作者：Deborah Brauser 齣處：WebMD醫學新聞 　　September 11, 2009 — 根據綫上發錶於6月15日Hepatology期刊的一篇小型隨機研究結果 久坐不動的肥胖者 有氧運動可能會降低脂肪肝的風險 - 趣味新聞網

發表日期 2009-09-26T08:24:11+08:00

     本帖最後由 lsc0019 於 2009-9-26 23:49 編輯

作者：Deborah Brauser
齣處：WebMD醫學新聞

September 11, 2009 — 根據綫上發錶於6月15日Hepatology期刊的一篇小型隨機研究結果，久坐不動的肥胖者可以藉由規律的體能活動降低非酒精性脂肪肝(nonalcoholic fatty liver disease，NAFLD)的風險。

此外，降低的風險並不因減輕的體重而定，而是增加運動計畫的直接結果。

澳洲雪梨大學肥胖、營養暨運動研究中心與運動暨運動科學科的Nathan A. Johnson等人寫道，這些資料第一次提供瞭規律有氧運動降低肥胖者肝脂肪的直接證據，即使體重未減輕。

研究作者指齣，體能活動對於脂肪肝的控製相當重要。

作者們指齣，身體脂肪的位置，特彆是內髒脂肪組織(visceral adipose tissue，VAT)，對於過度肥胖者的代謝與心血管後遺癥的重要性越來越受重視。

此外，新證據指齣，肝細胞過度儲存三酸甘油脂是肥胖的常見特徵，肝髒脂肪變性(或NAFLD)可能影響瞭約30%的成人族群以及大多數的肥胖者。

不過，有關飲食與運動介入對於降低肝髒三酸甘油脂濃度(HTGC)效果的證據很少，也沒有明確的藥物治療方法。

【需要針對減重之外的其他策略】
研究作者寫道，雖然有針對減重的介入方式，但藉由飲食控製而減輕的體重一般隻屬中等，對於生活型態調整來說，也逐漸被認為無法維持結果。因此，需要降低HTGC的適當治療策略，而不是隻針對減輕體重。

雖然有氧運動對於脂肪肝的效果尚未與體重減輕之間釐清，研究者試圖在本研究中評估其對於肝髒、血液、腹部與肌肉脂肪的效果。

Johnson醫師等人納入瞭23名肥胖、身體質量指數30 kg/m2或以上，且自我報告之生活型態屬於久坐不動者，飲酒量低(0-20 剋/天)的成人。進行一些基本測量以確認HTGC與飽和指數、腹部VAT以及皮下脂肪(SAT)區域和體積、肌肉細胞內三酸甘油脂濃度、心肺適能、人體測量、血液生化檢查等。

總共有19名病患被隨機分派接受4週受監督的有氧運動訓練(n= 12人)，包括每週3次腳踏車測功計課程(每次30-45分鍾)、或4週的假裝介入課程(安慰劑組、n= 7人)。安慰劑組的人在治療開始時接受1次受監督的伸展運動，之後直接在傢進行每週3次的伸展運動。

研究者以非侵犯性質子磁共振光譜法測量HTGC，以磁振造影測量腹部脂肪。在腳踏車測功計上測量體力勞動能力來評估心肺適能。兩組的所有測量都在完成分派的運動計畫後重復進行。

4週的有氧腳踏車運動之後，VAT容量顯著降低達12% (P< .01)，HTGC降低達21% (P< .05)。

有氧運動對於血漿的遊離脂肪酸也有顯著的降低(14%) (P< .05)。

運動訓練並未改變體重、股外側肌肌肉內三酸甘油脂、腹部SAT體積、磁振光譜測量脂肝髒脂肪飽和度、或胰島素阻抗性的體內平衡模式(P> .05)。

【第一次的直接證據】
研究作者寫道，對原本久坐不動的肥胖成人進行短期的有氧腳踏車訓練介入，提供瞭首次的直接實驗證據顯示，規律的有氧運動訓練降低瞭肝髒脂肪，不過，未同時改變體重或腹部SAT量。因此，規律運動可以緩和肥胖之代謝和心血管後遺癥，包括脂肪肝。

研究作者結論錶示，我們的觀察發現規律運動本身的健康助益，應可重新為那些有關體能活動對於預防和控製肥胖與NAFLD的爭論、甚至政策定調。換句話說，體能活動相當有助於脂肪肝的控製。

雪梨大學、澳洲國傢健康與醫學研究委員會支持本研究，Robert W. Storr 遺贈予雪梨大學之捐款給與研究作者之一。研究作者宣告沒有相關財務關係。

Aerobic Exercise May Reduce Risk for Fatty Liver Disease

By Deborah Brauser
Medscape Medical News

September 11, 2009 — Obese individuals with a sedentary lifestyle can lower their risk for nonalcoholic fatty liver disease (NAFLD) by engaging in routine physical activities, according to results of a small randomized study published online June 15 in Hepatology.

In addition, this lower risk was not contingent upon weight loss, but was a direct result of the increased exercise program.

"These data provide the first direct experimental evidence demonstrating that regular aerobic exercise reduces hepatic lipids in obesity even in the absence of body-weight reduction," write Nathan A. Johnson, from the Discipline of Exercise and Sport Science and the Institute of Obesity, Nutrition and Exercise at the University of Sydney in Australia, and colleagues.

"Physical activity should be strongly promoted for the management of fatty liver," add the study authors.

The location of body fatness, particularly visceral adipose tissue (VAT), is increasingly recognized as being of greater importance in determining the metabolic and cardiovascular consequences of excess adiposity, the authors report.

In addition, evidence is emerging that excessive storage of hepatocellular triglyceride is a common feature of obesity, with hepatic steatosis (or NAFLD) possibly affecting 30% of the adult population and the majority of obese individuals.

However, there is a paucity of evidence regarding the effects of diet and exercise interventions on reducing hepatic triglyceride concentration (HTGC), and no definitive pharmacotherapy exists for it.

Strategies Besides Those Aimed at Weight Loss Are Needed

"Although intervention aimed at weight loss is advocated, reductions in weight by dietary restriction are typically modest and are increasingly viewed as an unsustainable outcome of lifestyle modification," write the study authors. "Therefore, appropriate therapeutic strategies for reducing HTGC, which are not contingent upon weight loss, are needed."

Although the effect of aerobic exercise on liver fat independent of weight loss has not been clarified, the investigators sought to assess its effect on hepatic, blood, abdominal, and muscle lipids for this study.

Dr. Johnson and his team enrolled 23 obese adults who had a body mass index of 30?kg/m2 or higher and who reported a sedentary lifestyle and low alcohol intake (0-20?g/day).

Baseline measurements were performed to determine HTGC and saturation index, abdominal VAT and subcutaneous adipose tissue (SAT) area and volume, intramyocellular triglyceride concentration, cardiorespiratory fitness, anthropometry, and blood biochemistry.

A total of 19 patients were then randomly allocated to receive either 4 weeks of supervised aerobic exercise training (n?= 12) made up of 3 cycle ergometer sessions (30–45 minutes each) per week or 4 weeks of a sham intervention (placebo, n?= 7). Those in the placebo group received 1 supervised stretching session at treatment initiation and were then directed to perform the stretches 3 times per week at home.

The investigators measured HTGC with noninvasive proton magnetic resonance spectroscopy and measured abdominal lipids by magnetic resonance imaging. Cardiorespiratory fitness was assessed using the Physical Work Capacity test undertaken on a cycle ergometer. All measurements for both groups were repeated at completion of the allocated exercise programs.

After 4 weeks of aerobic cycling exercise, VAT volume was significantly reduced by 12% (P?< .01) and HTGC was reduced by 21% (P?< .05).

The aerobic exercise regime was also associated with a significant (14%) reduction in plasma free fatty acids (P?< .05).

Exercise training did not alter body weight, vastus lateralis intramyocellular triglyceride, abdominal SAT volume, magnetic resonance spectroscopy-measured hepatic lipid saturation, or homeostasis model assessment of insulin resistance (P?> .05).

First Direct Evidence

"Using a short-term aerobic cycling training intervention in previously sedentary obese adults, we provide the first direct experimental evidence demonstrating that regular aerobic exercise training reduces hepatic lipids without concurrent changes in body weight or abdominal SAT content," write the study authors. "Thus, regular exercise may mitigate the metabolic and cardiovascular consequences of obesity, including fatty liver."

"Our observation of a beneficial effect of regular exercise itself?.?.?. should refocus the debate, and hence policy, on the role of physical activity in the prevention and management of obesity and NAFLD. In other words, physical activity should be strongly promoted for the management of fatty liver," conclude the study authors.

This study was supported by the University of Sydney, along with a program grant from the Australian National Health and Medical Research Council and the Robert W. Storr bequest to the University of Sydney given to one of the study authors. The study authors have disclosed no relevant financial relationships.

Hepatology. 2009;50:000-000.

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