After having been vilified for years as useful but tasty nutrient, fats have been embraced again. Contrary to carbohydrates, fats are not just an energy source, but building blocks for the entire body and of utmost importance for immunity and a proper working brains.
Furthermore, strongly reducing carb intake is one of the best decisions to make when combatting diabetes or undesirable cell replication. Consuming more fats is not entirely without risks. Fats are very compact and there is a good chance you will ingest more calories, than your body needs for maintenance, especially when you consume the tastiest combinations of fats with starches or sugars.
Even when you'd be so fortunate to need a lot of calories, the next hurdle is the risk of ingesting more fats than your stomach can digest, because fatty foods literally start fermenting in your stomach when they have to stay there for too long. This happens, because the rate at which fats leave the stomach is severely limited so that fats are not digested too rapidly and enter the blood stream or lymphatic system at once.
Once in the duodenum there is a limited availability of bile, that is needed to create fat droplets, small enough to be 'attacked' by fat-digesting enzyme lipase. Without adequate amounts of bile (stored in the gall bladder) only half of the fats consumed, can be absorbed.
Only the short and medium chain fatty acids, such as present in MCT-oil and coconut oil do not need bile, because this type of fat is small enough to be digested directly by lipase. This is why those fats are 'rapid fats' and a great fast energy source in low carb diets. In breast fed babies, fat digestion already starts in the mouth, because mother's milk not only consists of short- and medium chain triglycerides but also provides as extra digestive enzymes. This results in a much higher than usual absorption of essential cholesterol for normal growth and development of babies.
By contrast, less than 25% of nutritional cholesterol is absorbed by adults. It should be quite evident, that while fats are essential for good health, there is no good reason to raise intake to absurd heights, unless you want to be struck by indigestion. You are better served to limit the tasty starch-fat combinations and only consume a handful of healthy nuts at the same time.
Bile is produced in the liver, where it is conjugated with either taurine or glycine to form bile acids. Bile acid has both lipophilic and lipophobic properties , which allows them to form micelles and break down chunks of fats into smaller droplets, in much the same way as soap does. Bile is created from cholesterol: at least half of the daily production of cholesterol is to create bile and humans make as much as 18 grams of bile each day, mostly after meals. Most of the bile is not excreted but re-absorbed and transported back to the liver.
Apart from emulsifying fats, another important role of bile acids are to emulsify fat-soluble vitamins and other nutrients. This is the main reason why multivitamins and most other supplements are to be taken with a fat-rich meal, so that enough bile is excreted to absorb fat soluble ingredients.