Fat has got a bad reputation. It appears to be fully deserved, but isn't.

Many of us can reach down to our waists (or thighs, in the case of women), and grab a handful of body-fat. We get confused because since this stuff is referred to as body-fat, it implies that it got there through eating too much dietary fat.

In response, and determined to do something about it, many people promptly decide to cut down on eating fat in their diet. Which, if you are a distance runner, may not be a good idea.

Distance running is fuelled by a mixture of carbohydrates (in the form of glucose and glycogen) and fats.

The precise blend of glycogen and fats used during exercise will depend upon the exercise intensity and the fitness of the subject.

Glycogen and fat stores are replenished through our diet. A diet that increases dietary fat without compromising glycogen stores has been shown in research to improve endurance performance in endur-ance athletes.

In addition, eating more fat increases fat burning for fuel, which in turn spares glycogen and makes it last longer. This is good news, for when the glycogen runs out, the runner stops.

Endurance performance is dependent upon both fitness of the runner and the available fuel stores.

It's simple, deplete your fuel stores and your race is effectively over.

Many runners believe that a low body weight is necessary for optimal performance and that fat intake is unhealthy anyway.

Therefore, a low fat intake has become the diet of choice for a number of athletes.

A four-week study of 12 males and 13 females sought to determine the effects of a low, medium and high fat diet on performance in experienced runners.

A range of food options were developed and each study group was assigned a diet of a low, medium or a high fat type, about 15 per cent, 30 per cent and 45 per cent of calories as fat, respectively.

Protein compositions of the diets were between 13 and 17 per cent.

The first thing to note was that none of the diets changed the body weight or per cent body fat of the subjects.

All the diets were isocaloric, meaning the total calorie intake from each diet was the same.

Increasing your total calorie intake to meet the demands of exercise does not cause a weight gain. Only when you eat more calories than you burn will weight gain occur.

Another interesting note was that runners on the low fat diet ate 19 per cent fewer calories than on the medium or high fat diets.

The researchers believe that the blandness of the low-fat food (and fat is tasty), caused runners on that diet to voluntarily eat less.

Low-fat food is not very appetising. The good news is that the endurance times of the subjects on the medium fat diet increased 20 per cent in females and 8 per cent in males compared to the low fat diet.

So, runners could run harder, longer on 30 per cent fat diet compared to the 15 per cent diet.

Little difference

There was no significant difference in endurance time between the high and medium fat diets. So eating more than approximately 30 per cent fat did not lead to even greater endurance.

Now one potential risk of increasing the fat content of the diet by reducing carbohydrate content is compromised by muscle glycogen stores. So do not take this study as an excuse to consume more fat in your diet at the expense of carbohydrate.

Carbohydrate should still make up approximately 55 per cent of your fuel intake.

This study does demonstrate that eating 30 per cent dietary fat intake without compromising carbohydrate intake improves endurance performance.

A word of warning: if the diet is low in total calories, increasing fat and decreasing carbohydrates will reduce glycogen stores and leads to poorer performance.

Reducing total calories and/or fat will not lead to optimal exercise performance. The intramuscular stores of glycogen and fats are the crucial ones.

Conclusion

These results suggest that runners on a low fat diet will tend to eat less and have reduced endurance performance than they would on a medium fat diet.

Best wishes to all runners in 2007 (including lots of PBs) from the Malta Marathon Organising Committee.

johnwalsh42195@yahoo.it