Metabolism Slowing You Down? Sluggish Metabolism Signs and Symptoms

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.

What Does It Mean to Have Slow Metabolism?

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:

  • Resting metabolic rate (60-70%)
  • Calories burned when digesting food (10-15%)
  • Calories burned from physical activity and maintaining posture (6-10%)

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.

What Causes Slow Metabolism?

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.

Foods that can slow metabolism and cause weight gain

Lifestyle choices that can impact your metabolism include:

  • Crash diets: Crash dieting and time-restricted eating can lead to weight loss, but it does not increase resting metabolic rate and may decrease it. When fifteen healthy women with obesity consumed a very low-calorie, high-protein diet and lost weight, their resting metabolic rate and thyroid hormone levels remained significantly below pre-study values.4 When 34 resistance-trained men followed an 8-hour time-restricted diet, their resting energy expenditure was unchanged.5
  • Sugary foods: Consuming foods high in fructose can decrease fat burn after eating and reduce resting energy expenditure. This can lead to weight gain if overall calories are not decreased appropriately.6 Many soft drinks and other drink manufacturers are moving away from high-fructose corn syrup, but check the labels on candy, beers, soft drinks, packaged sweets, juice drinks, condiments, and sauces.
  • Insufficient protein: Building lean muscle can help increase your resting metabolic rate. To build muscle, you need to consume protein. As you exercise, your body uses protein to build lean muscle.
  • Not enough exercise: Exercise has many benefits. To increase your metabolism and build muscle, prioritize strength-building or resistance exercises. You can increase your resting metabolic rate by an average of 5% when you make resistance training a regular part of your day.7
  • Poor sleep: Prolonged sleep deprivation or disruption can decrease your metabolic rate. Poor sleep also increases how your body uses sugar. It increases ghrelin (hunger hormone), decreases leptin (fullness hormone), and increases inflammation. These changes increase your risk of metabolic syndrome and diabetes.8,9

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.  

Thyroid gland and its impact on metabolism

Signs of a Sluggish Metabolism

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.

  • Low body temperature or getting cold easily: Burning food for energy and contracting muscles generates heat which keeps your body warm. A lower metabolic rate can cause decreased cold tolerance.
  • Difficulty losing weight: When your metabolic rate slows, and your caloric intake remains the same, you gain weight. To lose weight and change your body composition, choose a well-balanced, whole-food-based diet, ensure you get plenty of protein in your diet, and prioritize daily exercise (especially resistance training) to build muscle.
  • Consistent fatigue or low energy: Low energy and fatigue can be a sign of slow metabolism, and it can cause poor eating habits and decreased motivation for exercise, which can become a vicious cycle. Read more about what causes a lack of energy and how to increase it.
  • Slow or poor wound healing: Poor or slow wound healing may be a sign of metabolic disorders such as diabetes. Aging can also slow down the healing process because there is an increased prevalence of circulation problems, malnutrition, thinning skin, and changes in glucose metabolism with aging.  
  • Brittle skin, hair, or nails: Low thyroid hormone can cause dry, flaky skin; dry, brittle, and splitting nails; and thin, dry hair with increased hair loss. Thyroid disease is more common with age. Read tips for better skin as you age to learn more about improving your skin and turning back the signs of aging.

How To Boost Your Metabolism

Lifestyle changes that boost metabolism have many health benefits, including a better functioning cardiovascular system, better immune health, and stronger muscles and bones.

Exercise

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.

Healthy foods on a cutting board

Eat Healthily

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.

Supplement Your Nutrition

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.  

Get Better Sleep

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.

Disclaimer

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. 

References

1. Donahoo WT, Levine JA, Melanson EL. Variability in energy expenditure and its components. Curr Opin Clin Nutr Metab Care. Nov 2004;7(6):599-605. doi:10.1097/00075197-200411000-00003

2. Keating ST, El-Osta A. Epigenetics and Metabolism. Circulation Research. 2015;116(4):715-736. doi:doi:10.1161/CIRCRESAHA.116.303936

3. Fukagawa NK, Bandini LG, Young JB. Effect of age on body composition and resting metabolic rate. American Journal of Physiology-Endocrinology and Metabolism. 1990;259(2):E233-E238. doi:10.1152/ajpendo.1990.259.2.E233

4. Barrows K, Snook JT. Effect of a high-protein, very-low-calorie diet on resting metabolism, thyroid hormones, and energy expenditure of obese middle-aged women. Am J Clin Nutr. Feb 1987;45(2):391-8. doi:10.1093/ajcn/45.2.391

5. Moro T, Tinsley G, Bianco A, et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. Oct 13 2016;14(1):290. doi:10.1186/s12967-016-1044-0

6. Cox CL, Stanhope KL, Schwarz JM, et al. Consumption of fructose-sweetened beverages for 10 weeks reduces net fat oxidation and energy expenditure in overweight/obese men and women. Eur J Clin Nutr. Feb 2012;66(2):201-8. doi:10.1038/ejcn.2011.159

7. Aristizabal JC, Freidenreich DJ, Volk BM, et al. Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map. European Journal of Clinical Nutrition. 2015/07/01 2015;69(7):831-836. doi:10.1038/ejcn.2014.216

8. Buxton OM, Cain SW, O’Connor SP, et al. Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Sci Transl Med. Apr 11 2012;4(129):129ra43. doi:10.1126/scitranslmed.3003200

9. Nedeltcheva AV, Scheer FA. Metabolic effects of sleep disruption, links to obesity and diabetes. Curr Opin Endocrinol Diabetes Obes. Aug 2014;21(4):293-8. doi:10.1097/med.0000000000000082

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Published: Jan 5, 2023

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