Women who rode their bikes for at least 4 hours per week were 30% less likely to have gained weight than were women who did not bicycle, according to a large, 16-year follow-up study.
Even among women who didn’t ride a bike at the start of the study period but picked it up in the study’s final year, “less weight gain was seen even for 5 min/day or less increase in bicycling,” wrote Anne C. Lusk, Ph.D., in the June 28 issue of the Archives of Internal Medicine.
Dr. Lusk, a research fellow in the department of nutrition at the Harvard School of Public Health, Boston, took a sample of women from the Nurses’ Health Study II, which began in 1989. Originally, it included 116,608 U.S. female nurses aged 25-42 years who responded to a mailed questionnaire about their medical history and lifestyle.
Dr. Lusk and her colleagues included only women who were still premenopausal in 2005 and excluded women who were pregnant or lactating or who had been pregnant or lactating within 12 months. They also excluded women who reported extreme weights or body mass indexes (BMIs), extreme weight changes, chronic conditions, and those who simply did not report their physical activity.
After those exclusions, the analysis included 18,414 healthy premenopausal women.
In both 1989 and 2005, women in the studies were asked to report whether they participated in any of 10 physical activities, including walking, biking, and other forms of exercise. The women then estimated how many hours per week they spent doing each exercise and, for walking, what percentage of it was “brisk,” compared with “slow.”
The researchers also asked about total time “sitting at home,” such as watching television, reading, eating, or doing other sedentary activities.
“Because inactivity and, in particular, TV watching have been associated with obesity, which might confound the associations with [physical activity], total sitting at home was included in our models,” they wrote (Arch. Intern. Med. 2010;170:1050-6).
Between 1989 and 2005, Dr. Lusk found that the study participants gained an average of 9.3 kg. Leaner women, with a BMI of less than 25 kg/m2, gained a mean of 8.4 kg, while women with a BMI greater than 25 gained a mean of 12.6 kg.
Controlling for baseline activity and other risk factors, an increase of 30 minutes per day in total physical activity between 1989 and 2005 was associated with less weight gain, with an average loss of 1.31 kg. In contrast, an increase of 30 minutes per day in total time sitting at home was associated with greater weight gain, with an average increase of 0.21 kg.
More specifically, bike riding was associated with an average weight loss of 1.59 kg, compared with an average weight gain of 0.06 kg associated with slow walking, a statistically significant difference.
However, brisk walking still resulted in the greatest average weight loss, 1.81 kg.
After controlling for participants’ baseline ages, bike-riding habits, and weight, the researchers found that women who engaged in bicycling 4 hours per week or more were less likely to gain weight between 1989 and 2005 (odds ratio 0.71), compared with women who did not ride their bikes in 2005.
In addition, “There was a significant inverse dose-response relationship between increased time spent bicycling in 2005 and odds of weight gain,” wrote Dr. Lusk. Women with greater weight at baseline in 1989 experienced even better results than women with lower baseline weights.
Although research comparing bicycle riding with brisk walking is “relatively new,” Dr. Lusk and her colleagues stated that the date show that bike riding has real health benefits.
In the United States, however, 9% of the population walks for commuting, while 0.5% of people commute by bicycle, the researchers noted.
“Unlike discretionary gym time, bicycling could replace time spent in a car for necessary travel of some distance to work, shops, or school as activities of daily living,” they wrote. “Bicycling could then be an unconscious form of exercise, because the trip’s destination, and not the exercise, could be the goal.”
Dr. Lusk and her colleagues reported no financial disclosures in relation to the study. Dr. Lusk and one other colleague have received grants from the U.S. National Institutes of Health. The Nurses Health Study II was supported by a grant from the U.S. National Cancer Institute.
Copyright (c) 2009 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
一项为期16年的大规模随访研究显示，每周骑单车至少4 h的女性体重增加的可能性比不骑的女性低30%。
Anne C. Lusk博士在6月28日出版的《内科学纪要》(Archives of Internal Medicine)上指出，甚至在研究开始时不骑单车但在研究最后1年才骑的女性中，“即使每天多骑≤5 min也有助于降低体重。”
波士顿哈佛大学公共卫生学院营养系的研究员Lusk博士从护士健康研究II(该研究开始于1989年)中抽取女性样本。该研究通过向受试者邮寄有关病史和生活方式的问卷来进行调查，并最初入选116,608名美国女护士(年龄为25~42岁)。
Lusk博士及其同事仅纳入2005年时仍未绝经的女性，并排除妊娠或哺乳的女性或在12个月内妊娠或哺乳的女性。他们还排除报告极端体重或体重指数(BMI)、极端体重改变、慢性疾病的女性和那些根本未报告体力活动情况的女性。
在进行这些排除后，共18,414名健康的绝经前女性被纳入分析。
在1989年和2005年，要求研究中的女性报告自己是否参加10项体力活动中的任何一项，包括步行、骑单车和其他形式的运动。这些女性随后估计自己每周花在每项运动上的小时数；在步行方面，估计“快速”步行与“慢速”步行各占多少比重。
研究者还询问“坐在家里”(如看电视、阅读、吃饭或其他久坐行为)的总时间。
他们写道：“由于不活动，尤其是看电视与肥胖相关，这可能会混淆(肥胖)与体力活动之间的关联，因此我们的模型中包括了坐在家里的总时间。”(Arch. Intern. Med. 2010;170:1050-6)
Lusk发现，受试者体重在 1989~2005年间平均增加了9.3 kg。BMI<25 kg/m2的苗条女性体重平均增加8.4 kg，而BMI>25 kg/m2的女性体重平均增加12.6 kg。
对基线活动和其他危险因素进行校正后发现，在1989~2005年这段时间内，每天总体力活动时间增加30min与体重降低相关(平均降低1.31 kg)。相反，每天坐在家里的总时间增加30min与体重增加相关(平均增加0.21 kg)。
更具体而言，骑单车与体重平均降低1.59 kg相关，而慢速步行与体重平均增加0.06 kg相关，差异具有统计学意义。
但快速步行使体重平均降低最多(1.81 kg)。
研究者在对受试者的基线年龄、骑单车习惯和体重进行校正后发现，在1989~2005年这段时间内每周骑单车≥4 h的女性体重增加的可能性低于2005年时未骑单车的女性(比值比0.71)。
此外，Lusk博士写道：“2005年时骑单车时间增加与体重增加的可能性之间存在显著剂量反应负相关”，并且1989年时基线体重较重的女性的结果甚至优于基线体重较轻的女性。
Lusk博士及其同事表示，尽管比较骑单车与快速步行的研究“相对较新”，但数据表明骑单车对健康具有实际益处。
不过，研究者指出，在美国约9%的人通过步行方式上下班，而仅有0.5%的人通过骑单车方式上下班。
他们写道：“与需要抽时间上健身馆不同，骑单车可作为日常活动，代替汽车去到一定路程之外的工作场所、商店或学校。由于在这些情况下我们通常在乎的是行程的目的地，而非运动本身，因此骑单车是一项不知不觉就可以完成的运动。”
Lusk 博士及其同事声明没有任何与该研究相关的经济利益冲突，但她与1位同事从美国国立卫生研究院获得资助。该护士健康研究II获得美国国立癌症研究所的资金支持。
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