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You’re not alone if you’ve ever been told your metabolism “falls off a cliff” after 30. It’s a common belief that ageing brings an inevitable energy slump, making it harder to feel good in your body. But what if that’s not quite how it works?
A major international study published in Science in 2021 helped set the record straight. Researchers analysed metabolism data from more than 6400 people from infancy to age 95. They found our resting metabolic rate is remarkably stable from our 20s to our late 50s. It wasn’t until after age 60 that a meaningful decline occurred, and even then, it was only about 0.7% per year. So why do we feel as if things change earlier?
The answer often lies in how we live, not our metabolic functioning. In our 30s and 40s, many become more sedentary, experience more stress, eat rushed meals while juggling family demands and get less sleep. These changes affect how energised we feel and are often mistaken for a “slowing metabolism”.
Still, we do gradually lose muscle mass throughout adulthood, a process known as sarcopenia. This can start in our 30s and is more pronounced in older age. Sarcopenia increases frailty, falls and fractures in older age, so staving off muscle loss in young adulthood is in our best interests. And given that muscle tissue burns more energy at rest than fat tissue, maintaining muscle mass during adulthood also helps support our metabolic health.
While research shows that consistent resistance training and physical activity in adulthood reduce the risk of sarcopenia, less is known about how nutrition quality across a lifetime shapes our risk in later years.
A 2023 study published in the American Journal of Clinical Nutrition found that people who ate more whole foods in early adulthood had greater muscle mass and a lower risk of sarcopenia in midlife. So what we eat in our 20s and 30s likely supports muscle health decades later. The quantity of food we eat is also important, because if we don’t eat enough, the body may break down muscle to meet energy needs (as users of Ozempic for weight loss and diabetes are discovering).
Protein plays a key role, but so, too, do vitamin D, omega-3 fats and antioxidants such as selenium and carotenoids in supporting muscle health by helping reduce inflammation and oxidative stress. These nutrients are often abundant in whole foods such as vegetables, legumes, oily fish and whole grains.
While there is a tendency to focus on protein or other singular nutrients as a muscle fix, emerging research on sarcopenia prevention is shifting from a single nutrient focus to whole-diet patterns. Whole-food-focused dietary patterns (such as the Mediterranean diet) are rich in diverse, nutrient-dense foods that better support muscle function, gut health and inflammation.
So, rather than trying to “fix” our metabolism, it may be more helpful to focus on what we know helps:
Move regularly: Resistance-based exercise such as weights, Pilates or yoga helps to maintain muscle. Walking, gardening or climbing stairs are good activities – do what you enjoy.
Eat well: Prioritise whole foods with protein, healthy fats, fibre-rich wholegrains and plenty of colourful fruits and vegetables.
Sleep enough: Adults need around 7–9 hours to support recovery and hormonal balance.
Manage stress: Chronic stress affects our appetite, sleep quality, muscle maintenance and more. Rest, recreation and social connection can all help in managing stress.
So, it’s time to shift the narrative.
Your body and metabolism aren’t failing you; they’re responding to your world. Often, what changes in adulthood isn’t just your biology but the pressures, pace and patterns of modern life. It’s less about fixing a problem and more about focusing on your overall wellbeing through regular enjoyable movement, nourishing food, restorative sleep and giving yourself time to unwind.
The goal isn’t controlling and hammering your body and metabolism into shape but caring for your body and wellbeing. Because health in adulthood isn’t about pushing harder, it’s about listening more closely.
It’s listening to your body when you experience hunger and responding by providing a nourishing meal rather than ignoring it to meet a work deadline. Or when you feel physically drained, choosing to rest or have an early night, rather than continually pushing yourself through the fatigue at work, the gym, or while juggling parenting responsibilities, and then ending up sick.
As well as Jennifer Bowden’s columns in the NZ Listener, listener.co.nz subscribers can access her fortnightly myth-buster column which explores food and nutrition myths.
