How is Physical Activity affect obesity?
1-Physical Activity and Prevention of Obesity
physical activity, Overweight describes a multifactorial disease with complicated pathophysiological communications between hereditary, endocrine, and cultural and environmental determinants (improper dietary habits and sedentary lifestyle). There is strong scientific proof of the shielding role of an active lifestyle in the inhibition of weight gain and obesity, while a quiet lifestyle is a promoting factor. Over the last decades, industrialization has made a radical reduction in physically active works and professions and a decreased energy consumption for transport (cars, lifts), while free time spent in nonphysically active modes (TV, computers) has considerably increased. Therefore, the modern lifestyle in developed countries, characterized by low daily energy expenditure and great availability of food, regularly causes a positive dynamic balance with a rising predominance of obesity, which has become a disease problem of public health.
About the restriction of weight increase, it must be emphasized that the primary restriction of obesity starts with the maintenance and not with the loss of weight. The risk of weight gain varies over time, and similarly, it does the need to perform physical activity to prevent it. This is supported by cross-sectional evidence of an inverse relationship between weight status (weight or BMI) and that underlines a dose-response relation between weight loss and increased levels of physical activity. The studies support the need to perform at least 150 min of physical exercise per week to control body weight for a long time. In their randomized controlled 12-month trial aiming to reach 300 min per week of moderate-intensity physical exercise.
2- Physical Activity and Weight Loss
Many studies have shown the beneficial effects of reducing weight and body fat in overweight and obese people. The use of physical activity in the therapeutic management of overweight people is essential. Weight loss is tightly linked to a negative energy balance, being a more negative energy balance associated with a greater weight loss. Since an energy deficit of 500–1000 kcal/die is necessary to reduce the bodyweight of 0.5–1 kg per week, achieving this deficit only with the practice is extremely difficult. Physical activity levels reached during military training or in some sports like mountain climbing at high altitude can lead to a meaningful weightloss; getting and keeping these high levels of activity is not feasible for most people. Only a few of the studies evaluating physical activity as the only mean for accomplishing weight loss have manifested a significant weight loss in overweight-obese and inactive people, i.e., greater than or equal to 3 % of baseline weight. Therefore, in the majority of obese individuals, further interruptions (energy limitation or low-calorie diet) over physical activity are needed to obtain a meaningful weight loss.
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How to keep your weight
Whereas the consequences of physical activity only on weight loss are minimum, physical activity has a significant role in the control of the keeping of body weight after weight loss. Physical activity is entirely recommended to maintain body weight after having achieved a meaningful weight loss, and the levels of physical activity are often regarded as the best predictor of the keeping of body weight after a meaningful weight loss. studies showed that an expenditure of 11–12 kcal/kg/die (46.1–50.3 kj/kg/die) is necessary for effective maintenance, whereas data from the National Weight Control Registry, including more than 3000 individuals who got a strong weight loss of at least
13.5 kg for a minimum of 1 year, shows that a greater level of daily physical activity may be crucial to stop weight recovery. These individuals described having used various ways to accomplish weight loss, and more than 90 % of them indicated the practice of high levels of physical activity as important for the long- term keeping of weight.
After initial weight loss by a very low-calorie diet (mean loss 13.1 kg), adding specific activity formulae to the behavioral weight maintenance intervention resulted in a range of weight change at 9 months of −2.7 to +0.3 kg net of the control intervention. After 33 months, participants regained weight, on average between 5.9 and 9.7 kg. The range of weight change for the exercise interruptions was 3.5 to 0.2 kg less than the control weight keeping intervention (differences not statistically significant). There were no significant differences between the two levels of recommended physical exercise—2–3 h per week of walking versus 4–6 h per week—in weight loss maintenance at 1-year post-randomization. In a study from the same group, after a very-low-energy diet for 2 months (mean weight loss
14.2 kg) middle-aged obese men were randomized into a walking, defense training, or control group for 6 months while receiving similar dietary advice. At the
23-month follow-up after the weight maintenance intervention, the mean weight decrease was 4.8 kg with no statistically significant difference between the groups.
In a systematic review on this topic, most of the analyzed studies were observational, while in intervention studies randomization to different levels of physical activity was generally performed before weight loss and follow-up ranged from months to many years. The study of physical activity and the recovery of weight were inversely related, and the higher the level of activity studied the lower was the weight increase. The three studies in which randomization to physical activity occurred after having an initial weight loss showed that it’s had a neutral, negative, or positive effect, respectively, on the inhibition of weight regain.