Fats

The second primary nutrient is fat. Like carbohydrates, fats provide energy (nine calories per gram). However, fats also serve a variety of other functions in the body. These functions include (1) offering protection for the other tissues (i.e. the major organs of the body), (2) allowing insulation from the cold, (3) storing the fat-soluble vitamins, and (4) comprising the major structural component of cell walls.

Fats can be classified as (1) saturated, (2) poly-unsaturated or (3) mono-unsaturated. The saturation of each type of fat is based on the number of hydrogen ions attached to the fat molecule. Saturated fats have the most hydrogen ions attached, the poly-unsaturated fats have less, and the mono-unsaturated fats have the least hydrogen ions.

Saturated fats are the least healthy of the three types of fats and are characterized by remaining solid at room temperature. Common examples include lard and butter. Even though this type of fat is the least healthy, it is still required by the body in small amounts and therefore should not be totally eliminated from the diet.

Poly-unsaturated fat is healthier than saturated fat and is characterized by being semi-solid at room temperature. Many of today’s margarines and butter alternatives are made with poly-unsaturated fats and thus require refrigeration.

Mono-unsaturated fat is the healthiest of the fats and remains liquid at room temperature. Examples of mono-unsaturated fats include most natural oils, such as olive oil.

Food items that contain mono-unsaturated fats but have been hydrogenated (meaning that hydrogen ions have been added) are less healthy than non-hydrogenated fats. One must be careful to read the ingredients of each food eaten to watch for mono-unsaturated fats that have been hydrogenated called partially hydrogenated oils.

Shortly, food labels in the US will also list these “transfats” in the food item which will help us avoid this potentially unhealthy type of “hydrogenated” fat.

Experts recommend that distance runners obtain 20 to 30 percent of their daily calories from fats. In addition, approximately one-third of one’s fat calories should come from each type of fat (saturated, poly-unsaturated and mono-unsaturated).

All excess fat in the diet will be stored as adipose (fat) tissue, which increases “dead” body weight and decreases performance. Examples of foods containing significant amounts of fats are lard, butter, meats, some dairy products and most varieties of oils.

Fats should be avoided prior to a race or hard workout. Fats are slow to empty from the stomach and may cause cramps, due to the decreased blood flow to the stomach which occurs during running.

Protein

The third primary nutrient is protein. Experts can’t agree but the ranges recommended are from 10 to 30 percent of their daily calories from protein for runners. The average American eats two to three times the protein requirement each day but finicky runners (and those who break down easy from hard training) may need to focus on their protein intake.

Proteins are composed of small substances called amino acids. They function as the major component of every structure in the body and also provide four calories of energy per gram, though you hope that you don’t regularly have to ‘burn’ protein for energy.

As a result of training and racing, our muscles and tendons experience small tears or micro-traumas which are repaired by the protein in our diet. This fact is why we even see a renewed focus on adding some protein to the traditionally carbohydrate-loaded recovery drinks. Some athletes even find that supplementing with protein powder aids their recovery. Excessive protein in the diet places great strain on the kidneys so there’s no need to eat like a body builder. Meats, beans and nuts are common examples of foods which contain significant amounts of protein.

脂肪

第二種主要營養(yǎng)素是脂肪。和碳水化合物一樣，脂肪也能提供能量（每克9卡），但是脂肪同時在體能還有其他功能。這些功能包括（1）為組織（比如身體的主要器官）提供保護；（2）隔離寒冷；（3）儲存脂溶性維生素；（4）細胞壁的主要結(jié)構(gòu)組成物。

脂肪可以分為（1）飽和脂肪酸（2）多不飽和脂肪酸（3）單不飽和脂肪酸。每種脂肪酸的飽和程度是基于脂肪分子上的氫原子數(shù)量而劃分的。飽和脂肪酸上的氫原子最多，多不飽和脂肪酸要少一些，而單不飽和脂肪酸的氫原子最少。飽和脂肪酸是三種脂肪中最不健康的，在室溫下保持固態(tài)，包括豬油和黃油。盡管這種脂肪最不健康，身體依然需要少量，因此不能從飲食中完全去除。

多不飽和脂肪酸比不飽和脂肪酸要健康一些，在室溫下保持半固態(tài)。現(xiàn)在許多人造奶油和黃油都是用多不飽和脂肪酸做的，因此需要冷凍保藏。

單不飽和脂肪酸是最健康的脂肪，在室溫下保持液態(tài)。常見的包括植物油如橄欖油。

那些包含單不飽和脂肪酸但是被氫化（添加氫原子）的食物比沒有氫化的要不健康。每種食物的成分都必須認真看看，是不是氫化的單不飽和脂肪酸，也就是所謂的部分氫化油。

最近，美國食品標簽上同時列出了“反式脂肪酸”，這有助于幫助我們避免可能存在的不健康的氫化脂肪。

專揀建議在長跑選手每日攝取的熱量中應當有20-30%來自脂肪。同時來自每種脂肪（飽和、多不飽和和單不飽和）的熱量應該大致各占1/3。

飲食中額外的脂肪都將儲存為脂肪組織，也就是為增加身體的死重量，降低跑步水平。含有很多脂肪的食物包括豬油、奶油、肉、一些乳制品和絕大多數(shù)各種油。

在比賽或強度訓練前要避免攝入脂肪。脂肪很難從胃中排空，這會在跑步中由于流向胃的血液減少而導致胃痙攣。
蛋白質(zhì)

第三種主要營養(yǎng)素是蛋白質(zhì)。專家推薦跑步者每日攝取的熱量應當有10-30%來自蛋白質(zhì)。美國人每天平均攝入的蛋白質(zhì)超過需要的2-3倍，但是講究的跑步者（以及那些很容易在強度訓練中放棄的跑步者）需要注意他們攝入的蛋白質(zhì)量。

蛋白質(zhì)是由氨基酸小分子組成的，他們是身體中所有器官的主要組成物質(zhì)，同時每克可以提供4卡的熱量，即使你并不希望依靠燃燒蛋白質(zhì)來獲得能量。

在訓練和比賽之后，我們的肌肉和肌腱會出現(xiàn)小疲勞或微創(chuàng)傷，這就需要我們飲食中的蛋白質(zhì)。這就是為何我們發(fā)現(xiàn)在傳統(tǒng)的以碳水化合物為基礎(chǔ)的恢復性飲料中又開始強調(diào)加入蛋白質(zhì)。一些運動員甚至發(fā)現(xiàn)補充蛋白粉可以有助于他們恢復。飲食中過量的蛋白質(zhì)會對腎產(chǎn)生很大的壓力，因此不必攝入像在身體發(fā)育階段那樣多的蛋白質(zhì)。肉、豆類和堅果是常見的富含蛋白質(zhì)的