regular physical activity. • Physical activity improves physical function among individuals of all ages, enabling them to conduct their daily lives with energy and without undue fatigue. This is true for older adults, for whom improved physical function not only reduces risk of falls and fall-related injuries but contributes to their ability to maintain independence. It is also true for young and middle-aged adults, as improved physical function is manifested in the ability to more easily accomplish the tasks of daily living, such as climbing stairs or carrying groceries. Some benefits happen immediately. A single bout of moderate-to-vigorous physical activity will reduce blood pressure, improve insulin sensitivity, improve sleep, reduce anxiety symptoms, and improve cognition on the day that it is performed. Most of these improvements become even larger with the Part A. Executive Summary 2018 Physical Activity Guidelines Advisory Committee Scientific Report A-3 regular performance of moderate-to-vigorous physical activity. Other benefits, such as disease risk reduction and physical function, accrue within days to weeks after adopting a new physical activity routine. Physical activity reduces the risk of a large number of diseases and conditions. The past 10 years have greatly expanded the list of diseases and conditions for which greater amounts of physical activity reduce the risk. Some of the major results include: • Strong evidence demonstrates that greater volumes of moderate-to-vigorous physical activity are associated with preventing or minimizing excessive weight gain in adults, maintaining weight within a healthy range, and preventing obesity. This is important because losing weight is difficult and costly. • Strong evidence demonstrates that higher amounts of physical activity are associated with a reduced risk of excessive increases in body weight and adiposity in children ages 3 to 17 years. • Strong evidence also demonstrates that more physically active women are less likely to gain excessive weight during pregnancy. They also are less likely to develop gestational diabetes or develop postpartum depression than their less active peers. Maternal and child health has been, appropriately, a priority in the United States for generations. These findings indicate that physical activity is an important tool in the maintenance of maternal health, and affects a key time period when establishing lifelong healthy behaviors can be beneficial to women and their children alike. • Strong evidence demonstrates that greater volumes of physical activity reduce the risk of dementia and improve other aspects of cognitive function. Given the high and rising prevalence of older Americans and the expense and heartache of caring for individuals with dementia, the value of preventing dementia is high. • For the first time, the 2018 Scientific Report demonstrates that regular physical activity provides health benefits to children as young as ages 3 to 5 years. The 2008 Committee was unable to reach a conclusion about this young age group because of insufficient information. A substantial increase in evidence since then has allowed the 2018 Committee to conclude that, in addition to the reduced risk of excessive gains in body weight and adiposity, regular physical activity improves bone health in this young age group. These findings call attention to the importance of establishing healthy physical activity behaviors at an early age. • For older adults, strong evidence demonstrates a reduced risk of falls and fall-related injuries. Part A. Executive Summary 2018 Physical Activity Guidelines Advisory Committee Scientific Report A-4 • The 2008 Committee concluded that regular moderate-to-vigorous physical activity reduced the risk of breast and colon cancer. The 2018 Committee expanded that list to include a reduced risk for cancers of the bladder, endometrium, esophagus, kidney, lung, and stomach. • A large portion of the general population already has a chronic disease or condition. The 2018 Committee has concluded that, for many of these individuals, regular physical activity can reduce the risk of developing a new chronic condition, reduce the risk of progression of the condition they already have, and improve their quality of life and physical function. The conditions examined by the Committee included some of the most prevalent, including osteoarthritis, hypertension, and type 2 diabetes. The benefits of physical activity can be achieved in a variety of ways. The public health target range suggested in the 2008 Scientific Report was 500 to 1,000 MET-minutes of moderate-to-vigorous physical activity (or 150 to 300 minutes per week of moderate-intensity physical activity). The 2018 Committee concurs with this target range. Unfortunately, half the U.S. adult population does not currently attain this level of physical activity. Thirty percent of the population reports doing no moderate-to-vigorous physical activity. Thus, for a large segment of the population, major improvements in health are available from modest increases in regular physical activity. The 2008 Committee reported that inactive individuals can achieve substantial health gains by increasing their activity level even if they do not reach the target range. Since 2008, substantially more information in the scientific literature documents the value of reducing inactivity even if the 150- to 300- minute weekly