Can I boost my metabolism?

Metabolism refers to the chemical processes that occur within your body to maintain life, including converting food into energy. This involves 2 key components.

Basal Metabolic Rate (BMR)

The number of calories your body needs to keep you alive at rest before any activity is added, like breathing, circulation, and basic organ function.

Total Energy Expenditure (TDEE)

The total number of calories you burn in a day, including your BMR plus movement, exercise, digestion, and everyday activity.

Basal metabolic rate (BMR)

BMR is the number of calories your body burns at rest to maintain essential functions, such as breathing, circulation, and cell repair. BMR accounts for approximately 60 to 80% of daily calorie expenditure. It’s influenced by factors such as:

• age – as we age, muscle mass decreases, slowing BMR
• sex and body size – larger bodies generally have higher BMR
• body composition – more muscle mass means a higher BMR, as muscle tissue burns more calories at rest

Although BMR can be slightly influenced by building muscle through strength training or small hormonal changes, it cannot be dramatically boosted.

Activity-related energy expenditure

Physical activity – all energy burned through movement, known as non-exercise activity thermogenesis (NEAT), including structured exercise, walking, household chores, and commuting – significantly impacts metabolism.

The total calories burned depend on the frequency, intensity, and duration of activity, meaning that consistent movement can meaningfully increase the energy you use daily.

Small lifestyle changes, such as taking the stairs, standing more, or walking instead of driving, can add up over time, providing achievable ways to consume more energy and lose weight.

Thermic effect of food

The thermic effect of food (TEF) is the energy required to digest, absorb, and store nutrients, typically accounting for about 8 to 15% of total daily energy use. TEF varies by macronutrient, with protein generally requiring the most energy to process, followed by carbohydrates and fat.

Lifestyle changes, such as dietary changes or taking part in exercise, can modestly influence metabolism over time.

Diet and eating habits

Eating more protein increases the energy required to digest, absorb, and store nutrients, which slightly raises calorie burn during digestion. Protein also supports muscle maintenance, which is important for preserving metabolism during weight loss.

Staying well-hydrated and spreading meals throughout the day may have a modest impact on energy expenditure and regulating your appetite. Some studies suggest potential benefits of meal timing and water intake, but the evidence is limited and mixed.

Physical activity

Building muscle through resistance or strength training helps maintain the energy you consume while resting, because muscle tissue uses more energy than fat, even at rest. This matters during weight loss, as it helps limit the drop in metabolism that often happens when you lose weight.

Both high-intensity interval training (HIIT) and regular moderate-intensity exercise can increase the total daily energy you consume, meaning you burn more calories across the day. This supports metabolic health and weight management, even though the effect on metabolism itself is gradual rather than dramatic.

Daily movement (“NEAT”)

NEAT, refers to all calories burned through daily movements outside of formal exercise, including walking, fidgeting, household chores, and commuting.

For many people, NEAT can account for hundreds of calories burned per day, and in some cases, this may even exceed the calories burned during structured exercise.

Sleep and stress

Lack of sleep and stress can negatively affect energy balance and metabolism. Poor sleep disrupts hormones that regulate appetite, like ghrelin, increasing hunger and calorie intake. Sleep restriction can also slightly lower the amount of energy your body uses at rest.

Ongoing stress can raise cortisol levels, which is linked to increased fat storage around the abdomen. It can also make it harder to stick to healthy eating habits or stay active, which can affect your overall energy balance over time.

There are many products marketed as metabolism boosters, but most lack scientific backing and have minimal, short-term effects. The UK regulatory environment for diet supplements is different from medicines, meaning metabolism-boosting claims do not require clinical evidence before these products are marketed.

Regulation and evidence

In the UK, dietary supplements are not regulated to the same standards as prescription medications and do not have to prove effectiveness or safety before being sold. The NHS and NICE (National Institute for Health and Care Excellence) do not list metabolism boosters as recommended treatments for weight loss.

Weight loss should focus on diet, physical activity, and healthy lifestyle habits, with the understanding that supplements cannot replace these fundamentals and may carry risks or interact with medications.

What ingredients are commonly claimed to increase metabolism?

Caffeine and green tea extract

Some studies suggest that green tea extract, which contains caffeine and catechin polyphenols, can slightly increase energy expenditure and fat oxidation over 24 hours. However, the effect is small and unlikely to lead to meaningful weight loss on its own.

Carnitine, capsaicin, and other herbal ingredients

Evidence for these ingredients is limited and inconsistent, with no significant changes in energy expenditure seen in human studies.

Overall, these supplements can cause side effects or interact with medications, and there is no strong evidence that they lead to safe or sustained weight loss.

Understanding how metabolism works can help guide realistic and healthy weight loss strategies, rather than chasing quick fixes or supplements that lack reliable evidence. By focusing on factors that genuinely affect energy balance, you can achieve sustainable fat loss while supporting your overall health.

Create a sustainable calorie deficit

Weight loss requires an energy deficit – consuming fewer calories than your body expends. However, extreme calorie restriction can backfire: very low-calorie diets may lower metabolic rate, promote muscle loss, and are often difficult to maintain long-term.

A more effective approach is to make gradual, steady changes to eating habits, creating a moderate deficit that promotes fat loss while preserving lean muscle mass. This makes weight loss more sustainable and helps prevent the metabolic slowdown often seen with extreme diets.

Combine metabolic support with diet and activity

Lean muscle tissue uses more energy than fat, even when you’re resting. Strength training helps preserve or slightly increase resting energy expenditure during weight loss, while getting enough protein supports muscle maintenance and causes a small increase in the energy used to digest food.

Regular physical activity also plays an important role. This includes both planned exercise and NEAT activity. Together, these contribute to how many calories you burn across the day.

Overall, a balanced diet, regular movement, and maintaining muscle mass are the most reliable ways to support metabolism and achieve sustainable weight loss. These approaches help maintain energy balance during weight loss, but they work within normal biological limits and do not dramatically increase your metabolic rate.

Prescription weight loss medications, such as Wegovy (semaglutide) and Mounjaro (tirzepatide), mainly work by reducing appetite, making it easier to create a calorie deficit.

It's important to note that these medications do not directly increase metabolism. To support metabolic health during treatment, it’s still important to maintain lean muscle through strength training, while also consuming enough protein.