By Coach Steve
Optimal fueling for our bodies during endurance sports is a complicated
topic. We all need some fat in our diets for our bodies to function
properly, but as endurance athletes we also need it to fuel our
training and racing. Fat is necessary for our bodies to synthesize
hormones, chemical messengers that activate various bodily functions.
Most nutritional counselors recommend that sedentary individuals
consume no more than 15% of their total calories as fat. Many exercise
physiologists differ on this opinion, recommending anywhere from
15% up to 30%. The higher values may be necessary for endurance
athletes given the amount of energy we need to fuel training and
racing in addition to our everyday activities. During aerobic endurance
training we burn some proportion of fat simultaneously with glycogen
(the stored form of carbohydrates). The ratio of fat to carbohydrate
we use is entirely speed dependent. At moderate speeds we utilize
a higher proportions of fat to glycogen. As we go faster, the mix
becomes progressively more biased toward glycogen usage.
This makes sense when we consider the example of the IronMan distance
athlete's metabolism. Physiologists know that well-trained athletes
can store only about 2000 (glycogen) calories within their muscle
tissue and liver. This is enough to get you through about 2.5 hours
of very intense racing. Athletes can't digest carbohydrates fast
enough to keep up with the caloric demands of a high quality IronMan
effort on glycogen stores alone. My relatively lean (~7% fat) body
has approximately 32,000 calories of stored energy as fat (I can't
safely use all the calories, but I won't need to). If I keep a reasonable
pace, I have several times the caloric energy (with the help of
stored fat) that I need to complete an IronMan. If I'm daring (or
foolish) and go very (too) fast, I'll burn too high a proportion
of carbs and only a little fat. This is the scenario where athletes
bonk and "lose it" before the finish. Meanwhile, if I cruise along
at a relatively comfortable pace, I can cover 140.6 miles in a day!
Consumption of some dietary fat is important for endurance athletes.
Training and racing for Olympic distance athletes probably doesn't
require a higher level of fat intake for optimal performance, but
that may change for IronMan training and racing. Generally, keep
fat intake lower during the off-season's lower volume of training,
but a little higher during heavy in-season training.
The ratio of fat, carbohydrates, and protein we consume on a daily
basis is important, but even more critical are the types of fat.
Saturated fat is the bad stuff; you can check any food label to
find out if it's there and in what proportion. Unsaturated fats
are the healthier ones to eat, and these can be mono- and poly-
unsaturated fats, or omega oils from nuts, seeds, or fish. The fats
from animal sources (excluding most fish) are saturated. Animal
sources include all meat and dairy products. Poultry is a little
better than red meat due to its lower overall fat content. The tropical
oils (e.g., palm kernel, coconut, and cottonseed) should be avoided.
These are cheap for food manufacturers, and are used in many processed
foods like cookies and other baked goods. Most other vegetable oils
are not as bad, except hydrogenated and partially hydrogenated vegetable
oils, which should be avoided. These are also known as trans-fats
because hydrogen is added and the molecule becomes stiffer as its
molecular shape changes from 'cis' to 'trans'. Hydrogenated fats
give processed foods a longer shelf life; fresh foods are always
better for you. Olive oil and canola oil (Canadian flaxseed) are
definitely the best to consume in processed foods and use in cooking.
Canola is great because it has virtually no taste, while olive oil
Try to be selective about which fats you consume. Stay away from
saturated and hydrogenated fats by choosing foods with predominantly
unsaturated fats. Also, avoid heavily processed foods that have
to sit on the shelf for a long time before they get to you.
Here's a brief explanation of fat (lipid) blood values. There are
two major tests that doctors can perform to assess whether you're
consuming too much saturated fat. The better known is the cholesterol
test. This simply measures the amount of serum cholesterol you have,
and generally should not exceed 200 mg/dL (all of our bodies produce
and need some cholesterol, but too much is bad). The more important
test value is your ratio of high-density lipoproteins (HDLs) to
low- and very-low density lipoproteins (LDLs and VLDLs). HDLs are
good and allegedly can even scavenge plaque off vessel walls. VLDLs
and LDLs are bad and contribute to blood vessel occlusion. Therefore,
a ratio where HDL is high relative to LDL is what we want to achieve.
The good news is endurance athletes seem to have slightly higher
levels of HDLs simply because of their training. Your eating habits
can enhance endurance performance as-well-as help you live longer!