High Fat or High Carb? (Read 1417 times)

For reasons that are unclear, high fat diets seem to preserve muscle glycogen levels in endurance exercise. Depletion of muscle glycogen levels causes fatigue in endurance sports. An interesting "spanner" that can be thrown in to the works here, is a study performed last year (Med.Sci.Sport & Exerc.30:456-461,1998) on untrained males tested in aerobic endurance (in this case, running). One group was fed a diet higher in fat (62% of total calories) and another group was fed a high carbohydrate (65% of total cals) diet. After four weeks on the diets the subjects ran at 80% of VO2 max until exhaustion. Now according to some nutritionists, that sort of fat intake could not possibly allow for optimal muscle glycogen reserves and thus result in poor performance. Theoretically, untrained subjects would not utilize fat as a fuel very effectively either. However, the results of this study show this was not the case. There no difference in time running to exhaustion between the high fat group and the high carb group. A lot of endurance athletes and the coaches/nutritionists that look after them are real big on high carb diets and frown upon anything (such as fat) that may impede glycogen accumulation in muscle. I think high carb/low fat diets play havoc with insulin levels and this impedes glycogen resynthesis in muscle and does not enhance it. Athletes that eat diets higher in fat maintain steady state blood sugar and insulin levels. This provides more effective nutrient transport into cells and consistent blood sugar levels. This means better performance. To put it simply, I think there is merit to keeping fat intake at a normal level (20-35% of total calories) for endurance events. The type and timing of carbohydrates in the hours after exercise has much more effect on glycogen replenishment than the total amount consumed throughout the day.

Bad fat - saturated, hydrogenated.......

There is a great deal of interest in the training habits of the world's elite athletes. Of particular interest to all endurance athletes alike is that of Kenyan runners, since they have dominated the field of distance running for over a decade. [...] What is the Kenyan diet? A group of sport and nutrition experts led by Yannis Pitsiladis from the International Centre for East African Running Science based in Glasgow studied a group of ten elite Kenyan middle distance runners during their peak training season in 2004. Their diet was found to be very simple. The group of runners consumed five different meals spaced around two different running workouts. Interestingly, their food intake was primarily from vegetables, grains and starches (86%), such as bread, rice, potatoes, porridge, cabbage, kidney beans, and ugali (the national dish of Kenya composed of corn meal paste), and less so from meat (14%), which was mostly beef. Their fluid intake was sufficient at 2.3 liters per day; however, just over half of that fluid came from tea. The runners drank about 1.1 liters of water and 1.2 liters of tea per day. Basic, but rich! The Kenyan diet is so basic yet so sustainable. They rely on their agriculturally rich land to supply them with food for life and for sport. Further, unlike most westernized societies, the Kenyans are not presented with a superfluous amount of food choices and diet pressures everywhere they go. They rarely if ever consume candy, soda, or processed foods. They eat to survive and prosper rather than to indulge.

Unfortunately I have conclusive proof that all Kenyan athletes will die. [no-one talks about what the Kenyans may achieve if they had a slightly more balanced diet... don't forget that their diet as described above developed through necessity not choice. Nobody in Kenya regularly eats meat (apart from the politicians) as it is too scarce and too expensive.] Anyway, the evidence that I have seen suggests that they will die.

What about Coe¹s whine that British runners could transform themselves from joggers into champions if only they paid they mimicked the Kenyans. As the myth goes, Kenyans are great because they ran to school as kids and torture themselves in practice. That brings belly laughs from Wilson Kipketer, who destroyed Coe¹s long-held 800-metre record in 1997. "I lived right next door to school," he laughs. "I walked, nice and slow." The reality is that for every Kenyan monster-miler putting in 100-mile weeks, there are others, like Kipketer, who get along on less than thirty. ³Training regimens are as varied in Kenya as any where in the world,² notes Colm O¹Connell, coach at St. Patrick¹s Iten, the famous private school and running factory in the valley that turned out Kipketer and other Kenyan greats. O¹Connell eschews the mega-training so common among world champion wannabees in Britain and Europe. The explanation for African domination of running, it turns out, can be found mostly in the genes. ³Africans are naturally, genetically, more likely to have less body fat, which is a critical edge in elite running,² notes Joseph Graves, Jr., an African American evolutionary biologist at Arizona State University. "Evolution has shaped body types and in part athletic possibilities. Don¹t expect an Eskimo to show up on an NBA court or a Watusi to win the world weightlifting championship. Differences don¹t necessarily correlate with skin color, but rather with geography and climate. Genes play a major role in this.² Highly heritable characteristics such as skeletal structure, muscle fiber types, reflex capabilities, metabolic efficiency and lung capacity are not evenly distributed among populations and cannot be explained by known environmental factors. Though individual success is about opportunity and "fire in the belly," thousands of years of evolution have left a distinct footprint on the world's athletic map.

It will be years before the study, which began four years ago, determines how the diet affects lifespan. But John Holloszy and his collaborator Luigi Fontana have already found that those following such a calorie-restricted diet -- they call themselves "CRONies" (Caloric Restriction with Optimal Nutrition) -- are protected against some diseases associated with aging, such as cardiovascular disease and Type 2 diabetes. The researchers are now planning a larger trial, in which people eating an average diet will reduce their caloric intake by 25 percent, to determine how caloric restriction leads to biological changes over time.

High-Fat Diet Raises "Good Cholesterol" In Trained Runners [...] 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. "Liberalizing the fat content gives athletes more calories, and it certainly doesn't harm their health, like everyone thought," said John Leddy, M.D., associate director of the UB Sports Medicine Institute and primary author of the study. "We thought the cholesterol ratio would get worse, but LDL and total cholesterol didn't change, and HDL went up. The best thing happened that could have happened.