Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Struggling to shed those extra kilos despite eating well and staying active? It might not just be your diet or exercise routine – your metabolism could be at play.
Your metabolism is responsible for converting food into energy, so when it slows down, your body holds onto calories instead of burning them. According to studies, factors like ageing, hormonal changes, and lifestyle habits can significantly reduce your metabolic rate.
Let’s explore the causes, signs, and ways to give your metabolism a much-needed boost.
Metabolism doesn’t slow down for no reason. There are often clear factors behind it. Figuring out what’s causing the change means you can take charge and support your body the right way.
As we age, muscle mass naturally decreases, and fat mass tends to increase. This slows down your basal metabolic rate (BMR), which is the energy your body uses at rest. Research shows that BMR can decline by 1–2% per decade after age 20, making weight management more challenging over time.
Spending too much time sitting or avoiding physical activity can lower your metabolism. Muscle is more metabolically active than fat, so when activity levels drop, your muscle mass decreases, slowing calorie burn. Even light exercises, like walking, can help counteract this.
Hypothyroidism, or an underactive thyroid, is a common cause of slow metabolism. When your thyroid doesn’t produce enough hormones, your body processes slow down. Symptoms like fatigue, weight gain, and sensitivity to cold often accompany this condition.
Eating too few calories or relying on processed foods can mess with your metabolism. When your body senses it’s not getting enough nutrients, it goes into conservation mode, slowing your calorie burn to preserve energy. A diet lacking in protein, in particular, can reduce muscle maintenance and metabolic rate.
Fluctuations in hormones like insulin, cortisol, and oestrogen can significantly impact metabolism. For example, high cortisol levels from chronic stress can lead to fat storage, particularly around the belly, while low testosterone levels in men can reduce muscle mass.
A sluggish metabolism doesn’t hide for long. It often shows up in ways that affect your energy, appearance, and overall health.
One of the most noticeable signs of slow metabolism is unexplained weight gain. If you’re eating the same but gaining weight, your body may not be burning calories efficiently. This happens because a slower metabolism stores more calories as fat.
Feeling constantly tired, even after a good night’s sleep, can signal a slow metabolism. Your body struggles to convert food into energy, leaving you feeling drained.
A slower metabolism affects circulation and nutrient delivery to your skin, leading to dryness and flakiness. Without enough energy, your skin may struggle to maintain its natural moisture barrier.
Do you feel chilly while everyone else is comfortable? A slow metabolism generates less body heat, making you more sensitive to cold environments.
Slower digestion is a common side effect of reduced metabolic activity. When your metabolism slows, your gut processes food more sluggishly, often leading to constipation.
A reduced metabolism can lower your resting heart rate, as your body tries to conserve energy. While this might sound healthy, an unusually slow heart rate could indicate an underlying issue.
Struggling to shed kilos despite dieting and exercising? A slow metabolism burns fewer calories, making weight loss efforts feel like an uphill battle.
If your metabolism feels sluggish, there’s good news: small lifestyle changes can give it a boost.
Regular exercise, particularly strength training, helps build muscle, which increases your resting metabolic rate. Even incorporating activities like walking or yoga can make a difference over time.
Protein has a higher thermic effect than carbs or fats, meaning your body uses more energy to digest it. Including lean meats, eggs, and legumes in your meals can help keep your metabolism active.
Staying hydrated is essential for metabolic processes. In fact, a study suggests that drinking about 500 ml of water can increase your metabolism by roughly 30%—and it kicks in within 10 to 40 minutes.
Poor sleep disrupts the hormones that regulate appetite and metabolism. Aim for 7–8 hours of quality sleep each night to support your body’s natural rhythms.
Chronic stress raises cortisol levels, which can slow metabolism and promote fat storage. Incorporate relaxation techniques like meditation, deep breathing, or hobbies to keep stress in check.
High-intensity interval training (HIIT) can give your metabolism a significant boost by combining short bursts of intense exercise with recovery periods. This type of workout keeps your body burning calories long after the session ends.
Understanding the signs and causes of a slow metabolism can help you take control. With a balanced diet, regular exercise, and healthy habits, it’s possible to reignite your body’s energy engine. If you suspect an underlying issue, consult a healthcare professional for personalised advice.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.