1. Torture de France
2. Breathing training
3. Incredible eating machine
4. Exercise: Healthy for you and me?
Eating enormous amounts of bread, rice,
pasta, and similar carbohydrates has long been part of the endurance
athlete's over-inflated menu. Is the faith in "carbo-loading" misplaced?
Should more fat be added to the mix? Photo:
Lance Armstrong (left) and teammate Roberto
Heras gut their way uphill on stage of the 2003 Tour de France. On that day, Armstrong took
the lead and never relinquished it. Photo
by Graham Watson, courtesy Trek
Athletic heresy: Could high-fat foods help
fuel endurance athletes? Photo by Jeff Miller for UW-Madison
The 20 stages of the Tour de France are a period
of intense eating. Lance Armstrong, for example, will eat 6500 to
7000 calories per day. (Caution: Professional gourmand on closed diet. Do not try this at home!
Most civilians eat fewer than 3,000 calories a day.)
can get calories in carbos, fats, or proteins. What's the best source
for endurance sports?
we answer this tough question, allow us to stall. Muscles get hill-climbing
power from the chemical ATP, which they must make almost continuously
during exercise. ATP, in turn, must be replenished by oxidizing
sugar, fat, or protein. Preferably, these compounds are already
stored inside the muscle cell, but they may also enter the cell
from the blood.
ATP can be made by aerobic (oxygen-using) and anaerobic (without oxygen) processes. From here, matters get complex rather fast. For our purposes, the basic goal of endurance training is to improve mainly the aerobic mechanism, as that's the source of power by the hour.
terms of fuel, Robert Mazzeo, a professor of integrative physiology
at the University of Colorado, says the key goal before an endurance
race is to store glycogen, a readily oxidized sugar, inside muscle
cells. Muscle glycogen levels before a performance, he says, "are
a very good predictor of how you will perform."
That recognition, together with athletes' seat-of-the-pants experience, underlies the widespread practice of carbo-loading -- gobbling buckets of carbohydrate-rich food on the days before a race, to increase stores of glycogen inside muscle cells. Studies show that three days of carbo-loading roughly doubles stored glycogen.
The good news is that you might be able to carbo-load in a one-day orgy of rice, potatoes and pasta, rather than the traditional three-day regime. An Australian study of trained athletes, for example, found that all the gain of a three-day carb spree occurred in the first day (see "Carbohydrate Loading in Human..." in the bibliography).
The bad news is that carbo-loading may not be all it's cracked up to be. Timothy Noakes and colleagues in Australia found that cyclists riding a 100-kilometer course produced similar times, and power outputs, after a carbo-loading spree, and after eating mock carbs (we don't even want to think what they might be). The benefits of carbo-loading, the authors wrote, may grow from the placebo effect (see "Carbohydrate Loading Failed..." in the bibliography).
(Why all this focus on endurance in Australia? Maybe because it's the only continent anybody ever ran around -- just for kicks.)
A second area where conventional wisdom may be overturned concerns fat in the diet. Traditionally, endurance athletes have preferred a low-fat diet, convinced, like many health-conscious people, that it will control weight and improve blood fat levels. Riders in the Race Across America, for example, often eat a diet that provides 10 percent of calories from fat.
not going to assess the emerging counter-argument against the low-fat diet. But is low-fat the best path to surviving an endurance
event like the Tour de France?
Given the topsy-turvy nature of nutrition advice, we're not shocked to hear that fat may have a role. Peter Horvath, an associate professor in physiology and biophysics at the State University of New York at Buffalo, observes that muscle cells can get energy from their stores of fat, not just glycogen. Many muscles, in fact, "prefer" fat in the form of triglyceride over glycogen.
(We regret to inform you that the huge stores of fat on your thighs or gut can't be mobilized quickly enough to win an alpine climb. Exercise may help remove them, but slowly, slowly...)
As we've mentioned, different energy sources
are metabolized in different ways, and while glycogen may be the
fastest fuel to be burned, Horvath notes that in a long race, a
biker's energy rises and falls, depending on the incline, wind,
and the presence of riders to break the wind. "They will use a mix
of those fuels, and the best place to get that mix is inside the
muscle," from triglyceride as well as glycogen.
There is some evidence backing the claim. For
example, in a South African carbo-loading trial, bikers who had
eaten a high-fat (more than 65 percent of calories from fat) diet
were faster on a 100-kilometer ride (see "High-Fat Diet Versus Habitual..."
in the bibliography). And a Swiss study
found a 21 percent increase in running endurance among male runners
who ate a diet containing 40 percent of calories from fat, compared
to 18 percent (see "Muscle Structure ..." in the bibliography).
For comparison, Americans average 30 percent to 40 percent of calories
a study funded by a candy company (see "The Effects of Varying..."
in the bibliography), Horvath compared
diets containing 16 percent, 31 percent and 44 percent fat. The
average runner's endurance was 14 percent greater on the medium-
and high-fat diets, he reported.
High-fat is not the conventional wisdom, Horvath
concedes, but he says a diet with 30 percent to 40 percent of calories
from fat may be the coming thing. "It's controversial, but most
people will say that consuming adequate fat, and training, will
increase the intramuscular level of triglycerides, and the ability
to utilize those triglycerides."
Finally for endurance athletes, carbs may not be the whole answer. Tour de France riders, Horvath says, "consume an incredible amount of calories, have a huge caloric need. Nine thousand calories from spaghetti? It's impossible." (In fact, we read that Tour riders eat up to 7,000 calories, but the point remains).
It is that demand that sparks midnight refrigerator raids during the Tour, where ice cream by the liter disappears into the yawning yaps of famished cyclists.
A license to eat fat is welcome news here at
The Why Files, but let's read the fine print. First, we are talking
about endurance athletes who persistently pound the pedals or pavement.
Second, we are not talking Southern fried chicken. "One thing you
want to push is that you don't want them to consume trans fats,
lousy fatty acids, " says Horvath. "The fat we advocate is monounsaturated
fat, found in peanuts, olive oils, chocolate."
Finally, a bit more fine print. The notion is not universal among people who study endurance athletes. Horvath's view "is in the minority," says Robert Mazzeo of the University of Colorado. "You will find about a thousand studies talking about the importance of carbohydrates ... for weeks before a race. There are only a few studies, not very well supported, showing that it would help endurance performance from a high-fat diet. Fat, really, is a very minor factor."
But if Mazzeo and Horvath dispute the importance of fat in an endurance athlete's diet, they concur on the high-fat, high-protein, low carbohydrate craze called the Atkins diet. "Atkins, for an endurance athlete, would be the kiss of death," says Mazzeo. "The amount of glycogen in muscles dictates how long that person, can run, cycle or swim, before fatigue."
"When you talk about athletes, Atkins is just wrong," agrees Horvath. "The whole purpose of Atkins is to reduce carbohydrate use...but you need carbohydrate to burn fat completely. If you don't have carbohydrate, you don't burn fat completely... There is no question that an athlete needs glycogen stores in the muscles and liver, and the purpose of Atkins is to get rid of those."
How healthy is exercise for us mortals?