Lipid (Fat) Digestion

Lipids take the longest to digest because of their insolubility in water as well as their complex structure. They are mainly digested in the intestines, and they take the longest to empty from the stomach (3-4 hours or more). Under normal conditions, about 60-70% of fat is absorbed via the lymph system. Medium and short chain fatty acids enter the blood stream and can be transported directly to the liver.

Once in the blood stream, fats and cholesterol are transported in conjunction with proteins. (lipoproteins). Fats that are not needed are converted to body fat. The liver is the main processing center for fats which can be used for energy and can be modified by shortening or lengthening as well as saturating or un-saturating. Liver cells also synthesize fatty acids. Fats are constantly broken down, resynthesized, and used for energy. Fats are in equilibrium when caloric intake is in balance with energy needs.

When caloric intake from fats, proteins, and carbohydrates exceeds energy expenditure body fat is increased.

What type of fats you ingest can effect your bodies composition of fatty acids. Studies have shown that vegetarians have bodies made up of primarily unsaturated fatty acids while meat eaters have bodies made primarily of saturated fatty acids. Saturated fatty acids tend to be more unstable than unsaturated fats which could make their cells more susceptible to free radicals and metabolic waste products. This means that bodies made up of more unsaturated fats may be more resistant to certain types of cellular damage.

We are not saying one should be vegetarian or carnivore. What we are saying is we ALL need to eat our vegetables in addition to varying our dietary fat sources regularly. Variety is our friend.

So how much fat do we need in our diet?

The National Research Council (NRC) recommends total fat intake stay below 30% of daily total calories and that saturated fat stay below 10% assuming you are only eating the recommended total daily calories for your age and body size. As for the essential fatty acids, the NRC recommends 1-2% or 3-6 grams. Some require three times this depending on hormone differences.

For athletes, the total amount of fat will vary depending on the sport, body size, and personal requirements. In general endurance athletes will need to maintain higher levels of dietary fat where power athletes require less. This is directly related to the energetics of the sport. In many cases, athletes of very active individuals consume 2-3 times the fat that would be considered “average”. See article on EPA/DHA.

Too much fat in our diets.

Most of us get far too much fat in our diets. The typical American consumes 45% of their daily calories from fat. When you consider that a gram of fat contains two times the amount of calories that a gram of carbohydrates contains, you can easily see why fat intake can be such a concern.

The American Heart Association suggests 30% of your total calories should be fat. For most of us anywhere between 20-30% of daily caloric intake would be appropriate. The rest should consist of lean proteins and complex carbohydrates. The closer one can get to this, the easier your fat loss and weight maintenance goals will be.

So, what are some good sources of healthy fats?

Lean proteins, primarily grass-fed and free-range sources are preferred. Plant sources of fat tend to be healthier than animal sources. (We are not telling you to not eat meat. We love meat. We are telling you to EAT YOUR VEGETABLES too! Plant sources of proteins are generally low quality and incomplete, so, a good balance of healthy animal proteins and plants will be the most favorable combination. A balance must be maintained in order to minimize saturated fats and high cholesterol sources.

  • Lean meats
  • Fish
  • Egg whites
  • Low fat milk
  • Chicken
  • Turkey
  • Any combo of plant sources of fat that help make complete proteins
  • Flax seed
  • Olive oil
  • Peanut oil
  • Cotton seed oil
  • Safflower oil
  • Sunflower oil
  • Grape seed oil
  • Most nuts

Minimize the intake of bacon, cream, mayonnaise, butter, etc.

Summary:

Excess body fat should be avoided, it just slows you down and leads to chronic disease. Keep daily fat intake to about 30% of daily calories. Minimize the intake of saturated fats and cholesterol. Eat low-fat meals before and after training (fat makes the stomach empty slowly preventing nutrients from getting into the body quickly). Include good sources of essential fatty acids such as EPA/DHA (fish oils).

There are really no BAD foods, some are just better than others. The most important thing is that anything in moderation, depending on the situation, can be okay.

Thomas Sampson CFL-3, USAW-2, Sports Nutritionist

International sports science association. Sports nutrition. 5th edition. 2018 carpinteria CA Nancy Clarks Sports Nutrition Guidebook. 4th edition. 2008 champaign IL