Understanding Sarcopenic Obesity

As we age, our metabolic rate slows down, and we tend to pack on unwanted pounds while losing muscle mass. To combat this, we often resort to a variety of lifestyle changes, such as regular exercise, healthier food choices, and meditation. However, the results are often mixed. While we may experience a reduction in body fat, we also tend to feel tired and lose muscle strength. What causes this problem, and can we do anything about it?

In this blog, we will explore the fundamentals of sarcopenic obesity (SO), a condition characterized by the simultaneous loss of muscle mass and weight gain and the risks associated with it.

What is Sarcopenic Obesity (SO)?

As we hit our 30s, muscle mass starts to decline, leading to a drop in strength and physical abilities. When this happens, we’re more likely to become less active, which can lead to weight gain. The combination of losing muscle and gaining fat can result in a condition called sarcopenic obesity, or SO.

SO is when you have both sarcopenia (loss of muscle mass and strength) and obesity (too much body fat) at the same time. It’s pretty common in older adults, affecting about 18% of older women and 40% of older men. Now, the burning question is… what causes SO?

Diving into the basis of SO

Interestingly, SO is likely influenced by several factors, especially as we age. Some things that might kick off SO include changes in how our muscles build and break down proteins, issues with energy production in our cells’ mitochondria, increased inflammation, nerve signal problems, changes in nutrition and hormones, and trouble with muscle stem cells. Let’s unpack some of the known factors in depth:

• Protein Turnover: Our muscles are constantly making and breaking down proteins, like a farm where old crops are cleared away and new ones are planted. As we age, our muscles tend to produce fewer new proteins, and at the same time, they break down more of the old ones. This imbalance means we’re losing muscle mass, which can lead to SO.

When we eat a protein-rich meal, it kick-starts muscle protein synthesis thanks to essential amino acids. These are the building blocks of proteins, and while our bodies can make some of them, others have to come from our diet. One amino acid, leucine, is especially good at boosting protein production, working with insulin (which also controls blood sugar levels) to get the job done.

Both leucine and insulin trigger something called the mTORc1 signaling pathway, which tells our cells to start making protein. This pathway acts like a control center, making sure we have enough nutrients and energy to build proteins. However, as we age, this process slows down. We tend to eat less protein, absorb fewer nutrients, and our muscles aren’t as responsive to the protein we eat. This leads to less protein synthesis and can contribute to sarcopenia (muscle loss) and weight gain. Hence, to compensate for the age-related decline in mTORc1 signaling, we need to consume a diet rich in essential amino acids like leucine.

• Muscle Stem Cells: Another issue with aging is that our muscles don’t repair themselves as well. Muscle stem cells (MuSCs) are like little magic wands that can turn into different types of muscle cells. Normally, they’re in a resting state until something wakes them up to start fixing damaged muscle. But as we get older, these cells don’t work as well because their surrounding environment changes.

There are studies that show that as we grow older, our physiological makeup changes, and that this affects the integrity of MuSCs. In studies with conjoined mice, the older mice that were connected to the younger ones showed much better muscle healing compared to old mice connected to other old mice. The scientists think this is because the younger blood provided a healthier environment, which helped the MuSCs in the older mice become more active and start repairing the muscles. Interestingly, the opposite effect also happens. When old muscle tissue is put into young rats, the muscle becomes weaker and loses mass.

This suggests that the environment around these stem cells plays a big role in their ability to regenerate muscle. But in older muscles, this environment isn’t as supportive, which impacts muscle growth and function.

Risk factors underlying SO

Several risk factors contribute to the development of SO, including:

• Aging: As people age, they naturally lose muscle mass and gain fat. This process accelerates in older adults, making aging a significant risk factor for SO. In fact, it is estimated that about 18% of older women and 40% of older men are affected by SO.
• Physical Inactivity: Lack of regular exercise, especially resistance and strength training, can lead to muscle loss, which, combined with excess caloric intake, can result in SO. A study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9074188/ showed that for middle-aged to older adults, higher levels of obesity were linked to lower physical activity. Moreover, people who exercised at least three times a week were less likely to have low muscle mass.  Regular exercise is a vital tool to shed those extra pounds, and also maintain muscle function in both genders. Physical activity may sound too exhausting for some of us. However, there are simple ways to incorporate it into your routine… check out our previous blog that discusses 5 key tips to add into your daily routine.
• Poor Nutrition: Inadequate protein intake and poor dietary habits can contribute to muscle loss and fat gain. A diet high in processed foods and low in nutrients also increases the risk. This is because these so-called ‘comfort foods’ can promote inflammation, which is linked to muscle degradation, and can worsen SO. To make matters worse, a poor diet can also affect our hormones that regulate metabolism and muscle mass, such as insulin and cortisol. By imbalancing their natural levels, a poor diet can contribute to increased fat storage and reduced muscle synthesis. Check out our previous blog that talks about strategies to promote weight loss.
• Chronic Inflammation: Conditions that cause chronic inflammation, such as obesity itself, can exacerbate muscle breakdown and promote fat accumulation, contributing to SO. And a diet rich in processed foods can contribute to chronic inflammation. So, what can you do to prevent this chronic inflammatory state? The key, of course, is a healthy diet and regular exercise. You can also try to incorporate certain anti-inflammatory herbs in your diet. Check out our previous blog on 9 super herbs to help fight inflammation. Also, check out this blog on the types of foods to eat to further fight chronic inflammation.
• Hormonal Changes: Declines in hormones like testosterone and growth hormone, which are important for muscle maintenance, can also increase the risk of SO, particularly in older adults. This study Choi et al (2024) found that men with low levels of testosterone had a higher rate of sarcopenia, obesity, and SO compared to those with normal testosterone levels. Specifically, low testosterone levels were linked to 2X more obesity, 2.5X more sarcopenia, and 4X more SO.  

So, there you have it! SO might sound like a mouthful, but understanding what it is and its risk factors are key to tackling it head-on. Remember, aging is a natural part of life, but how we approach our health can make all the difference. By staying active – no need for marathon training! – and nourishing our bodies with wholesome foods, we can combat muscle loss and keep that stubborn fat at bay. Don’t let the thought of exercise intimidate you; start small and find activities you enjoy. Whether it’s a brisk walk, dancing in your living room, or even gardening, every little bit helps! And don’t forget to check out our previous blogs for more tips on integrating healthy habits into your daily routine.