How to speed up your metabolism: what works and what does not

You cannot speed up your metabolism much, but you can stop it slowing down. Your resting metabolism depends mostly on your size and how much muscle you carry, and a 2021 study in Science found it holds steady from age 20 to 60. Strength training twice a week, enough protein, more daily movement and good sleep protect it.

When people say their metabolism has slowed, they usually mean they are gaining weight without eating more. The cause is often less muscle, less movement or poor sleep, and sometimes something a blood test can pick up. Four questions will show you where to start.

Can you speed up your metabolism?

Not by much. Metabolism is the energy your body uses each day, and most of it goes on keeping you alive at rest: your heart, brain, liver, kidneys and muscles. The rest goes on movement and on digesting food.

Bigger bodies and bodies with more muscle use more energy. That is why the main levers are building muscle and moving more, not a particular food or supplement.

The idea that metabolism falls off a cliff at 30 or 40 is not what the data show. Herman Pontzer and colleagues pooled measurements from a large international database of people aged 8 days to 95 years, using the doubly labelled water method, the gold standard for measuring energy use in daily life. Once they adjusted for body size and muscle, energy use stayed steady from about 20 to 60 and only declined after that.

Why your metabolism seems to slow

If energy use is steady through midlife, why does weight creep up? Usually because something else changed.

Less muscle

Muscle uses energy even at rest. When you lose it, through inactivity, ageing or crash dieting, your daily energy needs drop with it.

“When muscle mass decreases and fat mass increases this leads to less overall daily energy expenditure, despite no change in the level of physical activity. Meaning if you continue to keep eating the same foods and doing the same exercise, these changes are still possible.”
Dr Michelle Woolhouse, Vively Medical Director

Weight loss itself

When you lose weight, your body uses less energy, partly because it is smaller and partly because it adapts. The extreme example is a US study of 14 contestants from The Biggest Loser (Fothergill 2016). By the end of the 30-week show, their resting metabolism had fallen by an average of 610 kcal (about 2,550 kJ) a day. Six years later it was still 704 kcal (about 2,950 kJ) a day lower than at the start, even though most had regained much of the weight.

That was rapid, extreme weight loss, and most people will see far smaller changes. It is one reason to favour slower loss with strength training, which helps you hold on to muscle.

Moving less

Everyday movement, such as walking, climbing stairs, standing and fidgeting, is the part of your energy use you can change most easily. It also falls quietly when work gets busier or a commute turns into working from home.

Short sleep

Sleep changes how your body handles a diet. In a small, tightly controlled study, 10 adults on the same reduced-energy diet slept either 8.5 or 5.5 hours a night for two weeks (Nedeltcheva 2010). With short sleep, the share of weight lost as fat fell by 55%, they lost 60% more lean mass (2.4 kg against 1.5 kg) and they were hungrier.

After 60

From about 60, energy use does start to fall, even after accounting for body size. Keeping muscle matters more from here, which is why protein needs rise after 70.

What actually helps

The things that protect your metabolism are unglamorous and they work over months, not days.

• Strength training: Australia's physical activity guidelines include muscle-strengthening activity on at least 2 days a week, on top of 2.5 to 5 hours of moderate activity. Bodyweight exercises, bands, weights and Pilates all count.
• Protein: the NHMRC recommends 0.84 g per kg of body weight a day for men and 0.75 g for women, rising to 1.07 g and 0.94 g after 70. Spread it across meals. Our list of high protein foods makes that easier.
• Less sitting: the same guidelines warn that long periods of sitting can offset the benefits of exercise. Break them up with short walks.
• Sleep: seven hours or more gives your diet and training a better chance of taking fat rather than muscle.
• Lose weight slowly: keep protein up and keep lifting while you lose, so more of what comes off is fat.

Coffee, chilli, green tea and cold showers do raise energy use a little for a short time. The effect is small next to the habits above, and none of them builds muscle.

Is it your thyroid?

Sometimes a slow metabolism is a medical problem. An underactive thyroid (hypothyroidism) slows the body down, and Healthdirect lists unexplained weight gain, tiredness, feeling the cold, dry skin, constipation and low mood among its symptoms. It can develop slowly over years.

A blood test for thyroid stimulating hormone (TSH) is the usual starting point. TSH tends to run higher in older age groups, so compare yours with people your age, and read it against the range on your own report. Our guide to TSH levels by age has more detail.

“Just a normal result is not necessarily what we're after for most people.”
Dr Michelle Woolhouse, Vively Medical Director

Is it your insulin?

Insulin resistance is the other common hidden cause. When cells stop responding well to insulin, the body makes more of it, and high insulin makes it easier to store fat and harder to use it. Blood glucose can stay normal for years while this happens.

A fasting insulin test picks it up early. Our optimal range is 3 to 5 mIU/L, while most lab ranges run up to about 10. HOMA-IR, calculated from fasting glucose and insulin, is optimal at 1.0 or below, and you can work yours out with our HOMA-IR calculator. To see how your markers add up to a bigger picture, try calculating your metabolic age.

How Vively can help

If you are doing the basics and your weight is still drifting up, it is worth looking underneath. The Vively Baseline is a blood test covering 70+ markers, including fasting insulin, HOMA-IR, fasting glucose, HbA1c and TSH, read against optimal ranges rather than only the lab range. A practitioner explains your results and helps you plan, and your membership includes a targeted re-test after 3 months, so you can see whether your changes are working. If you want to see how meals, sleep and movement affect your glucose day to day, our CGM program shows it in the app.

Frequently asked questions

If you have a slow metabolism, can you get a fast one?

Not dramatically, but you can raise your energy use over months. Building muscle with strength training twice a week, eating enough protein and moving more through the day all increase it. If you also have symptoms such as tiredness, feeling cold and dry skin, ask your GP to check your thyroid.

Does metabolism slow down with age?

Less than most people think. A 2021 study of energy use from infancy to age 95 found it stayed steady from about 20 to 60, once body size and muscle were accounted for, and fell after 60. Midlife weight gain is more often about losing muscle and moving less.

What foods speed up your metabolism?

No food speeds up your metabolism enough to change your weight. Coffee, chilli and green tea raise energy use slightly for a short time. Protein matters more, because it helps you keep and build muscle, which uses energy around the clock. Aim for a protein source at every meal.

How do I know if my metabolism is slow?

You cannot tell from your weight alone. Resting metabolic rate can be measured with indirect calorimetry, a breath test some clinics offer. A blood test for TSH checks your thyroid, and fasting insulin and HOMA-IR check for insulin resistance. Your GP can help decide which tests make sense.

Does dieting slow your metabolism?

Yes, to a degree. As you lose weight your body uses less energy, partly because it is smaller and partly because it adapts. In The Biggest Loser study, resting metabolism was still about 700 kcal (2,950 kJ) a day lower six years on. Slower loss with strength training and enough protein limits the drop.

Sources

1. Pontzer H et al. Daily energy expenditure through the human life course. Science 2021;373(6556):808-812.
2. Fothergill E et al. Persistent metabolic adaptation 6 years after "The Biggest Loser" competition. Obesity 2016;24(8):1612-1619.
3. Nedeltcheva AV et al. Insufficient sleep undermines dietary efforts to reduce adiposity. Ann Intern Med 2010;153(7):435-441.
4. Australian Government Department of Health. Physical activity and exercise guidelines for adults.
5. NHMRC. Nutrient Reference Values: protein.
6. Healthdirect. Hypothyroidism. Last reviewed October 2024.