Going Vegan in Your 60s? A New Study Says Watch Your Muscle, Unless You’re Lifting

Plant-based eating has a well-earned reputation for heart health and longevity. So it’s tempting to assume going vegan is an across-the-board win, especially later in life when you’re already thinking hard about aging well. But there’s a catch, and it’s one that matters a lot for anyone over 65.

A randomized controlled trial published in August 2026 in The American Journal of Clinical Nutrition put 72 healthy older adults, all 65 or up, into one of three groups for 12 weeks. One group ate their usual omnivorous (meat and veggie) diet. One group switched to a self-selected vegan diet, meaning they chose their own vegan meals rather than following a prescribed plan. The third group went vegan and added resistance exercise.

What happened? Nutritionally, the vegan group’s protein intake fell by 27.7 grams a day in week 1, and was still down 19.3 grams a day by week 12. The omnivorous group’s protein intake didn’t change at all. Even adding resistance exercise didn’t fix this part. Protein intake dropped by a similar amount whether people were lifting or not.

Predictably, the muscle decline followed for the vegan group. The vegan group lost 0.61 liters of thigh muscle volume and 1.15 kg of appendicular lean mass (the muscle on your arms and legs, the stuff most associated with strength and independence as you age). The omnivorous group barely moved, essentially flat on both measures. Muscle protein synthesis, the rate your body builds new muscle tissue, was also measurably lower in the vegan group (1.09%/day vs. 1.27%/day in the omnivorous group).

The vegan-plus-exercise group did a bit better: their muscle loss was significantly smaller: 0.35 liters of thigh volume lost instead of 0.61, and 0.62 kg of lean mass instead of 1.15. Muscle protein synthesis came back up too, to 1.24%/day, much closer to the omnivorous group’s number.

The catch here is that nobody told these participants exactly what to eat or handed them a protein target. It's not that plants can’t provide enough protein, it’s that most people switching to vegan on their own, without guidance, under-eat protein without realizing it, and 12 weeks was long enough for that gap to show up in real muscle tissue. This is a real problem in older adults where sarcopenia is a significant risk.

So, if you’re 65 or older and thinking about going plant-based, two things matter more than the diet itself. Hit your protein target deliberately (0.8-1.0g/lb of body weight), since it won’t happen by accident on a self-selected plan. On a vegan diet this will involve supplementing. And keep (or start) lifting weights, because resistance training cut this study’s muscle loss by nearly half even while protein intake stayed low.

Muscle mass and strength are two of the clearest predictors of independence as you age, and they’re exactly the kind of thing that erodes quietly if you’re not tracking it. Our Activate Your Age assessment measures body composition alongside cardio, strength, gait, balance, and reaction time, so a drift like this shows up in your numbers long before it shows up as a problem.

Want to know where you actually stand? Book an Activate Your Age assessment and build your plan around your real data.