How to Increase Metabolism: UK Guide

How to increase metabolism is a question many people ask, whether they are struggling with weight management, low energy, or simply want to understand how their body uses fuel. Metabolism encompasses every chemical process that converts food and drink into energy, and while it is influenced by factors such as age, muscle mass, hormones, and genetics, there are evidence-based strategies that can support it. This article explains what causes metabolic rate to slow, how exercise, diet, sleep, and stress each play a role, and when symptoms warrant a conversation with your GP.

What is metabolism and why does it slow down?

Metabolism slows primarily due to age-related muscle loss (sarcopenia), hormonal changes, and prolonged calorie restriction. Clinically significant reductions are usually linked to conditions such as hypothyroidism rather than lifestyle alone.

Metabolism is the sum of all chemical processes your body uses to convert food and drink into energy, and it naturally slows with age, changes in body composition, and certain health conditions. The rate at which your body burns calories at rest is called the basal metabolic rate (BMR), which typically accounts for the largest share of daily energy expenditure in most adults, though this varies with activity level and body composition.^[3] Factors such as muscle mass, thyroid hormone levels, and genetics all influence how efficiently this process runs.

Several reasons explain why metabolism tends to decline over time. From around the age of 30, adults gradually lose muscle mass, a process known as sarcopenia, and because muscle tissue burns more calories than fat tissue even at rest, this shift reduces overall energy expenditure.^[4][5] Hormonal changes, particularly those associated with the menopause or reduced thyroid output, can further dampen metabolic rate. Prolonged calorie restriction, sometimes called "crash dieting", can also cause the body to adapt by lowering its resting energy use, making sustained weight management more challenging.

Certain medicines can also affect weight and metabolism. These include some antipsychotics, antidepressants, corticosteroids, and medicines used to treat diabetes such as insulin or sulfonylureas. If you think a prescribed medicine may be affecting your weight, speak to your GP or prescriber before making any changes.

It is worth noting that the term "slow metabolism" is often used loosely. Clinically meaningful reductions in metabolic rate are usually linked to identifiable causes, such as hypothyroidism or Cushing's syndrome, rather than simply lifestyle habits. Understanding the distinction between normal age-related changes and a medically significant metabolic condition is important before pursuing any intervention.

Does exercise really speed up your metabolism?

Yes. Resistance training raises BMR by increasing lean muscle mass, while aerobic activity and incidental movement (NEAT) contribute to daily energy expenditure. UK guidelines recommend 150 minutes of moderate activity weekly plus two muscle-strengthening sessions.

Regular physical activity does increase metabolic rate, both during exercise and for a period afterwards, and building muscle through resistance training produces the most sustained long-term effect. When you exercise, your muscles demand more energy, raising your metabolic rate above its resting level. This elevated state can persist for some hours after a session, a phenomenon sometimes called excess post-exercise oxygen consumption (EPOC), though the magnitude is modest and varies with exercise intensity and individual fitness.

Resistance training, such as weight lifting or bodyweight exercises, is particularly effective because it increases lean muscle mass. Since muscle is metabolically more active than fat, a greater proportion of muscle in your body composition raises your BMR over time. UK Chief Medical Officers' guidelines recommend that adults aim for at least 150 minutes of moderate-intensity aerobic activity per week, or 75 minutes of vigorous-intensity activity, alongside muscle-strengthening activities on two or more days.^[1][2] Both components contribute to metabolic health.

High-intensity interval training (HIIT) has attracted attention for its potential to boost post-exercise calorie burning in a shorter time than steady-state cardio, though the overall evidence suggests that the total calorie deficit and consistency of exercise matter more than the specific format chosen. Non-exercise activity thermogenesis (NEAT), which covers all movement outside formal exercise such as walking, standing, and fidgeting, also contributes meaningfully to daily energy expenditure. Incorporating more incidental movement throughout the day, such as taking the stairs or walking during lunch breaks, can make a practical difference over time.

If you have a long-term health condition, a disability, or are pregnant, speak to your GP or a healthcare professional before starting or significantly changing an exercise programme, as activity recommendations may need to be tailored to your circumstances.

How does what you eat affect your metabolic rate?

Protein has the highest thermic effect of food, making adequate protein intake the most evidence-supported dietary strategy for supporting metabolic rate and preserving muscle mass during weight loss.

Dietary choices influence metabolic rate through several mechanisms, including the thermic effect of food, macronutrient composition, and meal timing, though no single food or supplement dramatically transforms metabolism on its own. The thermic effect of food (TEF) refers to the energy your body expends digesting, absorbing, and processing nutrients. Protein has the highest TEF of the three macronutrients, meaning a meaningful proportion of its calorie content is used in the process of metabolising it, compared with considerably less for carbohydrates and very little for fats. Exact percentage figures vary across studies and should be interpreted as approximate ranges rather than fixed values.

Eating adequate protein is therefore one of the most evidence-supported dietary strategies for supporting metabolic rate. Protein also helps preserve lean muscle mass during weight loss, which protects BMR from declining. Good sources include lean meat, fish, eggs, dairy, legumes, and tofu. Fibre-rich foods, including vegetables, wholegrains, and pulses, also require more digestive effort and contribute to satiety, helping to regulate overall energy intake.

Some foods and drinks, such as green tea, caffeine, and chilli peppers, have been studied for modest, short-term thermogenic effects, but the evidence for meaningful or lasting metabolic benefits in humans is limited and should not be overstated. Severely restricting calories, by contrast, can suppress metabolic rate as the body conserves energy, which is one reason very low-calorie diets are not recommended without medical supervision. A balanced, varied diet aligned with the NHS Eatwell Guide principles remains the most practical foundation for supporting healthy metabolic function.

Can sleep and stress levels change how fast you burn calories?

Poor sleep disrupts hunger hormones and reduces insulin sensitivity, while chronic stress elevates cortisol, promoting fat storage and muscle breakdown, both of which lower resting metabolic rate.

Poor sleep and chronic stress can both negatively affect metabolic rate and body composition, primarily through their influence on hormones that regulate appetite, fat storage, and energy use. Sleep deprivation disrupts the balance of ghrelin and leptin, the hormones that signal hunger and fullness respectively, leading to increased appetite and a preference for calorie-dense foods. Research also suggests that insufficient sleep reduces insulin sensitivity, which can impair the body's ability to regulate blood glucose efficiently.

Chronic psychological stress raises levels of cortisol, a hormone produced by the adrenal glands. Persistently elevated cortisol promotes fat storage, particularly around the abdomen, and can contribute to muscle breakdown over time. This shift in body composition, favouring fat over muscle, has a downstream effect on resting metabolic rate. Stress-related behaviours, such as disrupted eating patterns, reduced physical activity, and poor sleep, compound these physiological effects.

The NHS advises that most adults need between 6 and 9 hours of sleep per night, though individual needs vary.^[12][13] Practical strategies to support sleep quality include maintaining a consistent sleep schedule, limiting screen exposure before bed, and keeping the bedroom cool and dark. For stress management, evidence-based approaches include regular physical activity, mindfulness-based techniques, and talking therapies such as cognitive behavioural therapy (CBT), which is available through NHS Talking Therapies.^[14][15] Addressing sleep and stress is not a peripheral concern in metabolic health; it is a central one, and improvements in these areas can support the effectiveness of dietary and exercise changes.

When should you speak to a GP about a slow metabolism?

See a GP if you have unexplained weight gain, persistent fatigue, feeling cold, hair thinning, or constipation, as these may indicate hypothyroidism or another treatable condition requiring blood tests.

You should speak to a GP about a slow metabolism if you are experiencing unexplained weight gain, persistent fatigue, feeling cold all the time, dry skin, hair thinning, or constipation, as these can be signs of an underactive thyroid (hypothyroidism) or another treatable medical condition.^[16] Conversely, symptoms such as unintentional weight loss, palpitations, heat intolerance, or tremor may suggest an overactive thyroid (hyperthyroidism) and also warrant prompt assessment. Symptoms such as increased thirst, frequent urination, or unexplained tiredness may indicate diabetes and should be discussed with a GP. These symptoms warrant investigation rather than self-management, and a GP can arrange a simple blood test to assess thyroid function, blood glucose, and other relevant markers.

Polycystic ovary syndrome (PCOS) is another condition that can affect weight and metabolism. Common features that merit GP assessment include irregular or absent periods, excess hair growth, and acne, alongside difficulty managing weight.^[17] Early identification of conditions such as hypothyroidism, PCOS, or insulin resistance allows for appropriate treatment that can meaningfully improve metabolic health.

It is also worth seeking a GP review if lifestyle changes, including improved diet, regular exercise, better sleep, and stress management, have been consistently applied for several months without any improvement in weight or energy levels. In some cases, a referral to a dietitian, endocrinologist, or specialist weight management service may be appropriate. NICE guidance supports structured weight management programmes for eligible individuals, and your GP can advise on what is available locally through your Integrated Care Board (ICB).^[18]

If you are taking a prescribed medicine that you think may be affecting your weight or metabolism, speak to your GP or prescriber before making any changes to your treatment.

For those where a medical assessment confirms that weight management support is appropriate, a range of options may be considered, including lifestyle programmes and, where clinically indicated, pharmacological treatment. Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online weight-management consultations, with prescriber review and pharmacist support, as one avenue through which clinically appropriate options may be explored.

If you experience sudden, severe symptoms such as chest pain, difficulty breathing, or collapse, call 999 immediately. For urgent but non-emergency concerns, NHS 111 can provide guidance. Suspected side effects from any prescribed medicine can be reported to the MHRA via the Yellow Card scheme at yellowcard.^[19]mhra.gov.uk.

Scientific References

1. UK Chief Medical Officers' physical activity guidelines.
2. Physical activity guidelines for adults aged 19 to 64.
3. Skeletal muscle metabolism is a major determinant of resting metabolic rate.
4. The link between Mitochondria and Sarcopenia.
5. Adiposity, muscle mass, and muscle strength in relation to functional decline in older persons.
6. The Energy Content and Composition of Meals Consumed after an Overnight Fast and Their Effects on Diet Induced Thermogenesis: A Systematic Review, Meta-Analyses and Meta-Regressions.
7. International Society of Sports Nutrition position stand: diets and body composition.
8. A single night of sleep deprivation increases ghrelin levels.
9. Elevated ghrelin predicts food intake during experimental sleep restriction.
10. Sleep curtailment is accompanied by increased intake of calories from snacks.
11. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite.
12. Sleep problems – Every Mind Matters.
13. Insomnia.
14. Cognitive behavioural therapy (CBT).
15. Find NHS talking therapies for anxiety and depression.
16. Thyroid disease: assessment and management (NG145).
17. Polyendocrine Metabolic Ovarian Syndrome (PMOS) – guideline in development (GID-NG10436).
18. Overweight and obesity management (NG246).
19. The Yellow Card scheme: guidance for healthcare professionals, patients and the public.
20. [Psychotropic drugs and diabetes].

Frequently Asked Questions