Indonesia - August 28, 2025 Borneo, Indonesia – Orangutans in the rainforests of Indonesia and Malaysia have mastered survival through remarkable dietary flexibility, offering valuable lessons for human nutrition and health. A Rutgers-led team observed wild orangutans in Borneo for 15 years, documenting how these critically endangered apes adjust their nutrient intake and behavior according to seasonal fruit availability. Their study, published in Science Advances, shows how orangutans maintain balance and avoid obesity, unlike many humans on modern diets. “These findings show how wild Bornean orangutans adapt to changes in their environment by adjusting their nutrient intake, behavior and energy use,” said Erin Vogel, Henry Rutgers Term Chair Professor in Anthropology at Rutgers. “The work highlights the importance of understanding natural dietary patterns and their impact on health, both for orangutans and humans.” Orangutans consume fruit when abundant for energy-rich carbohydrates and fats, and switch to leaves, bark, and other protein-rich foods when fruit is scarce. During low-fruit periods, they conserve energy by resting more, traveling less, and reducing social interaction—a strategy comparable to intermittent fasting in humans. Researchers collected daily dietary data and urine samples to study how orangutans metabolize energy, revealing that they switch between fat and protein stores when needed. Prioritizing consistent protein intake helps them maintain muscle and overall health despite fluctuating food sources. The study underscores the link between metabolic flexibility and long-term health, suggesting humans could benefit from understanding orangutans’ strategies for balancing energy, protein, and caloric intake. Vogel also emphasized the importance of conserving orangutan habitats, such as the 764,000-acre Tuanan Orangutan Research Station in Central Kalimantan, to support both species survival and ecosystem health. “Understanding these adaptations can help us learn more about how humans can manage their diets and health,” Vogel said.