Should all animals eat a high-fat, low-carb diet?
Part One: The Basis for a High-fat DietConsider cattle, sheep, horses, gorillas, rhinoceroses, koalas, all of which are herbivores eating grass and leaves; lions, wolves, polar bears, all of which are carnivores eating other animals; and humans. Before continuing, I want you to ask yourself:
It's likely that you will classify the herbivores as low-fat dieters and the carnivores – particularly the polar bear – in the 'high-fat diet' class. But what about humans? Where do we fit? Those are the important questions today. In 1997 the Journal of Nutrition published a study of the dietary intake of Western Lowland Gorillas, as the authors considered that the diet of one of our nearest 'cousins' could have implications for our (human) health.[1] The Western Lowland GorillaThe Western Lowland Gorilla eats leaves from around 200 species of plant. These foods are low in fat and available carbohydrate, varied in protein and very high in total dietary fibre. Macronutrients, in grams per 100 grams of dry matter, were found to be:
Putting the available macronutrients in terms of calorific values we have:
On the face of it, therefore, it looks as if gorillas eat a very low-fat, high protein diet. But things aren't as clear cut as that. No mammal — not even the herbivores — has developed an enzyme that will digest vegetable fibre. This is why we tend to discount it when calculating our calorie intakes. However, while mammals have not developed an enzyme that will digest fibre, there are lots of micro-organisms and bacteria that can the job for them. The herbivores employ billions of these bacteria. Comparison between Man and gorillaYou will note in the picture on the right that there is a marked difference in shape between a human and a gorilla. But the gorilla's gut is not only much larger than a human's, it also has an entirely different design. Human
Gorilla
This difference is highly significant. In a herbivore such as the gorilla, the caecum and colon harbour huge colonies of bacteria which ferment carbohydrates, particularly fibre, and use it to produce short chain fatty acids (SCFA) — principally acetic, proprionic and butyric acids. These are then absorbed into the body to be used as a source of energy. If we look at the gorilla's diet, we now see that the authors of the study into the western lowland gorilla's diet find that the fibre provides some 1.5 kcals of energy per gram of fibre, in the form of SCFA. As the fibre averages about three-fourths of the gorilla's diet, this energy forms a highly significant proportion of the gorilla's total energy intake. These SCFAs must be added to the fats already present in the gorilla's diet, which gives us the following proportions: Overall energy This gives totals of:
In other words, although the western lowland gorilla's diet, exclusively of leaves, looks like a very low-fat, carbohydrate-rich diet, it is actually a high-fat, moderate-protein, low-carb diet. Reference1. Popovich DG, et al. The Western Lowland Gorilla Diet Has Implications for the Health of Humans and Other Hominoids. J Nutr 1997; 127: 2000-2005. Part One: The Basis for a High-fat Diet | Part Two: Digestive difference between herbivores and carnivores | Part Three: Diet and disease
Last updated 7 July 2009 |
