High fat diet improves performance, lipid profilie and immune function in endurance athletes

Several studies seem to suggest that relatively high fat
diets improve performance, lipid profile and immune function in endurance
athletes. Below a few news articles about studies conducted at the
University of Buffalo in 1994, 1997 and 1999 (references [31] and [29] in
the reference list at the bottom of this message):

Trained Runners Perform Better On Diet Moderately High In Fat Than On High-Carbohydrate, Low-Fat
Regimen, Study Shows October 25, 1994 <URL:http://www.buffalo.edu/news/fast-execute.cgi/article-
page.html?article=30860009>

Citations:

"Highly trained runners hoping to improve their performance by slashing fat from their diets may
be heading down the wrong nutritional path, a small pilot study by University at Buffalo
researchers implies.

[...]

Historically, researchers have agreed that a high- carbohydrate, low-fat diet is preferred for
maximum endurance during moderate-to-high-intensity exercise. Many of the studies supporting
this view have used untrained or moderately trained subjects, Leddy said. Those results may not
apply to trained runners because trained athletes metabolize fats more efficiently that
untrained persons, he noted.

Previous studies using a high-fat diet often severely restricted carbohydrates as well, Leddy
said, while carbohydrate levels remained at 50 percent of total calories even on the increased-
fat diet in this study.

To compare performance levels, UB researchers placed subjects on three different diets for one
week each, and conducted exercise testing at the end of each week. The three diets were:

Six male members of the UB track team took part in the study. The athletes were tested on
treadmills after each week’s diet to determine maximum oxygen consumption -- a measure of the
efficiency of one’s oxygen-transport system and an indicator of aerobic capacity -- and
endurance.

To eliminate any carry-over effect from the carbohydrate regimen, the runners consumed and were
tested on the higher-fat diet before the high- carbohydrate diet.

Results showed the athletes ran 20 percent longer on the high-fat diet than on the carbohydrate
diet, and 32 percent longer on the high-fat diet than on their normal diets.

Maximum oxygen consumption was 11.4 percent higher on the high-fat diet than on the high-
carbohydrate diet, results showed. ..."

High-Fat Diet Raises "Good Cholesterol" In Trained Runners January 21, 1997 <URL:http://www.buffalo.edu/news/fast-execute.cgi/article-
page.html?article=30850009>

A citation:

"Athletes training on a high-fat diet have a healthier cholesterol profile than when they eat
the traditional low-fat, high-carbohydrate training diet and they do not gain weight or body fat
in the process, new data from researchers at the University at Buffalo have shown. The study,
thought to be the first to show this effect in women, has important implications for anyone who
puts in high running mileage for health purposes. It shows they may be blunting the benefits of
running by eating a diet too low in fat.

Previous results from the same study group of athletes showed that increasing dietary fat also
improves endurance performance.

The new results, reported in the January issue of Medicine and Science in Sports and Exercise,
show that trained male and female runners who consumed a diet composed of as much as 42 percent
fat had higher levels of high-density lipoproteins (HDL) in their blood than when on a diet of
only 16 percent fat. HDL is the form of cholesterol known to lower the risk of coronary heart
disease. LDL, or low-density lipoproteins, is known as the "bad cholesterol" because it has the
opposite effect.

The runners, who trained at least 35 miles a week, did not gain weight on the high-fat diet or
show an increase in any risk factors for coronary heart disease. ..."

Very-Low-Fat Diet May Compromise Immune Function, Increase Infection Rate in Trained Runners, UB
Study Finds. Saturday, May 22, 1999 <URL:http://www.buffalo.edu/news/fast-execute.cgi/article-
page.html?article=27530009> <URL:http://www.sciencedaily.com/releases/1999/05/990528004622.htm>

Citations:

"Trained runners who severely limit the amount of fat in their diets may be suppressing their
immune system and increasing their susceptibility to infections and inflammation, a University
at Buffalo study has shown.

In findings presented here today (May 22, 1999) at the fourth International Society for
Exercise and Immunology Symposium, lead author Jaya T. Venkatraman, Ph.D., reported that
running 40 miles per week on a diet composed of approximately 17 percent fat compromised the
runners' immune response.

The medium and high-fat diets, composed of approximately 32 and 41 percent fat respectively,
left the immune system intact, and enhanced certain components, the findings showed.

"The data suggest that higher-fat diets may lower the proinflammatory cytokines, free radicals
and hormones, and may enhance the levels of anti-inflammatory cytokines," Venkatraman said.

[...]

"In general, moderate levels of exercise are known to enhance the immune system," said
Venkatraman. "But high-intensity exercise and endurance exercise produce excess levels of free
radicals, which may place stress on the immune system.

"Since we have shown that athletes perform better on a higher-fat diet than on a low-fat diet,
it was important to determine if the higher-fat diet would further compromise the immune
system," she said. "We found that it did not, but the very-low-fat diet did."

The study involved six female and eight male competitive runners who trained at 40 miles a week
and were part of a larger performance study. They spent a month on their normal diets, followed
by a month each on diets composed of approximately 17 percent, 32 percent and 41 percent fat.
Protein remained stable at 15 percent and carbohydrates made up the difference.

The immune status of the runners was obtained by analyzing concentrations of essential
components of the immune system -- leukocytes, cytokines and plasma cortisol -- in blood samples
taken before and after an endurance exercise test. The tests were conducted at the end of each
four-week diet period.

Results showed that natural killer cells, a type of leukocyte and one of the body's defense
mechanisms marshaled to fight infection, were more than doubled in runners after the high-
fat diet, compared to the low-fat regimen. Levels of PGE2, inflammation-causing
prostaglandins, increased after the endurance test and were higher when the runners were on
the low-fat diet. ... "

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--
Matti Narkia