Have you ever wondered how you managed to stay strong and slim in your twenties with little effort, only to wrestle to keep the same physique a decade or two later? The old adage, use it or lose it, rings true when it comes to muscle mass. Unfortunately, muscle — and along with it your metabolism — naturally decreases as we age.But as we get older, simply hitting the gym and using the elliptical a few times a week just won’t be enough. Here are a few of my favourite tricks to ensure that you keep your metabolically-active muscle mass through the years.Prioritize your proteinI’ve seen many patients who’ve been feverously hitting the gym for years without an increase in lean muscle mass but, within just a few weeks of boosting their protein intake, their muscle increases like magic – and with it, the number of calories they’re burning at rest.Between 27 and 41 percent of adult women have dietary protein intakes below the current recommended dietary allowance – which is really just the bare minimum.Ease off on the inflammationHigh levels of inflammation affect your ability to build and preserve your muscle mass by reducing your body’s ability to process the protein that you’re taking in.By controlling the development of low-grade inflammation in one study, researchers significantly decreased muscle mass loss in rats between 20 and 25 months. Combine a natural anti-inflammatory with weight training and you have a winning prevention combination.Get less radicalNot all free radicals are bad for you (your immune system actually creates them to fight off viruses), however they do become a problem when it’s greater than your body can handle. The result: unhealthy aging, cell damage and muscle dysfunction. If you’ve seen an apple turn brown after being cut, you’ve witnessed free-radical damage. However you may have noticed that if you squirt a bit of lemon juice (which is high in antioxidants) on that apple, it will remain crisp and white. Your body is the same.