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Many of us attribute gradual weight gain in middle age and beyond to a slow metabolism, but to what extent is this assumption true? In a world flooded with health advice and ever-changing diet trends, we consulted Matyas Fehervari, a consultant bariatric surgeon at Nuffield Health in the UK, who works extensively with metabolic issues, to cut through all the noise. He has helped demystify exactly what a metabolism is, how it can change with age and some key ways we can maintain a healthy metabolism as we get older. “Metabolism refers to the chemical processes that keep our bodies functioning – from converting food into energy to repairing cells and supporting organ function,” Fehervari says. “The metabolic rate is the amount of energy your body uses to maintain these vital processes. “Even when you’re resting, your body is still working to keep your heart beating, lungs breathing and brain active – this is known as your basal metabolic rate (BMR).” “One of the biggest myths is that people with a ‘fast’ metabolism can eat whatever they like without gaining weight,” Fehervari says. “In reality, differences between individuals are usually modest.” Another common misconception is that metabolism alone determines body weight. “Weight regulation is shaped by a complex network of factors extending far beyond calorie burning,” Fehervari says. “These include diet quality, muscle mass, sleep and physical activity, but also deeper physiological mechanisms such as changes in bile flow, adjustments in stomach function and size, nerve (vagal) signalling and the modulation of gut hormones. “The gut microbiome also plays a vital role, influencing how efficiently we extract energy from food, how bile acids are processed, and how our metabolism functions overall.” Some people assume that metabolism steadily declines after early adulthood. Fehervari says studies show it remains remarkably stable for decades before gradually slowing later in life. “Metabolism isn’t a straight downward curve,” Fehervari says. “A major study published in Science in 2021, involving over 6,000 people, showed that energy expenditure peaks in infancy – when it can be over 50 per cent higher than in adults – then gradually declines until around age 20.” “From the 20s through to around 60, metabolic rate remains remarkably stable when adjusted for body size and composition. After 60, there tends to be a slow but measurable decline.” At that age, the metabolic rate typically declines by about 0.7 per cent each year, he says. The main reasons are loss of muscle mass – known as sarcopenia – reduced physical activity and subtle hormonal shifts such as lower levels of growth hormone and sex hormones. “Mitochondrial efficiency – the body’s energy-producing machinery – may also decline slightly with age. It’s not that your body ‘forgets’ how to burn energy; rather, it becomes a little less efficient at doing so,” he adds. Several lifestyle habits can support or slow metabolic function. Having low muscle mass or being inactive will slow it, Fehervari says. “Muscle tissue burns more energy than fat, even at rest.” Crash dieting will slow it, too. “Severe calorie restriction can temporarily suppress metabolic rate.” Not getting enough quality sleep also slows it down. “Poor sleep can alter hunger and energy-regulating hormones such as leptin and ghrelin.” A state of chronic stress is bad for mental and physical health, as it elevates cortisol levels, which “can promote fat storage and affect energy use”, Fehervari says. Two other habits worth curbing are smoking and drinking too much, as they “can both impair cellular metabolism and hormone balance”. Is it actually possible to “boost” your metabolism? “There’s no magic pill or quick fix,” Fehervari says. “Temporary increases in energy expenditure can occur after exercise or with caffeine, but these are modest. “The most effective, evidence-based way to maintain a healthy metabolism is to preserve muscle mass and stay active throughout life.” 6 ways to safeguard metabolism function Here are tips to keep our metabolism levels stable as we get older, according to Fehervari. Stay active. “Combine aerobic activity like brisk walking or cycling with resistance training to maintain muscle.” Prioritise protein. “Eat enough protein, especially in later life, to support muscle repair and prevent sarcopenia.” Avoid extreme diets. “Sustained, balanced nutrition keeps metabolic processes steady.” Sleep well. “Aim for seven to nine hours [of sleep] to support hormonal and energy balance.” Manage stress. “Mindful activities and social connections reduce cortisol’s long-term effects.” Have regular check-ups. “Thyroid, vitamin D and hormonal imbalances can all influence energy metabolism, so I would recommend regular check-ups.” Fehervari reminds us that our metabolism does not inevitably crash with age; it remains stable for decades and only begins to slow slightly after around 60. “Much of that change is due to muscle loss and lifestyle, not age alone,” he says. “By staying active, eating well and maintaining strength, most people can keep their metabolism healthy well into later life.” Like what you read? 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