Gorilla's diet - fibre fermentation = a high-fat, moderate-protein, low-carb diet - Part One: The Basis for a High-fat Diet

Should all animals eat a high-fat, low-carb diet? - Part One: The Basis for a High-fat Diet:

"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. "

Comparison between Man and gorilla

You 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

• Small intestine is major organ used to extract nutrients.
• Small intestine ~ 50% of the total volume.
• Caecum and colon ~ 20% volume

Gorilla

• Ratios exactly the opposite
• Small intestine ~ 25% volume
• Caecum and colon ~ 53% volume.

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 2 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 
                                           (kcal) per 100g        %age
Protein                                   47.1                        20.5%
Available carbs                         30.6                      13.1%
Fat                                        4.9                        1.9%
SCFA from fibre                      148.0                      64.5%

This gives totals of:

• protein = 20.5%
• carbs = 13.1%
• fats = 66.4%

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. 

The Western Lowland Gorilla

The 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:

• Fat                                    0.5g (range 0.1 - 1.8)
• Available carbohydrate           7.7g (range 0 - 22.4)
• Protein                             11.8g (range 1.7 - 30.0)
• Fibre made up by far the major part of the plants ranging between 52.0g and 96.5g for a mean of 74.0g.

Putting the available macronutrients in terms of calorific values we have:

• fat                                     5.9%
• available carbohydrate            37.1%
• protein                              57.0%

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.