How to boost your metabolism after 40: Science-backed ways to feel energised again

Getting older comes with its share of benefits, from increased confidence to greater wisdom. But it can also mean a few changes that perhaps aren’t quite as welcome: grey hairs, wrinkles and fine lines, achy joints and a slower metabolism.

Metabolic slowdown is part of the ageing process, but it is possible to support your metabolism and reduce some of its effects. Here’s how.

Why does metabolism slow down with age?

In simple terms, your metabolism is the collection of bodily processes that convert food into energy. You need that energy to fuel all of your bodily functions, from breathing to walking. 

Your metabolism slows down as you get older due to a range of factors, including:

• Age-related muscle loss: As you get older, your body starts to lose muscle mass. This process kicks off around age 30, when you start losing about 3-8% of total muscle mass each decade, then accelerates at age 60.[1] Muscle requires a lot of energy to maintain, and with less of it, your body simply isn’t as efficient at using up energy
• Hormonal changes: Getting older also means your testosterone and estrogen levels shift, contributing to muscle loss. These hormonal changes can also change your body composition, making your body store more fat than muscle
• A more sedentary lifestyle: It’s very normal for physical activity to decrease with age, especially if you’re in a desk job or have less time for structured exercise. This can further slow your metabolism
• Reduced growth processes: In early life, your body is growing muscle, bones, organs, connective tissue and new cells. This requires huge amounts of energy. In older age, many of these processes slow down or stop entirely
• Cellular changes: The cells in your body become less efficient at using energy over time, meaning you don’t need as many calories to function
• Lifestyle factors: Other lifestyle factors like chronic stress, poor sleep, excessive alcohol intake and poor dietary habits can contribute to a slower metabolism.

When you’re younger, you simply have more muscle mass, more efficient cells, more growth processes going on throughout your body, and you may be exercising more – all of which means your body burns calories at a faster rate.

The impacts of a slow metabolism

A slower metabolism doesn’t mean you’re guaranteed to gain weight, but for many people, that’s often one of the biggest impacts.

Your basal metabolic rate refers to the minimum number of calories your body needs to perform basic functions. As you get older, this number goes down – largely because of age-related muscle decline and other changes that reduce your overall energy expenditure.

This means your body needs fewer calories compared to when you were younger. If your eating habits stay the same but your energy requirements decrease, excess energy may end up being stored as body fat.

The important thing worth mentioning here, though, is that metabolism alone isn’t responsible for weight gain. Weight management generally comes down to calories in (the energy you consume) versus calories out (the energy you burn, usually through exercise).

Using more calories than you consume can help you lose weight, while eating more than you use may contribute to weight gain. So, if you continue eating the same number of calories but your body isn’t able to use them as efficiently, they can get stored as fat. 

Signs your metabolism may be slowing down

To figure out whether your metabolism is slowing, there are a few signs to look out for:

• It’s harder to lose weight: Despite all your best efforts with a modified diet and increased exercise, you may be gaining weight or finding it harder to lose weight – this could indicate that your metabolism is slowing
• You’re tired: When your body isn’t as efficient at extracting energy from food, it can make you feel more lethargic
• You have dry skin, brittle nails and thinning hair: When your body is trying to conserve energy and prioritise essential functions, it might divert less energy to functions that aren’t as critical for survival, like skin repair and maintenance, hair and nail growth.
• You feel colder than usual: Your metabolism generates heat due to the energy produced during different metabolic processes. When it slows down, your body temperature may drop along with it, making you feel unusually cold
• Your digestion is slower: Metabolism supports a healthy and efficient digestive system, so if you’re noticing signs of sluggish digestion – like constipation, bloating, gas and abdominal discomfort – it may indicate your metabolism is slowing

Foods and habits that slow metabolism down

Even though a slower metabolism is a normal part of ageing, some habits may be exacerbating its effects. These include:

• Eating certain foods: Foods like refined carbs (white bread, white rice, pastries) are incredibly low in fibre, meaning your body digests them very quickly. This can trigger insulin and blood sugar spikes, which may contribute to insulin resistance and metabolic dysfunction and turn into a gradual metabolism slowdown over time
• Drinking excessively: Drinking alcohol in excess can overload your liver, which is a key part of your metabolic processes. Chronic drinking can make your body less efficient at burning energy. The UK Chief Medical Officers advise against regularly drinking more than 14 units a week, ideally spread over three or more days [2]
• Crash dieting: Crash diets typically rely on severe calorie restriction to help you lose weight. Among other issues, crash dieting can contribute to a slower metabolism as it pushes your body into famine mode – making it more likely to conserve energy
• Not challenging your muscles: Because muscle uses more energy than fat, not using and strengthening them can slow your metabolism
• Chronic stress: Short-term stress can actually increase your metabolism as your body mobilises energy stores during the fight-or-flight response. But chronic stress has the opposite effect, as it encourages your body to conserve energy, making it less efficient
• Poor sleep quality: A lack of quality sleep has a profound effect on the hormones that control hunger and satiety, along with your body's ability to use energy efficiently. When these are disrupted, it can negatively affect your metabolism

How to boost metabolism after 40

As you get older, a certain amount of metabolism slowdown may be expected. The good news is, though, there are several things you can do to try and boost it.

Prioritise protein at every meal

When you eat, some of the calories you consume are used to digest your food – this process is called the thermic effect of food (TEF). Of all the macronutrients (fat, carbohydrates, protein), protein requires the most energy to be digested.[3]

Protein is also an essential building block for your muscles and helps you stay fuller for longer by triggering the release of certain hormones.

That’s why it should be a key part of every meal. Aim to get about 25-30g of lean protein per meal – this could be a single chicken breast, 250g of Greek yoghurt, 1½ cups of legumes or a palm-sized piece of fish.

Add thermogenic foods to your diet

Thermogenic foods are those that temporarily raise your body temperature, requiring more energy to digest them. This can briefly increase energy expenditure.

High-protein foods are considered thermogenic foods, but there are many others to consider: spices (chilli, ginger, cinnamon), caffeine (coffee, tea, cocoa), high-fibre foods (whole grains, veg, fruit), and foods rich in certain minerals like iron, iodine and selenium.

Increase your daily physical activity to burn calories

Moving your body supports a faster metabolism in a couple of ways. 

First, it uses up calories immediately, as you can burn a lot of energy during exercise.

Second, it increases something known as resting energy expenditure – the energy you use when you’re not moving at all. It’s estimated that you burn 60-75% of calories while resting, so a small increase in resting energy expenditure can be pretty significant.[4]

To get the full benefits, aim to exercise at least three days each week. High-intensity exercise like running, jogging and high-intensity interval training are all great, but even moderate activities such as cycling and swimming are beneficial.

Build muscle with strength training

We know muscle is essential for burning energy efficiently, so it only makes sense that you’d prioritise it as you get older.

Strength training should form an essential part of your regular exercise routine. It helps preserve your muscle mass, as well as build new muscle, which can in turn boost your metabolism.

Many experts recommend 2-3 sessions of strength training each week.[5] Sessions could include body weight exercises like squats and lunges, lifting weights, using weight machines, or resistance training with bands and cables.

Stay hydrated

Adequate hydration supports a number of bodily functions, including your metabolism. It supports many of the metabolic processes that happen when your body digests food, such as fat breakdown, energy production, waste elimination and transporting nutrients around your body. It’s also considered a thermogenic substance, meaning it can temporarily boost calorie burning.[6]

Naturally, staying hydrated may support your metabolism as you get older. The NHS suggests aiming for 6 to 8 cups or glasses of fluid a day. Water, lower-fat milk, and tea and coffee all count. You may need more if you’re exercising or it’s hot.[7]

Improve sleep quality

Getting enough sleep is an essential pillar for overall health, but it can also help with regulating your metabolism. When you experience poor sleep, the appetite hormones ghrelin (which stimulates hunger) and leptin (which controls satiety) are disrupted. 

This can make you feel hungrier and lead to more cravings for high-calorie, highly processed foods. Chronic sleep deprivation can impact how your body processes blood sugar and even contribute to muscle loss – both of which can negatively affect metabolic health.[8]

To improve your sleep, a few simple strategies may help. Try to go to bed and wake at the same times each day (even on weekends), cut screens about an hour before bedtime, avoid caffeine in the afternoon, steer clear of alcohol and heavy meals before bed, and make your sleep environment dark, cool and quiet. Aim to reduce stress, too – this can have a massive effect on your sleep quality.

Consider supplements

No single supplement will transform your metabolism, but some may offer modest or supportive benefits.[9] The most popular ingredients in fat metabolism-boosting supplements include:[10]

• Green coffee bean extract
• Green tea extract
• Bitter orange
• Carnitine
• Conjugated linoleic acid
• Forskolin
• Chromium
• Kelp
• Fucoxanthin

Keep in mind that the evidence that these supplements work is fairly limited, so they may have little to no effect.

When to speak to a healthcare professional

The signs of a slowing metabolism we mentioned earlier may be common, but if they’re persistent or severe, reach out to a healthcare professional. You may notice:

• Rapid or unintentional weight loss
• Severe chronic fatigue
• Extreme temperature sensitivity
• Physical changes like hair thinning, extremely dry skin, muscle weakness or brain fog
• A waist circumference of 80cm or more (or 94cm for men)

Your GP or dietitian can assess your overall health and symptoms to work out whether these symptoms indicate something more serious, like insulin resistance, hypothyroidism (underactive thyroid) or metabolic syndrome.

Need support with losing weight?

If you’ve hit a metabolic slowdown and noticed it’s impacting your weight, Juniper has your back.

The Juniper Programme combines ongoing guidance from a team of health experts with breakthrough weight loss medications like Mounjaro or Wegovy to help you lose weight and keep it off.

You’ll get a personalised exercise program to support your metabolism, a diet plan that enables sustainable weight loss, and ongoing expert support across your entire weight loss journey from Juniper’s companion app.

Your weight loss medication is also delivered discreetly to your door, making the program convenient and accessible.

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