脂肪是耐力的燃料嗎?!

為了恭賀施總當上本屆會長，也證明永和慢跑人才濟濟與接力棒棒相傳，小弟不惜甘冒在眾多位博士面前獻醜，翻譯一篇在Runner’s World網站上刊登的文章來當作施會長的賀禮。(施會長，禮輕情意重，還請包含笑納)。

HowHow 敬上


脂肪是耐力的燃料嗎?!
里斯-愛波蓋特 博士

信不信由你，太過沉迷於節制脂肪的攝取將導致健康受損而且不利於你的競賽成績。很多人懼怕攝取脂肪，就拿我的跑步夥伴艾倫來說，最近有次在午餐中我注意到他點沙拉時不加沙拉醬，而且拒絕在他的義大利麵上灑一些胡桃，而要求額外的麵包來取而代之。他的說法是他為了跑步及心臟健康而儘可能的避免脂肪攝取。

他就像百分之六十的美國人一樣，把避免脂肪攝取當作是營養健康的第一順位，然而問題是，這些出自好意的太過沉迷於節制脂肪的攝取在許多方面上是潛在的傷害你的健康。

當然了，吃一大堆像漢堡和薯條這些油玆玆的食物確實會增加心臟病的危險，但是許多人卻沒有補充足夠的良性脂肪，這會造成在你血液中使你動脈血管阻塞(如李X輝先生)的三酸甘油脂的含量升高，一味遵循低脂肪的節食食譜將使你心情喜怒無常及悶悶不樂，而且新的證據顯示這會影響你比賽成績的表現。

脂肪的真相

從許多方面來說其實脂肪是好的，撇開那些食物更顯美味及使你有飽足感不說，脂肪就像維他命及礦物質一樣的重要，特別是一些稱作亞美加-6(Omega-6)及亞美加-3(Omega-3)的脂肪酸對一個常人的健全免疫系統、皮膚健康及神經纖維非常重要(而這些脂肪酸可在核桃類、蔬菜油、亞麻籽及魚中這些食物中補充攝取)。研究指出我們早期祖先攝取這些亞美加酸比我們今日現代人多，而另一方面今日現代人，卻從動物類食物與加工食品中，攝取大量的飽和脂肪及氫化脂肪；這些現代化的食物卻幾乎沒有提供任何，特別像是亞美加-3s重要維生的脂肪酸；其結果是一狗票的慢性疾病將發展為自身免疫病如心臟病、癌症、多發性硬化症及像牛皮癬之類的皮膚病，而這些疾病在幾千年前是不存在的。

然而這些亞美加脂肪酸的攝取比例也是非常重要的，太多的亞美加-6脂肪酸及太少的亞美加-3s脂肪酸將導致脆弱的免疫系統並弱化神經纖維，但不幸的是沒人精確知道一個人應攝取多少量，但是專家們一致同意增加魚類、亞麻籽類(粗磨粉或榨成的油)及核桃類的攝取是對的。

脂肪與你的心臟

研究顯示只要你全部攝取的熱量中來自脂肪中，大部份有百分之四十的單不飽和脂肪(像是橄欖油)就能降低膽固醇濃度和心臟病危險；令一方面，若能避免飽和脂肪及過飽和脂肪(常存在於如油炸過的加工食品)的攝取，也能夠幫助你的動脈暢通。

美國心臟協會(AHA)現在建議脂肪攝取不要超過一天攝取的總熱量的百分之三十(大約是一天65公克)，而這些攝取的脂肪中不要超過百分之十是來自飽和脂肪(大約是一天最多約20公克)。然而有些健康專家卻提倡較上述更為嚴格的脂肪攝取，如著名的心臟病學家與節食食譜作家的醫學博士迪恩-歐爾尼西說，他建議他的病人一天脂肪的攝取量為一天攝取總熱量的百分之十，如此可避免他的病人動脈進一步的傷害並且幫助治療已經栓塞的動脈。

但是在美國心臟協會最近發表的聲明裡指出，這些節食食譜並非適用於任何人，博士迪恩-歐爾尼西與其他提倡低脂飲食的人，要求你接受的是一整套的完整規劃，其中包括定期運動、減壓及其他飲食的改變，如吃較多的水果與蔬菜；也許這些綜合因素就是動脈不栓塞的原因而非僅僅是低脂飲食的緣故。況且在一些各案中，低脂但高碳水化合物的飲食容易增加三酸甘油脂的濃度，也就是同時也降低了對心臟有益的高密度膽固醇(HDL)濃度。

一個極端的低脂節食將會使你心情鬱卒，英國Sheffield大學的營養系與精神學系的研究報告指出，如果人降低百分之四十到二十五的脂肪攝取量將會使憤怒與敵意增加，學者推測這是飲食中太少的脂肪將會改變腦內控制心情與行為的化學變化。

使你跑的更快的脂肪

況且除了保持健康外，正確的脂肪與其適當的攝取量還能幫助跑步的表現，不要誤會，我不是叫大家拋棄碳水化合物；攝取豐富的碳水化合物使我們肌肉裡的肝醣儲存豐富，而肝醣儲存量對耐力表現是非常重要的；但是脂肪也是長距離跑步與其他耐力賽中重要的燃料。學者早已注意到耐力訓練使你肌肉習於轉換脂肪成為燃料，水牛城紐約州立大學一部份的研究建議跑者的飲食中脂肪攝取應佔百分之三十比佔百分之二十的飲食有意義。

在這些研究中有一份研究，實驗對象是給一群每週里程數在64公里以上的跑者吃四個星期的百分之十七脂肪含量的餐飲，其後另外再吃四個星期的百分之三十二脂肪含量的餐飲，每一個階段結束後，參與者將在跑步機上測驗跑到力竭為止。

其結果是吃適當脂肪含量餐飲比吃低脂含量餐飲，在距離上男生可以多跑百分之二十四，女生可以多跑百分之十九。有限的研究報告也同樣證明在耐力上訓練有素的運動員在轉換較高脂肪含量的飲食攝取一個星期或更多後，其耐力會增加；但我並非建議在馬拉松比賽之前脂肪攝取比碳水化合物攝取重要，而是平常攝取適量且正確的脂肪可以保證你在長距離跑步中有適當的脂肪儲存量。

你的脂肪攝取計劃

建立在眾多的研究報告與美國心臟協會建議，你應攝取佔總熱量百分之三十的脂肪，然而攝取脂肪量遠不及你攝取脂肪的種類重要，這裡提供你如何攝取正確脂肪的例子；烹飪時以橄欖油及菜籽油取代人造奶油與奶油，一週至少吃85公克到255公克的魚肉，多常常在你的加榖類片牛奶、優格或沙拉上灑一些胡桃、杏仁或其他的堅果類；加一些亞麻籽仁或亞麻籽油在你的餐飲上。(這對老中來說還真難啊!難怪老外比較不容易腦中風)，避免吃含氫化脂肪(過飽和脂肪的組成物)如炸馬鈴薯條、炸洋芋片及餅乾。選擇全榖類製品比精緻榖類製品更能攝取少量重要的脂肪，每天四到五份的水果與蔬菜，一開始好像聽起來很多但是你最後會感到很飽滿而且因此容易拒絕零食與甜食的誘惑。

以下為原文

Fats As Fuel?
by Liz Applegate, Ph.D.

Believe it or not. The obsessive skimping on fat could be harmful to health--and detrimental to your running performance as well
Many people fear fat. Take my running buddy, Alan. At a recent lunch, I noticed that he opted for salad without dressing. He also declined a sprinkling of walnuts over his pasta, asking instead for extra bread. "I cut out added fat whenever I can," he said, citing his running and heart health as reasons.

He's one of the 60 percent of Americans who rank fat-cutting as their number-one nutritional concern. Problem is, this obsessive skimping on fat, while well-intentioned, is potentially harmful on a number of fronts.

Sure, eating lots of food oozing with fat, such as burgers and fries, does boost heart-disease risk. Yet some people don't get enough fat. This can make matters worse by driving up their levels of artery-clogging circulating fats (triglycerides). Following rigid low-fat diets may also contribute to moodiness and depression and, new evidence suggests, may even hurt your racing performance.

The big fat truth
In many ways, fat is good. Besides tasting great and helping you feel full, fat is just as important as vitamins and minerals. Special essential fats, called omega-6 and omega-3 fatty acids (found in nuts, vegetable oils, flaxseed and fish), are crucial for a strong immune system and healthy skin and nerve fibers.
Research suggests that our early ancestors ate much more of these omega fats than we do. Today, on the other hand, we eat mostly saturated and hydrogenated fats from animal foods and processed snacks. These modern-day foods provide hardly any essential fatty acids, particularly omega-3s. As a result, an array of chronic ailments may have developed-auto-immune diseases, heart disease, some cancers, multiple sclerosis and skin conditions (such as psoriasis)-most of which were nonexistent thousands of years ago.

Even the ratio of these omega fats is important. Too many omega-6 fats and too few omega-3s may contribute to a fragile immune system and weakened nerve fibers. While no one knows the exact amount of omega-3 and omega-6 fats you need for optimal health, researchers agree that upping your intake of fish, flaxseed (meal or oil) and nuts is a step in the right direction.

Fat and your heart
Getting up to 40 percent of your total calories from fat-as long as it's mostly monounsaturated fat, such as olive oil-can cut cholesterol levels and heart-disease risk, studies show. On the other hand, avoiding saturated fats and trans fats (found in processed foods) also helps keep your arteries clear.

The American Heart Association (AHA) currently recommends getting no more than 30 percent of your calories from fat (about 65 grams of total fat daily), with no more than 10 percent of those fat calories coming from saturated fats (roughly a 20-gram-per-day limit).

Some health professionals, however, advocate a much lower fat intake. Dean Ornish, M.D., famed cardiologist and diet-book author, says a diet with 10 percent fat protects his patients from further artery damage and helps heal those already-clogged arteries.

In a recently released statement, the AHA points out that these low-fat diets are not for everyone. For starters, Dr. Ornish and others who promote low-fat fare require you to accept a total package, which includes regular exercise, stress reduction and other dietary changes, such as eating more fruits and vegetables. It may be the combination of all these factors that's responsible for unclogging blocked arteries, not just the low-fat diet.

Also, for some individuals, a low-fat, high-carbohydrate diet tends to increase levels of triglycerides while lowering heart-healthy HDL cholesterol levels.

A very low-fat diet may also wreak havoc on your mood. In a study from the nutrition and psychiatry departments of the University of Sheffield in England, levels of anger and hostility increased in people who decreased the percentage of fat in their diet from 40 percent to 25 percent. Researchers suspect a diet that's too low in fat may alter the brain chemicals that control mood and behavior.

Fast fat
Besides keeping you healthy, the right fats in the right amounts may also keep you running. No, I'm not advising that you forsake carbohydrates. Eating carbohydrate-rich foods keeps muscle glycogen stores packed, and that's crucial for endurance performance. But fat is also a vital fuel source during long runs and other endurance efforts.

Researchers have long noted that endurance training turns your muscles into better fat-burners, and a handful of studies done at the State University of New York at Buffalo suggest a diet with 30 percent fat makes more sense for runners than diets with less than 20 percent.

In one of these studies, a group of runners who averaged 40-plus miles per week ate a diet with 17 percent fat for four weeks and then switched to a diet with 32 percent fat for another four weeks. At the end of each four-week segment, the participants ran to exhaustion during a treadmill test.

Result: The men ran 24 percent longer and the women 19 percent longer following the moderate-fat diet, compared to the low-fat one. A limited number of other studies have also shown improved endurance when already-trained endurance athletes switch to a higher fat intake for a week or more. I'm not suggesting that we "fat-load" rather than carbo-load before a marathon, but eating the right amount of fat all the time may ensure adequate fat stores for your long runs.

Your fat plan
Based on various studies and AHA recommendations, shoot for a diet that includes 30 percent of total calories from fat. The amount of fat, however, is much less important than the type. Here's how to focus on the right fats:
Use olive and canola oils when cooking, instead of margarine and butter.
Aim to eat at least 3 to 9 ounces of fish a week.
Use walnuts, almonds and other nuts more frequently as a topping for cereal, yogurt or salads.
Add ground flaxseed or flaxseed oil to your diet (try my flaxseed muffin recipe, left).
Avoid processed foods such as chips, crackers and other foods with hydrogenated fats (a source of trans fats). Select whole-grain products over refined versions for small amounts of essential fats. Include four to five servings of fruit and four to five servings of vegetables every day. This may sound like a lot at first, but you'll end up feeling more satisfied and will be less inclined to binge on empty sweets.