For people with a normal BMI, the spectrum of PA or scheduled exercise options is almost unlimited and is largely dependent upon interest, skill, time, and financial resources. For the obese patient, another factor that influences participation in PA is the patient's weight and ability to move without injury. It is not uncommon for patients to lose weight through dietary means before increasing their LTPA. When obese patients begin to consider PA as an important component of their obesity treatment program, walking can be a fundamental component of that program for both scientific and practical reasons.
From a scientific perspective, Gregg et al. reported a dose-response rate in the relationship between walking and mortality among US adults. The study involved 2896 adults with diabetes. Weekly duration of walking was the key factor in reducing mortality. Those who walked 2 hours per week had a 39% lower all-cause mortality rate and a 34% lower cardiovascular (CVD) mortality rate. The relative risk for both all-cause and CVD mortality was lower for those who walked 3 to 4 hours per week (56% and 53%). The protective relationship of walking to all-cause mortality and CVD was the same for both genders, all adult ages, race, BMI, duration of diabetes, comorbid conditions, and limitations .
Similar positive health benefits from walking were found in postmenopausal women, with a lower risk of hip fractures by 6% for each hourly increase in walking per week , and in premenopausal women who maintained weight loss and decreased waist circumference with walking 2 to 3 hours per week .
How does walking impact the ability to lose weight or maintain weight loss? Is it a dose-response relationship? In a 12-week study by Jakicic et al., 184 sedentary women were divided into four groups of various physical intensity and duration levels. During follow-up at 12 months, women who reported walking <150 minutes/week maintained a mean weight loss of 4.7%, whereas those who walked for >150 minutes per week had a mean of 9.5% . The majority of participants in the National Weight Control Registry (NWCR) report they typically exercise 1 hour per day  compared to the Surgeon General's recommendations of cumulative moderate-intensity exercise no less than 30 minutes per day, 5 days per week . The International Association for the Study of Obesity in 2003 stated in its consensus statement that to prevent weight gain or regain a person should experience moderately intense activity 45 to 60 minutes per day .
However, some data suggest that for some patients PA does not have a dose-response relationship, and that PA is not more effective than diet alone . Though 91% of the NWCR participants describe exercising on a regular basis, 9% do not exercise yet still maintain their weight loss . For the physically handicapped or those who dislike physical activity, this means the possibility still exists to lose weight and to keep it off, though the probability of weight loss may be less compared to those who are active on a regular basis. Also, for many obese patients, walking is the only safe PA possible until some weight is lost.
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