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Why Your Metabolism Is Slow & How To Fix It (Backed by Science)

As far as weight loss is concerned there are hundreds, if not thousands, of different variables, all of which affect your ability to lose weight and influence how easy and efficient the process is.

One of the major determinants of your ability to lose weight and how easily it occurs is your metabolic rate. Your metabolic rate is comprised of all energy expenditure that your body experiences from any activity, like eating and even just breathing and maintaining posture.

Unfortunately, there are many different factors that may be causing a slowdown of your metabolism. These often result in increased difficulty if you are trying to lose a significant amount of weight in a reasonable amount of time.

In this article, I’ll discuss some of the most common reasons why your metabolic rate is functioning at subpar rates and ways to improve it for easier and more efficient weight loss.

Age-related Estrogen Decline 

One of the biggest culprits behind your metabolic slowdown is certainly one that is almost entirely out of your control, i.e. age.

With age, comes a decrease in the estrogen produced by your ovaries, which, as you probably know, is one of the major drivers of the menopause.

Unfortunately, estrogen is also tightly linked with the ability of your thyroid to function properly (1).

The thyroid is a gland that produces the thyroid hormones, such as T3 and T4. When released into circulation, these hormones act on many different tissues in the body to affect metabolic rate.

In young, healthy individuals, these hormones act on cells to increase metabolism by regulating how, (and how quickly), different macronutrients such as protein, carbohydrate and fat are metabolized. Further, having high thyroid hormone output can increase metabolism and lead to increased fat metabolism and thus, weight loss.

While many at this time in their life will consider hormone replacement therapy (HRT), it isn’t always appropriate or even necessary as a first line of defense. Before resorting to HRT, first try to begin moderating your food intake and then incorporating intense exercise.

When age-related metabolic slowdown occurs the food you eat will have a larger impact on your weight. For this reason, you’ll need to focus primarily on increasing your protein and vegetable intake to ensure that you’re getting nutrients, but also not eating too much which would result in weight gain.

Additionally, using supplements containing ingredients like Tyrosine, Ashwagandha and iodine, such as CapLabs Thyroid & Metabolism support, may help encourage your metabolism to improve a bit for more efficient weight loss (2, 3, 4).

metabolic slowdown

You’re Dieting Too Much 

One of the biggest issues I’ve observed, after working with hundreds of clients, is that many people just diet far too hard, for way too long. As a result, metabolism adapts and weight loss feels impossible.

Under normal conditions, you have a certain metabolic rate that encompasses energy needs of the body. This includes resting metabolic rate, the thermic effect of food and even NEAT (non-exercise activity thermogenesis), or energy expended during things like walking, cleaning, talking and even breathing.

When you first start dieting, this metabolic rate is maintained for a given period of time. That’s why if you restrict calories, you lose weight since you’re burning more calories than you are consuming.

Unfortunately, your metabolism doesn’t care about reducing cellulite or slimming your tummy; it cares about keeping you alive.

When restricting calories for an extended period of time, your metabolism adapts by reducing the amount of calories that the body requires for any given activity. In essence, dieting makes the body more efficient at operating on less, requiring less energy to carry out daily functions.

In order to avoid metabolic slowdown, your best line of defense is to use calorie cycling and re-feeds.

In essence calorie cycling simply means taking breaks from restricting calories so that you can avoid the metabolic adaptation, and its slowing down, to match the reduced amount of calories you are consuming.

Further, calorie cycling in essence incorporates the use of what are known as refeeds.

To use calorie cycling, after restricting calories for two to three weeks, you’ll return to your normal, higher calorie intake for a period of a few days to a week. During this time, you’ll consume more calories, allowing for your metabolism to have a break from the reduction of calories.

Upon completing this “refeed” period of time, you can then return to the lower intake amount and continue losing weight.

You Restrict Carbs Too Much 

Another potential culprit behind your metabolic slowdown is the fact that you’re restricting carbohydrates far too much.

In the world of mainstream fitness, there are so many conflicting arguments revolving around carbohydrate consumption. Really, on their own, carbohydrates are not the cause of weight gain. The only way they become an issue is when their consumption leads to an overall increase in calorie consumption.

Unfortunately again, for those of us whom have restricted calories significantly, having too low a carb consumption for long periods of time may actually reduce the output of thyroid hormones (5).

In one specific study, researchers observed women who restricted calories, having one group consume higher amounts of carbs with the other using a very low carb approach.

At the end of the study, researchers revealed that compared to the group using high carbs, despite having equal calories, the low carb group had significantly lower output of the thyroid hormone known as T3. As you know, this can significantly impact your metabolism.

To combat this, I suggest using a carb cycling approach, rather than simply always restricting carbs. Doing so will allow you to eat carbs when you need them according to exercise while limiting them on days when you do less, e.g. on a rest day.

To use this method, simply increase your carb consumption of days when you train hard and reduce carb intake on days where exercise is light or on a rest day.

By using this method, you’ll allow for regular fluctuations of carb intake, thus avoiding metabolic slowdown, while still moderating your carb consumption based on your daily activity level.

metabolic slowdown

Why Your Metabolism Is Sluggish

Certainly some of the reasons why your metabolism is sluggish may be out of your control. Issues like age-related estrogen decline and subsequent reduced thyroid function are obviously not down to lifestyle choice.

However, you may be your own worst enemy if you’ve been dieting constantly for years, all while completely restricting your carb intake. Fortunately, there are some fairly easy solutions when it comes to adjusting your diet for a more optimized metabolism.

By using these methods described above or following my results guaranteed transformation plans, you can improve your metabolism and start losing fat at a rapid rate.

Learn more about my Metabolic Advantage Diet or my 90 Day Bikini plan which both use advanced techniques to boost your metabolism and help you burn more fat.


  1. Lizcano, F., & Guzmán, G. (2014). Estrogen deficiency and the origin of obesity during menopause. BioMed research international, 2014.
  2. Fernstrom, J. D., & Fernstrom, M. H. (2007). Tyrosine, phenylalanine, and catecholamine synthesis and function in the brain. The Journal of nutrition, 137(6), 1539S-1547S.
  3. Zimmermann, M. B., & Köhrle, J. (2002). The impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to public health. Thyroid, 12(10), 867-878.
  4. Wankhede, S., Langade, D., Joshi, K., Sinha, S. R., & Bhattacharyya, S. (2015). Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. Journal of the International Society of Sports Nutrition, 12(1), 43.
  5. Mathieson, R. A., Walberg, J. L., Gwazdauskas, F. C., Hinkle, D. E., & Gregg, J. M. (1986). The effect of varying carbohydrate content of a very-low-caloric diet on resting metabolic rate and thyroid hormones. Metabolism, 35(5), 394-398.


About the author

Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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