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If you have a fast metabolism, you generally burn more calories at rest and while performing activities than someone with a slower metabolism does. Since your body burns more calories throughout the day, you can consume more food without gaining weight. If your metabolism is slower, you may be more likely to gain weight over time because you burn fewer calories. Your metabolic rate is affected by your body size and shape, your age, your hormone levels, and your genes.
While genetic predisposition has an enormous impact on your metabolic rate, there are changes you can make in your lifestyle to give your metabolism a boost.
Metabolism is the sum of every chemical reaction in your body. These reactions provide the energy you need to grow, reproduce, and respond to your environment. Metabolic reactions can be grouped into two categories: catabolism, processes that break down food to obtain energy and raw materials, and anabolism, processes that use energy and raw materials from food to build body tissues and organs. Together, these reactions help your body maintain homeostasis, a stable internal environment that allows you to survive and thrive.
The primary components of total daily energy expenditure include:
Between fast and slow metabolizers, the variability is 5-8% in resting metabolic rate, 20% in how much energy is expended to metabolize food, and 1-2% for differences in physical activity. Overall, the variation in metabolism is about 5-10%. This translates to about a difference of 200-300 kcal per day.1
This can be good news. While having a slower metabolism means that you burn fewer calories at rest than someone with a faster metabolism and can make it easier to gain weight, diet and exercise have a greater impact on weight gain.
Several factors contribute to slow metabolism, including genetic predisposition, body composition, and diet. The greatest of which is genetic predisposition. As researchers map the human genome and determine which combinations of genes contribute to metabolism, there may eventually be ways to increase your resting metabolic rate based on your genetics. Genes also control hormones and body composition, which also contribute to the speed of your metabolic rate.
Beyond your genetic sequence, there is another layer of genetic predisposition for weight and metabolism. This is called epigenetics. Many factors can affect your epigenetics, including the food environment your ancestors lived in and your mom’s diet and exercise practices while pregnant with you.2
Body composition, a factor you can control, also contributes to your metabolic rate. Muscle tissue is more metabolically active than fat. This means that muscle burns more calories at rest than fat. Increasing your lean muscle mass can boost your metabolism.
A decrease in muscle mass with age may partially explain why metabolic rate also decreases with age. However, a study comparing metabolic rates in older adults found that changes in body composition with age did not correlate with changes in metabolic rate. This suggests that there are changes in how body tissues use energy as we age.3
Overall, men have more lean muscle, are taller and heavier, and have higher testosterone levels than women, which may explain why men have higher metabolic rates than women. Changing your body composition by decreasing your fat mass and increasing your lean muscle mass remains the best way to increase your metabolism.
Lifestyle choices that can impact your metabolism include:
If you are concerned about your metabolism, make an appointment with your doctor for a full medical exam. Medical conditions, such as thyroid disease, can affect your metabolism. A slow metabolism and weight gain can increase your risk for type 2 diabetes and metabolic syndrome.
Many hormones affect your metabolism, but the most influential is thyroid hormone. When your thyroid hormones are low, energy uptake and metabolism slow because thyroid hormone controls energy expenditure in your body. Many of the signs associated with slow metabolism are due to low thyroid hormones.
Lifestyle changes that boost metabolism have many health benefits, including a better functioning cardiovascular system, better immune health, and stronger muscles and bones.
There are four major categories of exercise: aerobic exercise, strength training, stretching, and balance exercises, and they both have important benefits for your health. To boost your metabolism and lose weight, especially if you are older or overweight, prioritize strength-building exercises. Use gallons of milk or canned goods to strengthen your arms. Hold on to a counter and do squats to improve your leg strength. Even small amounts of daily exercise can improve your overall health and metabolism.
To boost your metabolism and to fuel muscle-building exercise, incorporate lean protein into your diet (poultry, seafood, nuts, and legumes), along with a wide variety of fruits and vegetables and healthy sources of fat. Avoid processed foods, trans fats, and highly saturated fats. To build your healthy meal plan, read “The best foods for your 40s and beyond” for ideas.
Foods that boost metabolism are ones that promote overall health, including lean sources of fat and protein, fruits, vegetables, leafy greens, green tea, coffee, and spices. Vitamin D and B-complex vitamins support a healthy metabolism, and calcium and magnesium promote healthy nerve and muscle function. If your diet is lacking, or you are at increased risk for a vitamin or mineral deficiency, read about the best foods and supplements for a healthy metabolism.
At least 7-8 hours of restful sleep is essential to reduce your risk of insulin resistance and weight gain. When you don’t get enough sleep, your cortisol levels increase, which makes it harder to exercise and lose weight. Improve your sleep quality by sleeping in a cool, dark, and quiet room; choosing comfortable bedding; limiting your intake of caffeine and alcohol before bedtime; turning off all screens at least an hour before bedtime and making time for relaxing activities.
While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.
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