Animal world Research team investigates the metabolism of orangutans
Orangutans know when to strike: When there is plenty of fruit hanging, they eat in excess and store up fat for a rainy day. Researchers see parallels in this eating behavior to humans, who often eat too much. This is despite the fact that food is never in short supply.
29.08.2025, 15:16
SDA
This is shown in a new study published in the journal "Science Advances". An international research team with Swiss participation studied the behavior of orangutans on the Indonesian island of Borneo between 2003 and 2018. They also collected urine samples from the animals to analyze their metabolic activity. The research team was led by Rutgers University in the USA. Researchers from the University of Zurich were involved from Switzerland.
They showed that orangutans stuff themselves with energy-rich fruits, store fat and build muscle during periods of abundance. When the fruit disappears, the orangutans' bodies switch from digesting externally supplied (exogenous) nutrients for energy to processing internally produced (endogenous) nutrients - they use stored fat and muscle protein as a source of energy.
During these times, the animals switch their diet to protein-rich leaves, seeds and bark. At the same time, they save energy. They rest more, go to sleep earlier, move less and spend less time with other orangutans. This flexibility allows them to use body fat and protein as an energy source when necessary, and to rebuild their reserves when fruit availability is high.
Times of scarcity are lacking in many people
The researchers see this as a clear contrast to modern humans: Humans would have similar metabolic abilities in principle. While orangutans adapt their metabolism flexibly and adjust their behavior to scarce resources, many people today live in a world of constant food availability.
Instead of alternating phases of abundance with periods of relative scarcity, as was common in evolution, many people are constantly consuming energy-rich, highly processed foods - often low in protein but high in sugar and fat. The result is obesity, diabetes and other metabolic diseases, which are widespread in industrialized societies.
