Physical Activity for Health and Weight Loss: How Much is Enough?

| February 11, 2011

by Alexis M. Peraino, MD

Financial Disclosure: Dr. Peraino reports no conflicts of interest relevant to the content of this article.

Dr. Peraino is a physician at Cedars Sinai Medical Center in the Department of Medicine and Center for Weight Loss and Assistant Clinical Professor Step I, David Geffen School of Medicine University of California, Los Angeles, California.

Abstract
Physical inactivity is a key component contributing to the obesity epidemic. Exercise and physical activity provide significant health benefits as well as aide in weight loss and weight maintenance. Modest physical activity guidelines have been published to help improve overall public health and to encourage patients to start exercising. Fitness benefits play a large role in reducing cardiac and all-cause mortality. In addressing obesity and its associated comorbidities, such as diabetes, physicians and healthcare professionals need to stress the importance of regular and consistent activity for both prevention and treatment.

Introduction
Lately, the media seems to be inundated with new, faster, and better ways to exercise and become fit. From sensationalized exercise sessions on NBC’s The Biggest Loser to The 90-Second Work Out found online, these extremes tend to muddy the waters in regard to what exercise and activity can do for one’s health and weight. Americans want the guaranteed weight loss and fitness quick fix, but unfortunately, the real work is not glitzy or glamorous. Weight loss and fitness require dedication to lifestyle changes: eating less and participating in regular physical activity.

According to the Centers for Disease Control and Prevention (CDC), approximately one third of Americans are obese.[1] Inactivity is an important part of the weight-gain equation, and the trends regarding lack of physical activity and the increasing rates of obesity show many parallels. Data from the Behavioral Risk Factor Surveillance System in 2005 demonstrated that less than 50 percent of the United States population participates in recommended levels of physical activity.

Approximately 15 percent of the population are inactive, participating in less than 10 minutes of activity per week.[2] The remainder of the population is insufficiently active, not meeting the recommendations for activity but doing more than 10 minutes of activity per week.[2] These data suggest that approximately 40 percent of Americans want to be active, but do not know how active they need to be in order to get health or fitness benefits. In October 2008, the United States Department of Health and Human Services (HHS) provided the first federal activity guidelines to help define what Americans need to do to be sufficiently active.[3] These guidelines are consistent with previous recommendations from the American College of Sports Medicine and American Heart Association,[4] and are modest in regard to the amount of physical activity needed for health and fitness benefits. The guidelines serve as a useful launching place for clinicians and healthcare providers to make an impact on moving patients out of the lowest levels of cardiorespiratory fitness as well as improving overall public health.

Benefits of Physical Activity
Many patients see the primary benefit of exercise and physical activity as weight loss, but really the benefits go well beyond weight loss. There is a misconception that if you are thin then you are fit; this could not be further from the truth. Myers et al[5] showed that relative risk of death from any cause in patients with cardiovascular risk factors was reduced among patients who reached an exercise capacity of at least five metabolic equivalents (METS). The Aerobics Center Longitudinal Study of Healthy Women[6] compared death rates of women who were overweight and obese and found that unfit women had a death rate more than double those of fit women. These studies strongly suggest that fitness is a stronger predictor of all-cause mortality and cardiovascular disease than is fatness. Small improvements in fitness, such as moving from sedentary to unsedentary, reap the largest health benefits.[7] Collectively, these studies and others suggest that improved fitness lowers cardiovascular death by a graded and inverse association with cardiovascular and all-cause mortality.[5,6,8,9] The well-defined benefits of regular activity include a reduction in all-cause mortality, heart disease, stroke, type 2 diabetes, hypertension, hyperlipidemia, metabolic syndrome, colon cancer, and breast cancer.[3] Other important benefits include reduced depression, reduced falls, and improved cognitive functioning.[3] It is important to note that lack of weight loss does not diminish these health benefits, but lack of consistency does. In this case, exercise is really a pill that you need to take daily or the benefits will fade away.

The use of exercise and activity to target a specific disease, either for prevention or treatment, has long been recommended. The impact of exercise on insulin regulation and blood sugar control is well documented. According to the CDC, the number of Americans diagnosed with diabetes has more than tripled from 1980 to 2008.[10] Effective prevention and treatment of diabetes will be at the cornerstone of controlling healthcare costs and preventing diabetes-associated comorbidities. Exercise has been shown to increase glycogen synthesis, increase free fatty acid delivery and uptake in the muscle, stabilize key proteins involved in insulin signal transduction, improve mitochondrial function, increase capillary density, and improve blood flow to the muscle, as well as demonstrate reductions in tumor necrosis factor-alpha (TNF-alpha).[11] Studies have shown that a moderate-intensity activity, such as brisk walking, at least three days per week, with no more than two consecutive days off between activities is optimal for blood sugar control.[12] Resistance training is believed to be an important addition for blood sugar control, for a minimum of 2 to 3 nonconsecutive times per week.[12] For years, lifestyle changes (i.e., diet and exercise) have been at the forefront of diabetes care, but most patients do not truly dedicate themselves to making consistent changes, and physicians do not have the time to stress its importance. If the Diabetes Prevention Program has highlighted anything, it is that continued support, education, and accountability for patients are crucial to make lifestyle changes consistent and effective.[13]

Physical Activity Recommendations
For adults aged 18 to 64, the United States Department of HHS guidelines recommend 150 minutes of moderate-intensity cardiovascular activity per week or 75 minutes of vigorous activity per week, plus two or more nonconsecutive days of muscle strengthening activity per week.[3] For adults over 65 years, the recommendations are the same. If older adults suffer from a chronic illness, the recommendations stress that older adults should be as active as their disability allows. The guidelines emphasize that inactivity should be avoided and that the more activity the greater the health benefits. It is important to keep in mind that these recommendations are for health benefits, not for optimizing weight loss or weight maintenance. Regardless of the initial goal of activity, this is a good starting place for most patients, especially if they are currently sedentary. The recommendations advise that patients without a diagnosed chronic condition (e.g., diabetes, coronary artery disease, arthritis) and patients who do not have cardiac symptoms do not need to consult a physician prior to starting moderate-intensity activity.[14]

The recommendations for weight loss and weight maintenance start at the same point of 150 minutes of activity per week, but according to American College of Sports Medicine, patients who are overweight and obese will see greater weight loss and enhanced prevention of weight gain with doses of activity at 250 to 300 minutes per week.[15] It is at this point that the recommendations become blurred for patients and really require individualization.  The National Weight Control Registry has demonstrated consistently that high levels of activity (i.e., over 60 minutes of activity per day) are critical to prolonged weight loss success and many studies have shown that regular physical activity is fundamental to long-term weight loss success and maintenance.[16]

How Much is Enough?
The amount of physical activity necessary really depends on each patient’s goals. Is the ultimate goal weight loss, blood pressure reduction, improved functional status, or weight maintenance? For many patients who are losing weight or maintaining weight loss the amount of activity they need to reach that goal varies and individualizing activity recommendations is key. For some patients, 45 minutes a day is sufficient, while others need more. For those aiming for fitness goals or preserving lean mass during active weight loss, recommendations should specifically target a combination of resistance and cardiovascular activity based on individual patient preferences.

Selling the Importance of Physical Activity
It is important to approach exercise recommendations individually, because activity is not a one-size-fits-all prescription. Studies show as little as 3 to 8 minutes per patient interaction can help to impact patient activity levels.[17] But just talking about it is not enough; physicians need to be committed to seeing their patients change. Physicians should help identify patient barriers and find a way to work around them. When patients complain that they do not have more than 10 minutes to spare, that is ok. Jakicic et al[18] showed that splitting long exercise bouts into small bouts of at least 10 minutes over the day improved patient adherence to regular activity.[18] Four 10-minute bouts can be just as effective, or maybe even more effective, in achieving weight loss and activity goals. If a patient cannot afford a gym membership or personal trainer, that is not a reason to skip out on activity. Studies show that increasing daily lifestyle activities can be just as effective as a structured exercise program in maintaining long-term weight loss.[19] This type of patient might be the ideal candidate for a pedometer, an inexpensive tool to help motivate increasing daily activity. Patients with significant orthopedic limitations, particularly those with superobesity, can benefit greatly from water activities, such as pool walking, water aerobics, and swimming, which can alleviate further weight-bearing stress and decrease the risk of injury. Recommending a variety of exercise options is important to helping patients find activities they enjoy and is key to getting patients coming back for more. Consider ballroom dancing, adult ballet, yoga, pilates, circuit training, or martial arts to add variety to a patient’s exercise routine and help prevent boredom. Variety also helps with cross training and improves strength and fitness because patients work different muscles in multiple ways. Do not forget about exercise or activity videos that patients can use at home like Fit TV or gaming systems, such as Wii Fit. The possibilities go well beyond the gym.

Prescribing and Describing an Exercise Regimen
During brief conversations with patients it can be helpful to carve out how to meet the guideline recommendations of 150 minutes per week. Handing each patient an exercise prescription that includes an activity goal can help to motivate patients as well as keep them accountable. For example, providing a patient with the frequency, duration, and intensity of activity helps him or her avoid wondering what and how much exercise to do. Intensity of exercise can be the most difficult to identify but can be described as low (e.g., light walking), moderate (e.g., moderate walking), and vigorous (e.g., jogging) intensity. Advising patients regarding intensity can be tricky, particularly in regards to METS or percent of predicted max heart rate (PMHR). One MET is defined as oxygen consumption of 3.5mL of oxygen per kilogram per minute, or more simply, the amount of oxygen required when sitting at rest. The greater the intensity of activity results in greater oxygen consumption and the greater the amount of work that can be preformed. The bulk of recommendations should include moderate intensity activity, instructing patients regarding a goal of 4 to 6 METS, 50 to 65 percent of PMHR, or an increase in respiration, but not to the point where patients cannot hold a conversation during activity. Patients should progress slowly from low to moderate to vigorous activity as they can tolerate based on their health, fitness, and medical limitations. Making adjustments to an exercise prescription at each visit helps to keep patients active and reinforce its importance in their health, fitness, and weight-management goals.

Only a handful of studies have looked at the impact of activity in post-bariatric surgery patients and most have all been retrospective studies with limitations related to self reporting.[20] Despite the lack of objective assessment of activity in these patients most studies show an association of exercise and increased weight loss in post-bariatric patients, both band and bypass patients. One prospective assessment of post-bariatric patients assessed activity levels via self reporting as well as quality of life assessments.[21] Bond et al[21] found that patients who were inactive preoperatively and became active postoperatively lost an additional 6kg or eight percent of excess weight. Additionally, these patients had greater improvements in quality-of-life scores related to mental health, general health, and vitality. Results were independent of age, sex, ethnicity, and preoperative weight or body mass index (BMI). Currently, there are no defined activity guidelines for bariatric patients, but limited research suggests that for long-term health, fitness, and weight management benefits, these patients will need to be active.

Conclusion
The importance of regular physical activity and exercise can not be undervalued. As the rates of diabetes and obesity soar to new heights, the steps for prevention and treatment must include lifestyle changes, and specifically increased physical activity. We need to stress this importance with our patients at every visit. The health benefits of activity occur regardless of age and weight loss, and no patient is exempt from the need for activity. The CDC emphasizes the importance of getting Americans moving, with fairly modest recommendations that are designed to not be overwhelming for the majority of patients. These guidelines are a starting place, and patients need to be pushed beyond them on an individual basis regardless of whether they are losing weight after bariatric surgery, maintaining recent weight loss, or optimizing blood glucose levels. With every refill for a medication or prescription for a lab test, we need to include a prescription for exercise. We must remind patients at every visit of the benefits of an active lifestyle because the long-term risks of inactivity are far too great.

References
1.    Centers for Disease Control and Prevention. US Obesity Trends. http://www.cdc.gov/obesity/data/trends.html Accessed January 31, 2011.
2.    Centers for Disease Control and Prevention. Behavioral Risk Factor Surveillance System, 2005. www.CDC.gov/
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23.    Bravata, D, Smith-Spangler C, Sundaram V, et al. Using pedometers to increase physical activity and improve health: a systematic review. JAMA. 2007;298(19):2296–2304.
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