly using energy—this is called your basal metabolic rate (BMR), which accounts for 50-70% of your total energy expenditure.
Metabolic speed varies from person to person, influenced by factors such as age, gender, body composition, genetics, climate, diet, and physical activity. For instance, individuals with greater muscle mass tend to burn more calories because muscle cells require more energy than fat cells. This is why building muscle is such a powerful tool for metabolic health.
Does metabolism really slow down at midlife?
According to recent scientific research, metabolic rate remains stable from early adulthood until around 65 years old—which contradicts the common belief that metabolism slows down during perimenopause. However, the study didn’t fully account for factors such as insulin sensitivity, hormonal shifts, and muscle mass changes, all of which significantly impact metabolism.
How perimenopause influences weight and metabolism?
While metabolism itself may not decline, hormonal changes during perimenopause can influence body composition, appetite, and fat distribution. Several key factors come into play:
- Loss of Muscle Mass
As oestrogen levels decline, muscle loss accelerates, especially in women who do not engage in strength training. Without resistance exercise, muscle mass naturally decreases by about 4% per decade after age 35. However, once oestrogen levels drop significantly, this process speeds up even more. Since muscle is metabolically active, losing it means burning fewer calories, making weight management more challenging. - Weakened Insulin Sensitivity
Oestrogen plays a key role in insulin sensitivity, helping the body efficiently process carbohydrates and fats. As its levels decline, the body becomes less responsive to insulin, increasing the risk of insulin resistance and type 2 diabetes. This is often accompanied by an increase in abdominal fat storage, a common issue in perimenopause. When insulin sensitivity weakens, the body struggles to process sugars and fats as efficiently, leading to weight gain—especially around the midsection. - Changes in Fat Distribution
Hormonal shifts during perimenopause affect where fat is stored. Instead of accumulating primarily on the hips and thighs, fat begins to concentrate around the abdomen and internal organs. This type of visceral fat is metabolically different from subcutaneous fat and is associated with greater health risks. The decline in oestrogen and rise in cortisol contribute to this redistribution, alongside changes in gut microbiome health and sleep patterns. - Increased Appetite & Leptin Sensitivity
Oestrogen plays a regulatory role in appetite, helping to reduce hunger and enhance satiety by increasing leptin, the hormone responsible for signalling fullness. As oestrogen declines, leptin production decreases, leading to increased hunger and cravings. This is similar to the second phase of the menstrual cycle, when many women experience a greater appetite. Interestingly, while women with higher body fat levels naturally produce more leptin, those who are overweight often develop leptin resistance, meaning the hormone no longer signals fullness as effectively. This can lead to increased appetite despite higher leptin levels, making weight management more challenging. Even women with a normal weight but low muscle mass can have higher leptin levels yet struggle with appetite control, highlighting the importance of muscle-building activities for overall metabolic health.
Embracing Metabolic Wellness
While perimenopause brings changes, it is not an inevitable road to weight gain or metabolic slowdown. By prioritizing muscle-building exercise, nourishing foods, balanced blood sugar, quality sleep, and stress management, we can support our bodies through this transition with grace and strength.
Rather than seeing these changes as limitations, we can reframe them as invitations—opportunities to nurture ourselves more deeply, to listen to our bodies with greater wisdom, and to move through this phase of life with resilience and vitality.