Sarcopenia (in Greek, sarx for flesh and penia for loss) is considered, “poverty of the flesh” (Rosenberg, 1997). The term is used to describe the loss of skeletal muscle and progressive weakness that occurs with aging. Sarcopenia is also used to describe the associated changes in the nervous system, endocrine system, levels of inflammation, and body fat distribution, as well as poor nutrition and reduced physical activity that is associated with aging. The most prominent effects are greatly reduced mobility and loss of independence in the older population (Roubenoff, 2000).
Sarcopenia may develop as early as 30 years of age when body weight gain and accumulation of fat masks the outward signs of muscle loss (See figure below). Between 30 and 60 years of age, the average adult gains approximately 0.45 kg (1 lb) of fat and loses about 0.23 kg (0.5 lb) of muscle yearly. Loss of muscle mass then accelerates to 2% annually beginning at 60 years of age (Waters, 2010). The rate of muscle loss is variable, with a total muscle cross-sectional area reduction of about 40% between 20 and 60 years of age (Waters, 2010). The prevalence of sarcopenia increases from 13-24% in persons under 70 years of age then skyrockets to >50% in persons over 80 years of age (Baumgartner, 1998). The wide variability in the progression of sarcopenia is affected by age-related systemic changes and lifestyle choices (Rom, 2012).
Muscle wasting in a 74 year-old sedentary male and the absence of muscle wasting in a 70 year-old triathlete. The 74 year-old triathlete has muscle mass comparable to the 40 year-old triathlete (Wroblewski, 2011).
The sarcopenic sedentary lifestyle
The simplest view on the development of sarcopenia is explained by loss of muscle mass known as muscle atrophy. This muscle loss is due to physical inactivity that is common in modern life. Certain people that you may know may harbor the early signs of sarcopenia even before the age of 30, although research does not include them in the current definition. The simple absence of stimuli that promotes muscle formation may fundamentally explain age-related muscle loss (Roubenoff, 1999). A sedentary lifestyle with no increased energy expenditure above resting level such as sitting, lying down, and watching television has been shown to be a major risk factor for sarcopenia (Chastin, 2012).
Many studies have shown that prolonged periods of bed rest can result in a 30% reduction of muscle volume, particularly in muscles of the lower limbs in (Narici, 2011).
Exercise can reverse sarcopenia
It is never too late to reverse age-related muscle decline. A study looking at an eight-week strength training program in the 90-year-old age group demonstrated an over 100% increase in strength from the pre-exercise baseline and a 48% increase in walking speed (Fiatarone, 1990). Another study following a 12-week strength training program of three days a week in older adults resulted in increased muscle strength, muscle tissue hypertrophy, and increased myofibrillar protein turnover (Frontera, 1988). Even a resistance training program of only one day per week in older adults improved muscle strength in a similar manner to a resistance training program of 3 days per week (Taaffe et al. 1999).
A progressive resistance training program should be tailored to an individual’s goals. The program should be challenging, not overwhelming, and should be continuously adjusted to stimulate muscle growth. Orange Theory and CrossFit are good examples of programs that promote muscle development in continuously changing workout programs. Before starting any exercise program, it is important to check with your physician. If you are unfamiliar with strength training, starting off with a trainer is a good idea to gain familiarity and ensure safety with the exercises.
Resistance training is a form of exercise in which muscle contract against an external load. Examples of resistance training include free weights, exercise machines, body weight exercises, and use of elastic bands.
The classic resistance training program to build muscle consists of 8 to 10 exercises that target the major muscle groups, done in sets of 8 t o12 repetitions. The last 2-3 repetitions should be somewhat difficult at about 60% to 80% of a one-repetition maximum. To see changes, it is important to do this program two to three times per week, although in the previous study, even once per week is more beneficial than not participating at all.
Some people like to participate in high-intensity interval training (HIIT) which approximates the challenges in life like running for the bus or carrying a sudden heavy load. HIIT allows you to gain the benefits of exercise in a much shorter time frame.
Aerobic training, in which large groups of muscle are engaged for a prolonged period of time, is less likely promote increased muscle strength; however, it can increase the cross-sectional area of muscle fibers, mitochondrial volume, and muscle enzyme activity (Rom, 2012).
The American College of Sports Medicine and American Heart Association suggest a minimum of two non-consecutive days per week of strength training (Nelson, 2007).
Individuals with poor performance initially can achieve improvement even with less frequent training. Side effects are rare, but it is still advisable to review a new exercise program with your physician first especially if you have pre-existing diseases (Burton, 2010).
A very important study compared older and younger strength-trained subjects, the maximal isometric torques, the speed of movements, cross-sectional areas of muscle, as well as the content of muscle fibers called myosin and tropomyosin and found them to be identical. These findings suggest that strength training can be used to counteract muscle wasting related to age (Klitgaard, 1990).
Sarcopenia is caused by many lifestyle factors.
Diet is more important in sarcopenia than we ever imaged
Aging is associated with decreased food intake that has been called the “anorexia of aging” or in younger old population, “skinny fat”. A decrease in food intake is thought to play a critical role in sarcopenia (Morley, 2001).
Reduced food intake may be due to living alone with little or no support, a diminished interest in cooking, less hunger and thirst, chewing and swallowing difficulty, digestion problems, and inadequate absorption of nutrients.
Food choices are usually less than ideal with a reliance on convenient processed foods which are high in carbohydrate calories and low in healthy proteins, healthy fats, vitamins, and minerals. A similar effect occurs with an excessive caloric intake which leads to obesity, hiding the loss of muscle mass behind the fat called “sarcopenic obesity”. Excessive caloric consumption or storage creates chronic low-level inflammation and metabolic dysfunction which further exacerbates muscle wasting (Plutzky, 2009).
Animal protein provides the proper ratio of essential amino acids that are very important for building muscle (Volpi, 2003). Black beans and kidney beans contain similar ratios of essential amino acids except for methionine. Hence rice is consumed for the addition of methionine. The nine essential amino acids that humans cannot synthesize are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. But make sure you stay away from processed proteins due to the extra fillers and preservatives. Protein powders may be a good alternative if you have difficulty consuming enough protein daily.
Leucine, one of the essential amino acids has been found to be particuarly helpful in preserving muscle mass. Leucine is found in beef, lamb, pork, poultry, fish, dairy products, beans as well as nuts and seeds. Leucine has been found to play an important role in regulating muscle metabolism and is known to prevent muscle wasting (Rom, 2012 #1). A study that increased the proportion of leucine in a mixture of essential amino acids given to older subjects was found to reverse impaired protein synthesis in muscle (Katsanos, 2006).
The best protein-rich foods to consider adding to your diet include grass-fed and finished beef, organic chicken, wild fish such as tuna and salmon, organic whey protein, black or kidney beans, fermented dairy such as yogurt, kefir, and natto.
Older adults should eat nutritionally dense foods as the absorption of nutrients is usually impaired.
Older adults require more protein/kilogram body weight than do younger adults because older adults have lower rates of protein breakdown and synthesis (Nowson, 2015).
The current recommended daily allowance (RDA) for protein is 0.8 grams per kilogram (g/kg) for adults and the recommended dietary allowance (RDA) for protein is 1.0 to 1.3 grams per kilogram (g/kg) for older adults (Chernoff, 2004, Nowson, 2015)
Following exercise, your muscles are most receptive to nutrition so it is important to consume a drink or meal with some added carbohydrate and protein within 30 minutes of completing an exercise. This helps rehydrate and fuel your muscles to begin the muscle repair process.
A 2015 study in The American Journal of Clinical Nutrition found that omega-3 fatty acid supplementation from fish slowed the decline in muscle mass and function in older adults (Smith, 2015).
Hormones and sarcopenia work against each other
There is a great deal of debate around the modulation of growth hormone levels to promote muscle growth, so physicians have instead begun to assess thyroid and testosterone levels.
Older adults are at increased risk of vitamin D insufficiency due to various factors. As people age, the skin’s ability to synthesize vitamin D efficiently is reduced, and the kidney is less able to convert vitamin D to its active form; in addition, inadequate sunlight exposure which is essential for vitamin D synthesis and low consumption of dietary vitamin D are common among the elderly (Dirks-Naylor, 2011). Vitamin D plays an important role in skeletal muscle tissue by maintaining the function of the type II muscle fibers, to preserve muscle strength and prevent falls (Montero-Odasso, 2005).
Stress drives the sarcopenic process
Stress raises cortisol levels which promotes weight gain and sarcopenia, so it is important to maintain a healthy body weight and manage stress throughout life (Ferrucci, 2002). Stress is also increased with inadequate levels of sleep
Muscles wither away from alcohol
Alcohol impairs muscle protein synthesis. Lab studies have shown that ethanol decreased muscle protein synthesis by up to 75% (Tiernan, 1986). A disease called alcoholic myopathy occurs with pronounced or long-term alcohol intake in individuals with poor dietary intake and usually results in low muscle mass and strength, muscle cramps, gait dysfunction, and falls. If severe, it can result in acute alcoholic myopathy which is characterized by severe muscle pain and kidney failure. Chronic alcoholic myopathy is a common complication of alcoholism affecting approximately 50% of alcohol. Chronic alcoholic myopathy is associated with nutritional deficiencies or liver disease and is reversible within 6–12 months if ethanol intake is discontinued (Preedy, 2001).
Smoking guarantees muscle wasting
Smokers have been found to have lower skeletal muscle mass than subjects who never smoked (Szulc, 2004) and accelerated degradation of muscle protein in elderly smokers (Rom, 2012).
The summary of sarcopenia
In summary, you do not need to fear a condition named sarcopenia, but you do need to fear the first time it is challenging to get out of a chair, the first hard fall and the eventual loss of independence. Research has shown that it is never too late to strengthen your muscles even if you make simple changes like taking the stairs more often or exercising once a week,
References
Waters DL, Baumgartner RN, Garry PJ, Vellas B. Advantages of dietary, exercise-related, and therapeutic interventions to prevent and treat sarcopenia in adult patients: an update. Clin Interv Aging. 2010;7:259–70. http://dx.doi.org/10.2147/CIA.S6920.
