It's generally assumed that for most terrestrial mammals, the main nutritional goal is to get protein. However, a group of researchers who spent years watching gorillas in the Congo have found evidence that this isn't quite the case. What they discovered is that the gorillas do have a thing for protein-rich leaves, and they devote most of their effort to foraging these leaves — but only during seasons where there wasn't much fruit. Contrary to the general scientific consensus, if it was fruit season, that's where there effort would go. Gorillas much preferred the sweet stuff to high-protein leaves.
What's interesting is that the seasonal switch between the two food types closely mirrors two views on human nutrition. During the heavy fruit season, the gorillas eat up to 40% of their diet of pieces of fruit, and 16% of their energy from protein — which matches what most humans like, and the recommendations for protein levels given by the America Heart Association. Conversely, during the winter when fruit can't be easily found, they switch to a protein heavy diet, where protein accounts for some 30% of their daily energy — which is what people who try to lose weight with high protein diets strive for.