Any bodybuilder will tell you dietary protein is their “go to” macronutrient for building muscle. So fixated are athletes and bodybuilders on protein that it has spawned numerous lines of easy-to-take protein supplement powders – from whey to casein and soy, active people want their protein.
No doubt, some bodybuilders consume more protein than they need for muscle growth. The American diet is already relatively high in protein. If you’re a sedentary person, around 0.8 grams of protein per kilogram of body weight is the recommended quantity. Although debatable, many fitness coaches, trainers, and experts believe you may need up to twice that amount if you do intense resistance training or sustained endurance exercise, like long-distance running.
What you hear less about are the protein needs of older adults who resistance train, those over the age of 55. If you fall into that category, you also need more protein to build lean body mass due to a phenomenon called anabolic resistance.
What is Anabolic Resistance?
You’ve probably heard of insulin resistance but are less familiar with the concept of anabolic resistance. Like insulin resistance, anabolic resistance is where cells don’t respond as well as they should to a certain stimulus. In the case, of insulin, cells don’t take up glucose as readily even in the setting of plenty of insulin. With anabolic resistance, muscle cells are slow to respond to cellular signals that tell them to make new muscle proteins.
When you have anabolic resistance, your muscle cells are slower to ramp up protein synthesis in the face of anabolic stimuli such as resistance training, hormonal stimulation, and dietary protein. For muscle cells to build new proteins, anabolic genes need to be turned on, and a muscle protein synthesis pathway called the mTOR pathway activated. With anabolic resistance, it takes more stimulation to turn this integral pathway on. In other words, you need more protein to set in motion the synthesis of new muscle tissue. The amount of protein you consumed when you were younger and less anabolically resistant is no longer sufficient.
What causes anabolic resistance? It’s a phenomenon that becomes more common with age. We still don’t know the EXACT cause of anabolic resistance. Some research suggests that insulin resistance and the resulting inflammation that goes along with it contribute to anabolic resistance at the level of the muscle.
One thing that is apparent is leucine, one of the branched-chain amino acids, is a major regulator of muscle protein synthesis. Insulin is also involved in building new proteins, although not directly. Insulin “primes” muscle cells for new protein synthesis, partially by dilating blood vessels that feed into muscles, allowing more efficient delivery of nutrients. Another theory is that older muscle cells are less responsive to insulin and this disrupts normal muscle protein signaling. Interestingly, anabolic resistance is more common in obese people. Since fat produces inflammatory molecules, this strengthens the idea that inflammation at the level of the muscle is a factor. Physical inactivity in and of itself is also a contributor to anabolic resistance.
If inflammation is a key factor, you might wonder whether dietary components or supplements that reduce inflammation would improve anabolic resistance. Researchers have wondered the same thing. One such dietary component, long-chain omega-3 fatty acids, are promising. In one study, long-chain omega-3s boosted protein synthesis by 50%. These are the same omega-3s you get from eating fatty fish like wild-caught salmon.
How do omega-3s help anabolic resistance? For one, by reducing inflammation. Researchers also believe omega-3s change the fluidity of cell membranes in such a way that the receptors are more responsive to anabolic signals. If that’s the case, older adults may benefit from getting more dietary long-chain omega-3s along with more high-quality protein.
Since the branch-chain amino acid leucine is the “head honcho” for turning on muscle protein synthesis, getting more of this amino acid is also helpful. In general, there’s more leucine in animal foods like beef, pork, chicken, seafood, and cheese, but it’s also in soybeans, beans, seeds, and nuts. You just have to eat more of these foods. Plant-based foods usually contain less leucine but soybeans and soy-based foods are high in leucine, ranking just below eggs. At the top of the chart is whey protein, being almost 11% leucine compared to 8.8% for eggs and 8.0% for soybeans.
Research suggests that around 3.2 grams of leucine corresponds to the minimal threshold for turning on muscle protein synthesis. The amount of a particular protein food you’ll have to consume to get that amount of leucine varies with the protein source you’re eating. You can find lists of how much leucine is in foods online to get an idea of how much leucine you’re getting. It varies from 25 grams of protein to 40 grams, depending on the protein food you’re eating.
One thing that is clear is anabolic resistance is a phenomenon that needs more research because it contributes to one of the more serious problems of aging – sarcopenia. When older adults lose muscle mass and develop a high fat to muscle ratio, it leads to frailty and loss of functionality. That, in turn, contributes to disability and mortality.
Based on what we know now, here’s what you can do to overcome anabolic resistance:
. Do high-intensity resistance training to maximize anabolic hormone release.
. Increase the amount of protein in your diet. Get the equivalent of 3.2 grams of leucine within an hour after a workout.
. Do aerobic exercise too. This helps by reducing insulin resistance. Remember, insulin is a muscle protein synthesis “primer.”
. Eat fatty fish, like wild-caught salmon, twice a week or take 2 grams of long-chain omega-3s daily.
. Get your body fat and weight down to the normal range as much as you can. Having excess body fat fuels inflammation.
The Bottom Line
Yes, you do need more protein to build muscle later in life due to anabolic resistance but doing so can help you avoid the pitfalls of sarcopenia too. Keep lifting and eating your protein!
References:
J Cachexia Sarcopenia Muscle. 2012 Sep; 3(3): 157-162.
Am J Physiol Regul Integr Comp Physiol. 2010 Jun;298(6):R1485-95. doi: 10.1152/ajpregu.00467.2009. Epub 2010 Apr 14.
Nutrition & Metabolism20118:68. DOI: 10.1186/1743-7075-8-68.
Layne Norton PhD on protein: how much and how often?
Nutr Metab (Lond). 2012; 9: 67. Published online 2012 Jul 20. doi: 10.1186/1743-7075-9-67.
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