Why it gets harder to build and maintain muscle mass as you age

Muscle mass is built and maintained in the same way throughout your life. However, as you age some of the processes involved in muscle creation become less effective and this can result in reduced muscle mass, strength and function. In addition, how and where body stores and metabolizes fat differs with age, which can contribute to changes in body shape.

Any body movement or exercise causes muscles to contract. This action is triggered by the brain sending a signal through the nervous system to our muscle fibers, via the release of different chemicals. This process is supported by chemicals released by mechanical sensors that respond to muscle movement. These processes cause the production of proteins, which are integrated into the muscle fibers, leading to muscle growth. 

As you age, these processes continue to occur, but the body becomes less able to respond to the stimuli and so even the same amount of exercise does not translate to the same muscle gain or maintenance that you experienced in your prime. The technical term for this reduced ability to build and maintain muscle mass is ‘anabolic resistance.’ 

What is anabolic resistance? 

Your ability to build and maintain muscle mass is determined by the balance between your body’s ability to create muscle protein, versus the rate at which your body breaks down muscle protein. Supporting muscle protein creation through nutrition and exercise will tip the balance in favour of maintaining or building muscle. However, if your body is breaking down more protein than it is creating, you will experience muscle loss, and this could lead to sarcopenia. 

Anabolic resistance describes the scenario that is seen as you age, whereby even though you continue to fuel the body with nutrition to support muscle creation and maintain an exercise regime, the body becomes less responsive to this stimulation and cannot produce the same levels of muscle protein that it did in the past. 

What causes anabolic resistance? 

Recent studies have found that older people digest and absorb around 10% less protein than younger people¹. This means that you may be eating the same amounts of protein as you did previously, but less of that protein is making its way through the digestive process into the blood stream to be used in various bodily functions, such as the creation of muscles. 

In previous blogs, we have mentioned how your lifestyle and behaviours impact the way that your genes are expressed in the body. Your DNA provides blueprint instructions to the body of how to perform different functions. The environment you create through factors such as the food you eat, your levels of physical activity, stress, and sleep, determine which genes are switched on and off. This determines how the genes instruct different bodily functions and processes. 

A recent study found that 175 protein coding genes were altered in younger people after high intensity resistance training, compared to 42 protein coding genes in older people. These genes control the regulation of muscle creation². This difference between the gene alterations in younger and older people helps us to understand the variations in the way age reduces your ability to maintain and build muscle through exercise as you age. 

What can you do to maintain and build muscle mass? 

Aging is influenced by your dietary and lifestyle behaviours and introducing healthy behaviours can positively influence muscle mass and strength. The idea is to tip the scales in the favour of muscle protein creation. 

Strength and resistance training – there are many options to choose from and this can vary from using weights to using your own body weight. Swimming, yoga, and walking are all good options, which can be enjoyed at any age. Follow this link for some simple strength training exercises that you can try at home.  

Nutrition – when it comes to protein, it is important to choose high quality protein from lean meat, or a combination of plant proteins. The recommended intake of protein varies from 0.8 to 1.8 grams per kg of your body weight, depending on your activity levels, age and whether you are looking to maintain or build muscle. Older people looking to maintain or build muscle mass should be aiming for around 80 grams of protein, based on a weight of 70kgs. It is best to split that dose across the day, including protein in each meal and snack to give the body a consistent supply.  

Sunlight – as little as 15 minutes of daily exposure to direct sunlight is sufficient for healthy vitamin D levels. This should be balanced with protecting your skin and, so it is recommended to get your sun exposure before 10am or after 3pm. 

Supplements – as your skin ages and your body becomes less capable of utilising protein from sun exposure and diet alone, supplementation is needed to support healthy levels of protein and vitamin D in the body. Supplements such as HMB and vitamin D are helpful to support healthy muscles. You can read more about HMB here. 

Suzy Walsh 

BBA (Hons)., BNat., mNMHNZ

Registered Naturopath & Medical Herbalist

References:

¹ Paulussen, K. J., et al. (2021). Anabolic resistance of muscle protein turnover comes in various shapes and sizes. Frontiers in Nutrition, 8. doi: 10.3389/fnut.2021.615849

² Rivas, D. A., et al. (2014). Diminished skeletal muscle microRNA expression with aging is associated with attenuated muscle plasticity and inhibition of IGF‐1 signaling. The FASEB Journal, 28(9), 4133-4147. doi: 10.1096/fj.14-254490