Health tips humans can learn from orangutans’ diets

They found that, be it feast or famine, the primates adapt with "flexible" eating patterns.

The critically endangered great apes' survival strategies in their native rainforests of Indonesia and Malaysia offer valuable "lessons" for human health and diet management, according to the American-led international research team.

The study shows that the primates are "marvels of adaptation" to the vagaries of food supply in the wild, and outshine modern humans in avoiding obesity through their balanced choices of diet and exercise.

The findings, published in the journal Science Advances, were based on 15 years of first-hand observations of wild orangutans in the jungles of Borneo.

Study leader Professor Erin Vogel, of Rutgers University, New Brunswick, said: “These findings show how wild Bornean orangutans adapt to changes in their environment by adjusting their nutrient intake, behavior and energy use.

“The work highlights the importance of understanding natural dietary patterns and their impact on health, both for orangutans and humans.”

She explained that orangutans are one of the closest living relatives to humans, sharing a common ancestor.

The evolutionary relationship means that orangutans and humans have similar physiological and metabolic processes, dietary needs and behavioral adaptations.

Vogel says studying orangutans can provide "insights" into the evolutionary adaptations that might also be relevant to humans.

She says humans also exhibit metabolic flexibility, but modern diets high in processed foods can disrupt the balance, leading to metabolic disorders such as diabetes.

Vogel said that while orangutans reduce physical activity during low fruit periods to conserve energy, humans - especially those with couch potato lifestyles - may not adjust their energy expenditure to match their calorie intake, leading to piling on the pounds and linked health issues.

She said, “Understanding these adaptations can help us learn more about how humans can manage their diets and health.

“It also highlights the importance of conserving orangutan habitats to ensure their survival.”

The research was conducted at the Tuanan Orangutan Research Station in the Mawas Conservation Area in Central Kalimantan, Indonesia, on the island of Borneo.

The conservation area, a peat swamp forest, protects about 764,000 acres, an area around the size of Rhode Island.

Peat forests are richly biodiverse, ancient ecosystems with landscapes dominated by waterlogged trees that grow on layers of dead leaves and plant material.

Vogel says understanding the dietary strategies of orangutans can inform better nutritional practices for humans.

She said: “In essence, the research on orangutans underscores the importance of dietary balance and metabolic flexibility, which are crucial for maintaining health in both orangutans and humans.

“It suggests that modern dietary habits, characterized by high consumption of processed foods rich in sugars and fats, can lead to metabolic imbalances and health issues.”

Earlier studies by Vogel and her colleagues established that orangutans prefer to eat fruit because it is rich in carbohydrates.

But when fruit is scarce, they switch to eating more leaves, bark and other foods that can provide more protein but fewer sugary carbohydrates.

In times of high fruit availability, orangutans still consume protein but get most of their energy from carbs and fats in the fruit.

Vogel said, “We wanted to find out how their bodies handle these changes.

“We tested how the availability of fruit affects their diet and how their bodies adapt to avoid energy imbalance.

"We looked at how they switch between different types of fuel – like fats and proteins – when preferred food availability changes.”

To conduct the study, the research team collected data for more than a decade on what the orangutans ate daily, and analyzed their urine to see how their bodies responded to any nutritional changes.

The findings showed that the great apes avoid obesity as part of a response to the significant fluctuations – in both magnitude and duration – in fruit availability in their natural habitat.

Vogel said: "Unlike humans in Western culture, who have constant access to high-calorie foods, orangutans experience periods of both abundance and scarcity.

"The periods of scarcity and resulting low caloric intake, similar to humans’ intermittent fasting, may help maintain their health by reducing oxidative stress."

The findings also showed that, during periods of fruit scarcity, orangutans exhibit "metabolic flexibility" - switching to using stored body fat and muscle protein for energy, allowing them to survive when food is scarce.

During periods of fruit scarcity, the apes also exhibit "behavioral adaptability" - relying on reduced physical activity as well as stored energy and muscles to conserve energy.

Vogel said: "They rest more, go to sleep earlier, travel less, and spend less time with other orangutans.

"This flexibility enables them to use body fat and protein for fuel when needed. They rebuild fat reserves and muscle when fruit availability is high."

She added: "The orangutan diet also prioritises a consistent level of protein, which contrasts with a modern Western diet, which often can be rich in low-cost, energy-dense, protein-poor foods.

"Those choices contribute to obesity and metabolic diseases in humans."