Many of us have, at some point, pointed the finger at our metabolism when discussing weight. However, the intricate system responsible for converting the food we eat into energy is far more complex than simply being 'fast' or 'slow', according to leading experts. Dr Richard Mackenzie, a biomedical researcher and author based at The Metabolic Health Clinic in London, emphasises that metabolism encompasses all chemical processes within the body that facilitate energy conversion, tissue repair, hormone regulation, and essential bodily functions.
Dr Mackenzie highlights the importance of looking beyond just calorie expenditure. "A broader and more useful perspective is to think about metabolism as involving both energy expenditure and metabolic health, which means how effectively the body processes and responds to nutrients," he explains. Contrary to popular belief, metabolism doesn't typically slow down significantly until after the age of 60. Even then, an individual's lifestyle habits are often the primary driver behind how many calories they burn.
Hormones play a critical role in regulating metabolism. Insulin, produced by the pancreas, is key to moving glucose from the bloodstream into cells. If cells become less sensitive to insulin, a condition known as insulin resistance, this process becomes inefficient, leading to increased fat storage, particularly around the waist. This can elevate the risk of metabolic syndrome, a cluster of conditions including high blood pressure, unhealthy cholesterol levels, abdominal obesity, and raised blood sugar, which in turn increases the risk of type 2 diabetes, heart attack, and stroke.
For women, fluctuating hormone levels during perimenopause and menopause can significantly impact metabolism. Dr Mackenzie notes that declining oestrogen levels can promote fat storage, especially around the waist, and may lead to a more rapid decrease in muscle mass and worsening insulin sensitivity. This often results in weight gain, even without significant changes in calorie intake. While hormone therapy (HRT) has been shown to improve insulin sensitivity and help reduce abdominal fat associated with menopause, it is not primarily recommended as a weight-loss treatment.
Other factors, such as thyroid hormones, also contribute. Low levels of thyroid hormones (hypothyroidism) can slow down metabolism, potentially leading to weight gain. Beyond hormonal influences, lifestyle choices are paramount. Experts suggest that boosting muscle mass, staying physically active, maintaining a balanced diet, ensuring adequate sleep, and effectively managing stress levels are all crucial for supporting a healthy metabolism. Conversely, a poor diet, excessive snacking, and a reliance on processed foods can negatively impact metabolic health.