With age, muscle mass gradually decreases. However, bodybuilding allows you to slow down this development and preserve your autonomy. It is still necessary to provide the body with sufficient protein to maintain and develop muscles. This is precisely what the researchers of the IMPACT trial wanted to examine, published online on September 22, 2026 in the research base of the Amsterdam University of Applied Sciences. Their question: does a vegetarian diet including eggs and dairy products allow you to develop as much muscle as an omnivorous diet after the age of 55?
Vegetarians or omnivores: both groups gained muscle
The researchers followed 108 adults aged 55 and over, with an average age of 66. Randomly divided into two groups, the participants adopted either a lacto-ovo-vegetarian diet (without meat or fish) or an omnivorous diet. All were required to consume at least 1.2 grams of protein per kilogram of body weight per day. They also followed the same muscle strengthening program: three sessions per week for 12 weeks.
The results, assessed in particular by a measurement of body composition (DXA), show an increase in muscle mass in both groups:
- Vegetarian group: + 0.38 kg on the arms and legs;
- Omnivorous group: + 0.66 kg.
Participants consuming meat therefore gained more muscle on average. But another result deserves attention: the two groups progressed comparably on tests of leg press strength and ability to get up from a chair. An important point for maintaining autonomy: maintaining your strength allows you to continue to perform everyday tasks, even as you age.
The difference was mainly in protein intake
How can we explain this difference in muscle gain? Part of the answer lies on the plate. Vegetarian participants consumed less protein than omnivores, despite a common nutritional goal:
- Vegetarians: 1.24 g of protein per kilo per day, 76% of which is of plant origin;
- Omnivores: 1.58 g/kg/day, of which 67% is of animal origin.
For a 70 kg person, this represents around 87 grams of daily protein for vegetarians, compared to 111 grams for omnivores. That’s almost 24 additional grams each day for the latter.
However, proteins constitute the raw material essential for the construction and repair of muscle fibers. With age, their intake becomes particularly important to compensate for the progressive decrease in muscle mass.
The observed gap could therefore explain, at least in part, the difference in progression between the two groups. This does not mean, however, that plant proteins would be incapable of nourishing the muscles: they simply require special attention to reach the necessary quantities.
Without meat, what foods should you choose to preserve your muscles?
The main lesson from this study is ultimately quite simple: eliminating meat is not enough, you still need to know what to replace it with. A vegetarian diet can cover protein needs, provided it does not rely primarily on vegetables and starchy foods.
Several foods allow you to diversify your plant protein intake:
- Eggs and dairy products: yogurts, cottage cheese and cheeses;
- Legumes: lentils, chickpeas, beans and split peas;
- Soy: tofu and tempeh, particularly interesting for their proteins;
- Oilseeds: nuts and almonds, which also contribute to intake.
A report from the French Food Safety Agency (Afssa, now Anses) published in 2007 already indicated that vegetarian diets including eggs and dairy products could ensure satisfactory protein intakes in children and adults. However, additional vigilance remains necessary among seniors, particularly when they wish to maintain or develop their muscle mass.
After 60, bodybuilding remains essential to preserve your autonomy
The IMPACT trial also delivers an encouraging message: it is possible to gain muscle after the age of 55, including without consuming meat or fish. The Manger Bouger recommendations recommend, after the age of 65, muscle strengthening activities two to three times a week, in addition to regular physical activity, balance and flexibility exercises. The recovery must nevertheless be gradual. The High Authority for Health (HAS) recommends adapting exercises to individual abilities and recommends a medical evaluation before starting a physical activity program of at least moderate intensity after the age of 60.
Should you give up a vegetarian diet to maintain your muscles? No. The trial failed to demonstrate that this diet performed as well as the omnivorous diet according to the statistical criteria used. But it also does not prove that meat is essential for progress.
Its limited duration (12 weeks) and the relatively modest number of participants (108) call for caution. The essential message remains encouraging: after age 55, preserving your muscles relies on regular training and sufficient protein intake. Whatever your diet, it is possible to act to maintain your strength and autonomy.