May 11, 2021

How to speed up your metabolism with training

Learn how you can reverse the metabolic slowdown through science.

You have undoubtedly heard of the term Metabolism. Although most people don’t know what it means, it is often considered the culprit for failed weight loss attempts or general inability to achieve a fitness goal.  

Metabolism comprises all biological processes that convert fuel from nutrients (i.e., fats, carbs, protein) into the energy our body needs to survive (i.e., calories). In simple terms, it’s the process through which we burn calories and is the most vital biological process. It provides a constant supply of the energy needed to power your body movements and all functions keeping you alive such as breathing, blood circulation, cell growth, reparation, etc. Metabolism differs significantly from one person to another. Factors that affect it and cause it to be different from the person sitting next to you include age, genetics, exercise, nutrition, and medication.

Having a high metabolism means your body burns more calories than predicted for the average person with the same age, weight, height, and gender as you. Conversely, having a slow metabolism means you are burning fewer calories than predicted. Besides burning more calories, however, having a high metabolism is associated with more pronounced cellular and muscle tissue reparation, and other healing processes vital to recovery after training. Consequently, making sure your metabolism stays high is of vital importance to your long-term health, given that weight gain constitutes the number one driver behind the most deadly and costly killers such as heart disease, diabetes, etc. Moreover, given that an elevated metabolism also results in higher recovery capacity, it’s also crucial for avoiding injuries. 

What can cause my metabolism to slow down?

Aging, nutrition, and training can all lead to a metabolic decline. Here’s how that can happen:

1. Reduction in muscle mass due to caloric restriction. As discussed in our blog post “Why diets fail” caloric restriction, one of the most substantial factors leading to metabolic slowdown byways of reducing muscle mass. Restricting calorie intake and causing a caloric deficit means your body needs to expend some of its energy reserves to cover the energy gap between calorie intake and output. Your body’s primary energy reserves are fat, and muscle tissue, so inevitably a calorie deficit will lead to some loss in muscle mass.

2. Hormonal perturbations that will cause your body to be more economical in burning calories by burning fewer calories than expected for your age, gender and weight. The reduction in calorie burn is predominantly due to an increase in skeletal muscle efficiency. In simple terms, your muscles can now do more movement, such as going up the stairs, while using less energy (i.e., calories) [1].

3. Aging will cause your metabolism to decline since the older we get the harder it is to maintain muscle mass and the less metabolism-boosting hormones (e.g. growth hormone) we secrete.

4. Training can be a powerful tool for increasing your metabolism but excessive doses will have the opposite effect. In the case of athletes, overtraining has also been shown to elicit hormonal changes that will reduce metabolic processes [4]. In this case, metabolic decline poses a problem due to the associated reduction in healing processes vital to recovery after training. However, long exercise sessions have been shown to halt the secretion of growth hormone, a hormone vital for boosting your metabolism.

How can exercise help my metabolism increase?

When considering the factors affecting your metabolism, exercise is undoubtedly the most potent while also being one in your complete control. In simple terms, by effectively optimizing your exercise routine, you can increase your metabolism or reverse a downwards trend. Here are some powerful ways training can help you:

1. Resistance training can increase your muscle mass even under a state of caloric deficit. Muscle burns three times more calories than fat at rest and up to 20 times when it’s working [2]. Therefore, maintain or increasing muscle mass can lead to significantly higher calorie burn throughout the day. The effects of resistance training in boosting your metabolism maximize when your program focuses on large muscle groups such as your leg and back muscles. These muscle groups participate in almost every daily activity and movement, so increasing their size will have the most significant increase in your total daily calorie burn.

2. Resistance training can help reverse the hormonal effects of caloric restriction that cause your muscles to become more economical and burn fewer calories when being used. In simple terms, through resistance training, every pound of muscle mass will burn more calories than before when used, making it easier to maintain or lose weight without making enormous sacrifices in your diet. It’s important to note that such effects have been recorded in both obese and non-obese individuals, indicating that resistance training can lead to a similar increase in muscle calorie consumption regardless of weight loss history [3].

3. In case you are a professional or recreational athlete make sure you are keeping your training volume in check. The threshold for overtraining will vary substantially based on your fitness level and current metabolic state so make sure to conduct a metabolic test to accurately estimate your maximum allowable weekly training volume [4].

4. In case your training for life and want to get the most out of your weekly workout sessions make sure you maintain your exercise intensity at the right level and the right duration. Exercise for too long or going above your maximum allowable intensity in either resistance or cardio-based training will mitigate the secretion of growth hormone and the uptick on your metabolism your training may have [5]. To ensure you are working at the right intensity and duration make sure you identify your training zones through an active metabolic test.


A metabolic slowdown can pose a severe obstacle in achieving your dream physique and staying healthy long-term. Understanding if your metabolism has slowed down or whether your current fitness and nutrition are causing it to slow down is perhaps the most important thing to track. The PNOĒ metabolic analyzer has helped thousands measure their metabolism, act early and avoid the detrimental implications of a metabolic slowdown. Weight loss and, by implication calorie restriction, is necessary for many who need to drop a few pounds. However, by using exercise appropriately, one can make the few months a diet lasts a once and for all process. 


1. Adaptive thermogenesis in humans., Int J Obes (Lond). 2010 October; 34(0 1): S47–S55. doi:10.1038/ijo.2010.184.

2. Resting Energy Expenditure: Systematic Organization and Critique of Prediction Methods., OBESITY RESEARCH Vol. 9 No. 5 May 2001

3. Resistance Training Reduces Skeletal Muscle Work Efficiency in Weight-reduced and Non-weight-reduced Subjects., Obesity (Silver Spring). 2018 October ; 26(10): 1576–1583. doi:10.1002/oby.22274.

4. Cadegiani, F. A., da Silva, P., Abrao, T., & Kater, C. E. (2020). Diagnosis of Overtraining Syndrome: Results of the Endocrine and Metabolic Responses on Overtraining Syndrome Study: EROS-DIAGNOSIS. Journal of sports medicine (Hindawi Publishing Corporation), 2020, 3937819.

5. The impact of sex and exercise duration on growth hormone secretion., Journal of Applie Physioly., 2006;

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