Gorillas are some of the most impressively muscular animals on the planet, but they don’t actually eat much protein compared to humans. If you’re wondering how these gentle giants get so jacked while munching on plants all day, read on.

If you’re short on time, here’s the quick answer: Gorillas build muscle through genetics, constant foraging giving them an active lifestyle, and getting enough calories from the large volumes of fibrous vegetation they eat.

Gorillas Are Genetically Predisposed to Being Muscular

More efficient muscle building

Gorillas have several genetic adaptations that allow them to build muscle more efficiently than humans despite a mostly vegetarian diet that is low in protein. For one, gorillas have a higher number of muscle fibers per unit area of muscle than humans, giving them the potential for greater muscle growth (Jozsa et al., 1989).

These extra muscle fibers allow them to gain strength without having to grow larger muscles.

Additionally, gorillas have longer muscle fibers and shorter tendons than humans, enabling more force production with less energy expenditure (Payne et al., 2006). Their muscles also have a greater number of capillaries (small blood vessels) per fiber, facilitating more efficient oxygen delivery and waste removal.

Moreover, some studies suggest gorillas may use protein and other nutrients more efficiently for muscle growth due to genetic differences influencing metabolism and hormone levels (Antón et al., 2006).

For instance, subtle variations in the leptin hormone, which regulates appetite and calorie burning, might give gorillas greater muscle-building capacity.

Higher levels of testosterone

In addition to their genetic predisposition for efficient muscle growth, gorillas simply produce more of the key muscle-building hormone testosterone. Adult male gorillas have testosterone levels 3-4 times higher than human men (Czekala et al., 2003).

This gives them an extra advantage for boosting strength, muscle mass, and physical performance.

High testosterone also triggers other anabolic, muscle-building processes in the body like increased protein synthesis. At the same time, it limits catabolic processes like muscle breakdown. Furthermore, rising testosterone levels during the gorillas’ adolescent growth spurts activate specialized stem cells called satellite cells that differentiate into new muscle fibers (Storer et al., 2003).

This enables genetically-elevated testosterone levels to amplify developmental muscle growth.

While their muscular frames have genetic underpinnings, dominant male gorillas also maintain youthful testosterone production and muscular physiques in adulthood through behaviors like fighting challengers for group dominance.

Keeping up their strength and intimidating appearance helps them retain breeding privileges and protect their troop.

Gorillas Are Constantly Active Through Foraging

Spend over half their day feeding

Gorillas truly are eating machines, spending over half of their day, around 9.5 hours, consuming various plants to fuel their large, muscular bodies (National Geographic). Their diet is almost exclusively herbivorous, composed of fibrous vegetation like wild celery, nettles, thistles and some fruits (African Wildlife Foundation).

This requires a large amount of time chewing and digesting to meet their caloric needs. An average male adult gorilla needs to consume around 30-50 lbs of vegetation each day, which could take 72,000 individual chews! (The Gorilla Organization).

So from early morning until dusk, wild gorillas are almost continuously preoccupied with grazing, foraging and feeding on their leafy goodness.

Travel between food sources

A typical gorilla troop inhabits a territory of a few square miles within tropical rainforests. This space needs to contain sufficient and sustainable food sources to support their plant-based needs. So each day consists of periods of feeding interspersed by travel between sites across their domain as they deplete the vegetation in one area and move to the next verdant spot.

Male gorillas can eat up to 40 lbs in a single meal, quickly exhausting the availability of local edible plants (Live Science). The movement between feeding areas helps the habitat regrow and prevents overforaging.

This keeps the gorillas in motion on their knuckles for around 1 mile of travel per day, using their powerful arms to support their weight between snacks (Wild Gorillas).

Climbing and additional movement

Though they spend much time on the forest floor grazing, gorillas frequently climb trees too. Both for feeding purposes and daytime rest periods, gorillas ascend trees easily up to 30 feet using their arms. Young gorillas especially seem to enjoy frolicking and swinging acrobatically from branches.

This arboreal activity further adds to their physical exertion throughout the day. And their strong arms allow them to build sleeping nests high up by easily snapping thick branches. Besides feeding and climbing, interactions within their social troops involves displays of power and battles between mature males.

So gorillas spend much of their day actively foraging fueled by lots of movement and low-protein vegetation, which contributes to building their characteristic powerful muscles (National Geographic).

Gorillas Get Enough Calories From Large Quantities of Plants

Up to 40 pounds of plants per day

Gorillas are able to build substantial muscle mass by consuming massive quantities of low calorie plant matter on a daily basis. An adult male gorilla eats up to 40 pounds of vegetation every day, opting for easy-to-digest roots, shoots, fruit, and bark over fibrous leaves (National Geographic).

This huge daily diet provides adequate calories for gorillas to engage in muscular activities like climbing, fighting, and chest beating displays.

Fibrous plants still provide fuel for muscle

Though plants are not protein-packed, the sheer volume gorillas ingest supplies the calories they need. Even tough fibrous plants provide fuel for muscle development once digested. By dedicating over half their day to eating, gorillas consume enough plant matter to sustain their active lifestyle and substantial 400 pound body weight.

This is aided by a digestive tract adapted to maximize the intake of nutrients from vegetation (ScienceDaily). So while their diet is low in protein compared to carnivores, dedicated grazing on huge quantities of plants gives gorillas the energy to maintain and use impressive muscular strength.


While gorillas don’t eat much protein compared to humans, their genetics, active lifestyles, and large quantities of fibrous plant food allow them to build substantial muscle mass. Understanding how these peaceful primates get so muscular can provide insights into nutrition, fitness, and the capabilities of our closest genetic relatives.

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