Obesity and overweight

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The prevalence of Overweight and Obesity is high in the general population. The main risk factors are sedentary behaviour and low levels of physical activity. However, exercise improves physical function and reduces adipose tissue in obese individuals.

CONTENTS

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What are obesity and overweight?
What is the prevalence of overweight and obesity?
What are the risk factors for obesity?
Is exercise useful for the treatment of obesity?
Are combined exercise and lifestyle interventions helpful for the treatment of obesity?
Are adolescent prevention programs useful for the treatment of obesity?
Evidence-based recommendations for exercise
Conclusions
References

What are obesity and overweight?

Obesity arises from an individual being in a chronically positive energy balance. This is a state in which energy intake is greater than energy expenditure. However, the condition is recognised to be a multifaceted issue that includes genetic, environmental and cultural influences and the rising standard of living in the developed world. Globally, Obesity and Overweight are now the primary nutritional problem, surpassing malnutrition and infectious disease as the most important contributor to mortality and ill health (Lau et al.). Obesity and Overweight are often defined by reference to Body Mass Index (BMI), where Overweight is defined as a BMI of >25kg/m2 and Obesity is defined as a BMI of >30kg/m2.


What is the prevalence of overweight and obesity?

The following table shows the results of various studies that have investigated the prevalence of Obesity and Overweight in various populations:

Study Population Prevalance
Flegal et al. United States Male Adults >25 BMI 59.4%
Flegal et al. United States Female Adults >25 BMI 50.7%
Mokdad et al. United States Male Adults >30 BMI 17.9%
Mokdad et al. United States Male Adults 18-29 years >30 BMI 12.1%
Mokdad et al. United States Hispanic Adults >30 BMI 20.8%
Flegal et al. United States Age adjusted 30.5%
Flegal et al. United States Adults >40 BMI 4.7%
Ogden et al. United States Adults >30 BMI 32.2%
Ogden et al. United States Male Adults >30 BMI 31.1%
Ogden et al. United States Female Adults >30 BMI 33.2%
Flegal et al. United States Male Adults Age Adjusted >30 BMI 35.5%
Flegal et al. United States Female Adults Age Adjusted >30 BMI 35.8%
Janssen et al. Maltese Youth 10-16 years >30 BMI 7.9%
Janssen et al. United States Youth 10-16 years >30 BMI 6.8%
Rennie et al. United Kingdom Male Adults 23%
Rennie et al. United Kingdom Female Adults 25%
Thorburn et al. Australian Male Adults 19%
Thorburn et al. Australian Females Adults 22%
Jebb et al. England 4-18 years 2.9%
Jebb et al. Scotland 4-18 years 7.6%
Jebb et al. Wales 4-18 years 6.5%

Based on these studies, it appears the prevalence of overweight and obesity range from 2.9% – 50% depending upon the exact definition, the gender, age range and ethnicity of the population.

What are the risk factors for obesity?

There are several risk factors that increase the likelihood of long-term weight gain leading to obesity. The following studies show the extent of the risk factors that increase the likelihood of weight gain leading to obesity:

Study Method Finding
Kelishadi et al. The researchers investigated the national prevalence of overweight and obesity in 89,532 subjects aged over 15 years living in Iran and the association of certain lifestyle behaviours. The researchers found that no significant differences were observed in the frequency of consumption of food groups in different BMI categories. Additionally, they found physical activity declined with increasing BMI.
Hu et al. The researchers examined the relationship between various sedentary behaviours and their associations with obesity in 50,277 women free from obesity and type 2 diabetes mellitus over 6 years of follow up taking part in the Women’s Health Study. The researchers found that the women who were <30 BMI at the start of the study, 7.5% had became obese. They found that television watching and sitting at work were both positively associated with the risk of obesity. They report that each 2 hour increment of TV watching or sitting at work corresponded to a 23% and 5% increase in the risk of developing obesity respectively. In contrast, they report that each 2 hour increment of standing or walking at home, or 1 hour of brisk walking per day was related to a 9% and 24% reduction in the risk of obesity respectively.
Monasta et al. The researchers examined the association between early life characteristics and the onset of adult obesity using a review of systematic reviews process, including 12 eligible studies. The researchers found positive associations between maternal diabetes and smoking, rapid infant growth, no or short breastfeeding, obesity in infancy, short sleep duration, <30 minutes of daily physical activity and consumption of sugar-sweetened beverages and the risk of later overweight and obesity.
Durand et al. The researchers investigated the association between housing and community environmental factors on physical activity and body mass including 204 studies. The researchers found that several factors were associated to physical activity (primarily walking) including housing density, diverse housing type, land space and mixed land use. However, the researchers report that no associations between community environmental factors and body mass were found.
Spiegel et al. The researchers performed a review investigated the association between sleep behaviour and disorders on glucose metabolism and risk of obesity. The researchers reported that short sleep duration as well as sleep disorders such as obstructive sleep apnoea are associated with increased obesity risk.
Wang et al. The researchers investigated the prevalence of obesity and correlates that may predict at risk populations in United States adults. The researchers found that prevalence of obesity was greater among minority and low socio-economic individuals.
He et al. The researchers examined the effect of long term changes in fruit and vegetable intake over 12 year follow and its relation to obesity and weight gain 74,063 female nurses aged 38 – 63 years. The researchers found that over the 12 years the participants tended to gain weight with ageing. They report that in those that ate the largest amount of fruits and vegetables had a 24% reduced risk of becoming obese.
Liu et al. The researchers investigated the association between dietary fibre intake and the development of weight gain leading to obesity in 74 091 US female nurses, aged 38 – 63 years during follow up from 1984 to 1996. The researchers found that those women who ate more fiber and whole grains weighed significantly less than those with significantly less fibre intake. They found that women with the highest intake of fibre were 49% less likely to have major weight gain compared to those with the lowest dietary fiber intake.
Mozaffarian et al. The researchers investigated the association of changes in lifestyle factors and increases in weight gain in 120,877 US women and men free from chronic disease and obesity at baseline. The researchers examined these associations in three cohorts between 1986 to 2006, 1991 to 2003, and 1986 to 2006. The researchers found that long term weight gain was associated with changes in dietary behaviours including intake of potato chips, potatoes, sugar-sweetened beverages and inversely related to intake of vegetables, whole grains, fruits, nuts and yogurt. They also found that weight gain was related to changes in lifestyle factors such as physical activity, alcohol use, smoking, sleep (<6 or >8 hours) and television watching.

Based on these studies, it appears that high amount of sedentary behaviour and other inactive lifestyle behaviours such as television watching, ethnicity and socioeconomic status, and nutritional behaviours are all significant risk factors for developing obesity.

Is exercise useful for the treatment of obesity?

A number of exercise interventions have been performed to assess the effect of general physical activity, supervised or unsupervised structured exercise on obese individuals, as shown in the table below:

Study Method Finding
Bolognesi et al. The researchers examined the effect of a brief GP physical counselling session on subsequent changes in BMI and abdominal girth, as well as readiness for physical activity and self-efficacy. A total of 96 participants, 48 intervention and control participants, took part in the study where they received either a patient-centred assessment and counselling of exercise (PACE) protocol by a General Practitioner, or a usual care protocol respectively. The researchers found that significant reductions in BMI and abdominal girth after 5 – 6 months of the intervention. Further, they report that participants in the intervention group had progressed in their stage of readiness and significantly increased their self-efficacy.
Quinn et al. The researchers performed a pilot trial to investigate the effect of a physical activity group based education intervention to improve changes in physical activity, cardiovascular fitness, quality of life and attitudes towards exercise. The researchers recruited 18 obese Irish females aged 37 years to receive monthly group physical activity education sessions and subsequently measured changes in cardiorespiratory fitness, physical activity, physical activity-related quality of life and attitudes towards exercise. The researchers found the intervention significantly increased cardiovascular fitness an attitudes towards exercise, but observed no changes in body weight or weight-related quality of life scores.
Lee et al. The researchers investigated the effect of exercise without weight loss as a potential strategy for obesity reduction in obese and lean men with and without type 2 diabetes. The participants undertook 13 weeks of supervised aerobic training at 60% peak oxygen uptake 5 days per week, while measures of total and regional body composition were taken at baseline and post intervention. The researchers found no changes in weight following the 13 week intervention programme. However, the researchers found significant improvements in total, subcutaneous and visceral fat in both groups with no difference between them. Improvements in total muscle and high density muscle area accounted for the reduction in fat mass in both groups and therefore improved the skeletal muscle to body fat ratio in both groups.
Lee et al. The researchers investigated the effect of different exercise modality on abdominal fat, intrahepatic lipid and insulin levels in obese adolescent boys. Forty-five boys were randomly allocated to either an aerobic, resistance or no exercise control group receiving a 3 month intervention. The researchers determined abdominal fat, intrahepatic and insulin levels pre and post intervention. The researchers found that both exercise interventions prevented weight gain during the 3 month period but the control group experienced a significant increase in body mass. Following the 3 months, both exercise groups showed significant reductions in total and abdominal fat and intrahepatic lipids. Further, compared to the control group, the resistance training group experienced a 27% improvement in insulin sensitivity.
Johnson et al. The researchers investigated the effect of aerobic exercise training on the reduction of hepatic lipids and non-alcoholic fatty liver disease. Nineteen sedentary obese men and women took part in 4 weeks of aerobic cycling exercise in accordance with recommended guidelines for physical activity and measures of hepatic, blood, abdominal and muscle lipids were taken pre and post intervention. The researchers found that following the intervention visceral adipose tissue and hepatic triglyceride concentrations reduced by 12% and 21% respectively. The researchers conclude that in the absence of body weight reduction, improvements in hepatic triglycerides follow aerobic exercise training.
Rice et al. The researchers investigated the effect of diet in combination with either aerobic or resistance training on glucose and insulin levels and whether these are different in obese men, and secondly, whether diet and exercise is superior than diet alone in obese men. The researchers found that reduction in weight, visceral and subcutaneous adipose tissue was similar between both exercise groups. Further, both exercise groups preserved skeletal muscle mass whereas lean mass was reduced in the diet only group. Fasting glucose and insulin did not change in any group, but changes in fasting and post glucose load insulin was reduced with greater reductions following both exercise interventions than diet alone.
Sarsan et al. The researchers investigated the effect of aerobic and resistance training in 60 obese women randomly allocated to either aerobic, resistance or no-exercise control for 12 weeks on weight, muscle strength, cardiovascular fitness, blood pressure and mood. The researchers found that resistance-training significantly improved maximal dynamic strength whereas aerobic training significantly improved peak oxygen consumption and scores of the beck depression scale compared with controls.
Schmitz et al. The researchers investigated the effects of 15 weeks of supervised twice-weekly strength training on the changes in fat free mass, total and percent fat body mass following 6 months of unsupervised training in 60 women aged 30 – 50 years between 20 – 35 BMI. The researchers found that improvements gained during the supervised training period were largely maintained and session adherence was over 90% after 6 months. They found that compared to the control group, the strength training group had significantly more fat free mass (0.89kg), less fat body mass (0.98kg) and less percent body fat (by 1.63%). The researchers note that weight loss or waist circumference was not significantly different following the intervention.
Jakicic et al. The researchers performed a review investigating the considerations for daily physical activity for preventing weight regain or preventing weight gain in obese individuals. The researchers suggest that although 30 minutes per day is adequate for improvements in health outcomes, obese individuals may require upwards of 60 minutes a day to induce significant weight loss or prevent weight regain.
Perri et al. The researchers investigated the effect of two aerobic exercise interventions on exercise participation, health behaviours and weight changes in 49 obese women following a 1 year behavioural weight loss program. The participants were randomly allocated to a diet plus either group or home based exercise program consisting of three supervised group exercise sessions per week for 26 weeks then twice weekly thereafter or instructions to walk for 30 minutes, 5 days per week. The researchers report that following the intervention, the home-based program showed significantly greater participation and adherence compared to the group training, and significantly greater weight loss following 15 months.
Park et al. The researchers aimed to investigate the effect of combined aerobic and resistance training on changes in abdominal adipose tissue in 30 obese women. The women were randomly allocated to an aerobic training, combined training or control group and received either 60 minutes of aerobic training at 60 – 70% HRmax, 6 days per week or resistance-training and aerobic training 3 times per week each. The researchers observed a significant reduction of subcutaneous and visceral fat in both groups but the results were superior in the combined group. Further, lean body mass was increased in the combination group only. They found that total cholesterol, LDL-C and triglycerides were significantly reduced and HDL-C increased in both groups.
Fenkci et al. The researchers investigated the effect of aerobic or resistance training on changes in metabolic parameters and body composition in obese women who were unable to adhere to a restricted diet. The patients were 60 obese women who were randomly allocated to an aerobic training, resistance training or control group and subsequently undertook a 12 week exercise program. The researchers found that 12 weeks of either exercise program significantly improved BMI, waist and weight measurements, fasting and postprandial glucose and insulin levels, triglycerides and total cholesterol. Further, they report that combined training improved fat mass and insulin sensitivity compared to aerobic alone.
Ohkawara et al. The researchers performed a systematic review to investigate the relationship between exercise volume and visceral fat reduction including 9 randomised control trials and 582 participants. The researchers suggest that 10 MET/hours per week is required for reduction in visceral fat and a dose response relationship exists between volume of aerobic exercise and change in visceral fat in obese adults without metabolic disorders.

Based on these studies, it appears that physical activity and exercise interventions are beneficial for obese individuals for improving cardiovascular risk, reducing intrahepatic lipids, subcutaneous and visceral fat. Further, greater levels of physical activity may benefit weight loss and minimise weight regain.


Are combined exercise and lifestyle interventions helpful for the treatment of obesity?

A number of combined exercise and lifestyle interventions have been performed to assess the effect of general physical activity, supervised or unsupervised structured exercise in combination with other lifestyle interventions on obese individuals, as shown in the table below:

Study Method Finding
Maffiuletti et al. The researchers investigated the short and medium term (1 year follow up) outcome of a hospital based weight reduction program in severely obese individuals participating in 3 weeks of an energy restricted  diet, tailored aerobic-strength exercise and behavioural counselling. The participants were measured for changes in body composition, physical performance and cardiovascular risk factors before, immediately after the intervention and after 49 weeks of indirect supervision at home. The participants were 45 and 19 women and men respectively, aged 30 years with BMI of 41kg/m2. The researchers report that there were more meaningful successes among the women (82%) compared to the males (60%) with respect to weight losers. They found that weight losers had significantly greater percent fat free mass, greater strength, greater HDL-C and lower glucose levels, greater self reported physical activity.
Donnelly et al. The researchers investigated the effect of exercise modality in combination with 90 days of a low-calorie diet (2,184kJ per day) on changes in body weight, body composition and resting metabolic rate in obese females. The researchers randomly allocated the subjects to either diet only, diet plus endurance exercise, diet plus weight training, or diet plus endurance exercise and weight training. The researchers found no significant differences in any measures comparing the exercise interventions to diet alone.
Andersen et al. The researchers examined short and long term changes in weight, body composition and cardiovascular risk profiles in obese participants receiving 16 weeks of a diet plus structured exercise intervention, or diet plus moderate intensity lifestyle activity intervention. The subjects were 40 obese women aged 43 years. The researchers found a non-significant trend for greater weight loss and significantly greater preservation of muscle in the structured exercise intervention compared with the lifestyle activity. However, at 1 year of follow up, the structured exercise group had regained 1.6kg of body weight while the lifestyle activity group had regained just 0.08 kg. The researchers reported that a diet plus lifestyle intervention may offer similar yet longer improvements in health benefits for obese women.
Wadden et al. The researchers performed a randomised control trial investigating the effect of 4 different combination diet and exercise interventions lasting 48 weeks on body composition, resting energy expenditure, appetite and mood in 128 obese women. The participants were allocated to: diet alone, diet plus aerobic training, diet plus strength training, or diet combined with aerobic and strength training and received 3 supervised sessions per week for 28 weeks and 2 sessions weekly thereafter. The researchers found that participants achieved a mean weight loss of 16.5 kg after 24 weeks, which decreased to 15.1kg after 48 weeks with no significant difference between groups. They report that no significant differences were observed in any variables between groups.
Weinstock et al. The researchers investigated the effects of a combination diet and exercise program lasting 48 weeks. The participants were randomly allocated to 48 weeks of a supervised of diet alone, diet and aerobic or diet and resistance training and measured for insulin resistance and body composition at baseline, 16, 24, 44 weeks and after an unsupervised weight regain period (week 96). The researchers found that weight loss averaged 13.8 kg by week 16 for the three groups, which correlated with a significant reduction of insulin levels (61.8% of baseline). Further, the researchers found no significant changes in BMI, weight, glucose or insulin tolerance at week 16, 24 or 44. The researchers conclude that exercise training did not result in additional weight loss or insulin sensitivity but weight loss has positive benefits on hyperinsulinemia.
Geliebter et al. The researchers investigated the effect of progressive resistance training or aerobic cycling and arm crank exercise on body composition, metabolic rate in 65 obese subjects receiving an 8 week intervention of a diet representing 70% resting metabolic rate and one of two exercise intervention. The researchers found that resistance training significantly preserved skeletal muscle mass compared to diet and aerobic training and diet alone, but did not alter the decline in metabolic rate observed in all groups. Mean weight loss was 9 kg and did not differ between groups.
Sweeney et al. The researchers investigated the effect of a severe (40%) or moderate (70%) restricted diet and aerobic or aerobic plus circuit weight training on 30 obese women on body composition and efficiency of weight loss. The researchers found that exercise training had no effect on the magnitude of weight loss, but greater weight loss was observed in the severe restricted diet group. However, the diet efficiency was greatest in the moderate energy restricted diet, which the researchers conclude may be advantageous.
Villareal et al. The researchers investigated the effect of diet plus exercise in older adults aged >65 years and obese in measures of physical performance, body composition, and measures of physical ageing. The participants were 93 obese adults >65 years who were randomly allocated to a 1 year weight management diet, an exercise program, or a combination group. The researchers found that follow up measures of physical performance were significantly greater in all groups but superior following the combination group.  Body weight reduced by 10% and 9% in the combination and diet groups respectively, where no change in weight was observed in the exercise alone or control group. Lean body mass and bone mineral density decreased less in the combination group compared to the diet only group. Further, strength, gait and balance improved significantly in the combination group. The researchers conclude that a combination of weight loss and exercise has superior improvements in physical function than exercise or diet alone.
Goodpaster et al. The researchers investigated the effect of a combination diet and physical activity program on changes in health risks that accompany severe obesity. The participants were 101 severely obese adults signed up for an intensive lifestyle intervention. The participants either received a lifestyle intervention consisting of diet and exercise for 12 months or the same intervention but with physical activity delayed for 6 months. The researchers found that after the initial 6 months the group receiving physical activity had lost significantly more body weight (10.9 kg vs. 8.2 kg) compared to the delayed physical activity group. However, after 12 months, there were no significant differences between the groups (12.1 kg vs. 9.9 kg). Waist circumference, visceral abdominal fat, hepatic fat content, blood pressure and insulin levels were all significantly improved in both groups, however, superior improvements in hepatic fat content and waist circumference were observed following the diet and physical activity group. They conclude that an intense lifestyle intervention with initial or delayed physical activity is an effective therapy for significant weight loss and favourable changes in cardio-metabolic risk factors.
Frimel et al. The researchers investigated the effect of adding exercise to a hypo-caloric diet to frail obese older adults aged 70 years in 30 participants. Obese older adults were randomly allocated to a diet and behavioural therapy intervention with and without progressive resistance training on changes in appendicular skeletal muscle mass and strength. The researchers found that both groups lost equal body weight but the exercise group lost less total, lower and upper skeletal muscle mass. The resistance training group improved strength whereas the group not exercising maintained strength. They conclude that resistance training added to a hypo-caloric diet can attenuate the loss in skeletal muscle and increase strength in obese frail older adults.
Wycherly et al. The researchers investigated the effect of two different diets differing in the protein to carbohydrate ratio with and without resistance training exercise on weight loss, body composition and cardiovascular disease risk factors in 59 obese type 2 diabetics. The participants were randomly allocated to receive 16 weeks of thrice weekly supervised progressive resistance training or control in combination with the diet interventions. The researchers found that significantly greater reductions in body weight, fat mass and waist circumference were found following the high protein resistance training group. They found that fat-free mass, blood pressure, glucose, insulin, A1C, triglycerides, total cholesterol and LDL cholesterol were al significantly reduced, with no difference between groups.

Based on these studies, it appears the addition of exercise to dietary and behavioural interventions that produce significant weight loss often improves body composition, physical function, bone mineral density, intrahepatic and visceral fat content.


Are adolescent prevention programs useful for the treatment of obesity?

A number of studies have assessed the effect of targeting sedentary and/or physical activity behaviours in adolescent individuals, as shown in the table below

Study Method Finding
Epstein et al. The researchers investigated the effect of either a prevention program targeting reducing sedentary behaviours compared with increasing physical activity in children aged 8-12 years on subsequent weight control. The intervention was a comprehensive family-based behavioral weight control program that included behaviour information of dietary changes and either changes in sedentary or physical activity behaviour. The researchers found that after 2 years targeting either physical activity or reducing sedentary behaviour was associated with better weight control, reduced body fat and increased aerobic fitness. The researchers report that self reported activity minutes increased and sedentary activities were substituted with targeted non-sedentary activities.
Sacher et al. The researchers investigated the effect of the Mind, Exercise, Nutrition, Do it (MIND) program, a multi component obesity program of 116 obese children in the UK (BMI >98th percentile). The children were randomly assigned to an intervention or waiting list control group where the intervention group included 18 two-hour educational and physical activity sessions followed by 12-week free family swim pass. The researchers measured waist circumference, BMI, body composition, physical activity level, sedentary activities, cardiovascular fitness, and self-esteem at baseline and at 6 months. The researchers found that the intervention group significantly reduced their BMI z-score (-0.24) and waist circumference z-score (-0.37) at 6 months compared to the waiting list control group. Further, the intervention group increased their cardiovascular fitness, physical activity, non-sedentary activity minutes and self esteem. Further, greater changes in z-score waist circumference (-0.47), cardiovascular fitness, physical activity, non-sedentary activity minutes and self-esteem were observed.
Resnicow et al. The researchers investigated the effect on the Go Girls, church-based exercise and behavioural change intervention program including 123 girls from 10 churches. Girls were either allocated to a high intensity (20 – 26 sessions) or moderate intensity (6 sessions) culturally-tailored, behavioural delivered over 6 months. Measurements of BMI, as well as waist and hip circumferences, percentage body, serum insulin, glucose, and lipids, and cardiovascular fitness were assessed at baseline and 6 months. The researchers found that no significant changes were observed following either intervention where changes in BMI were 0.5 BMI units. However, in girls that participated in at least ¾ of the high intensity sessions, significant reductions in BMI compared to girls attending fewer sessions in the same group were observed.

Based on these studies, it appears that interventions targeting reductions in sedentary behaviour or increasing physical activity may have positive benefits in obese and non-obese adolescents.

[Tweet “↓ sedentary behaviour + ↑ physical activity may help obese adolescents @Exercise4NCDs”]


Evidence-based recommendations for exercise

A number of guidelines have been prepared relating to the management and/or prevention of obesity. These have provided evidence-based recommendations for the use of exercise and physical activity to treat obesity and overweight, as shown below:

Guidelines Comments
Canadian clinical practice guidelines on the management and prevention of obesity in adults and children Individuals considering vigorous exercise should consult with an allied health professional or physicians. A long term physical activity plan that maintains or produces a modest reduction in body weight is suggested. Physical activity should be sustained and tailored to the individual, progressing gradually in duration to maximize the weight loss benefits. A physical activity that is moderate intensity for 30 – 60 minutes per day is suggested be part of a weight loss program. Endurance training may be useful to reduce the risk of cardiovascular morbidity in postmenopausal women.
Canadian clinical practice guidelines on the management and prevention of obesity in adults and children Allied health professionals and physicians are suggested to encourage children to reduce ‘screen time’ and other sedentary behaviours. Activity is suggested to be prescribed that is fun and recreational, with lifestyle activities that suit the relative strengths of the child and family. The short term benefits of physical activity are encouraged to be highlighted rather than long term health benefits.
Clinical practice guidelines for the management of overweight and obesity in adults. In: Council NHMR The guidelines include a consensus-based recommendation for physical activity and exercise intervention as a component for weight management. The researchers suggest that obese and overweight individuals should be prescribed 300 minutes of moderate intensity exercise or 150 minutes of vigorous intensity, or an equivalent combination of moderate intensity and vigorous activities each week combined with reduced dietary intake. Further, the researchers report that brief advice delivered through primary health care in person, phone or mail for sedentary individuals has been shown to be cost effective. Similarly, exercise referral schemes and assessment and prescriptions may also provide a cost-effective option.
Management of obesity in adults: European clinical practice guidelines The European clinical practice guidelines suggest physical activity as part of the primary management strategy for obesity. The guidelines suggest that physical activity be an integral part due to the pleotropic effects of physical activity such as: increasing energy expenditure, promoting fat loss, attenuating the weight loss-related decline in metabolic rate, improving physical fitness, improving dietary adherence and long term weight maintenance, and causing positive improvements in self-esteem and wellbeing, and reduces depression and anxiety. The guidelines suggest that efforts to increase physical activity (walking, cycling or using stairs etc.) as well as reducing sedentary times (television watching and computer use) be employed. They report that individuals should be advised and helped to undertake tailored physical activity or exercise that is safe and appropriate, with gradual progress. The guidelines suggest that individuals undertake 30 – 60 minutes of moderate intensity physical activity (perhaps brisk walking) most, if not all days of the week.
Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults – The Evidence Report. National Institutes of Health The guidelines report that physical activity is an important component of weight loss therapy and is important in contributing to energy expenditure and reducing CVD risk factors beyond that produced through weight loss alone. The guidelines note that: physical activity is a contributing component of weight loss, both alone and when combined with dietary interventions, that physical activity in overweight and obese individuals improves cardiorespiratory fitness independent of weight loss, which may lead to improved quality of life, that physical activity alone reduces the cardiovascular risk factors and reduces the risk for cardiovascular disease, and that physical activity contributes to reducing body fat, including a modest effect on abdominal fat.
Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults – The Evidence Report. National Institutes of Health These guidelines recommend certain considerations when implementing strategies for physical activity, as follows: initially, an individual is likely to posses little training and skills in physical activity and thus supervision may be important for adherence, initially, extremely obese or individuals with musculoskeletal risk factors may require simple exercises that are gradually increased in intensity, based on a persons age, symptoms and concomitant risk factors, it is the practitioners decision whether the individual requires exercise testing for cardiopulmonary or other related comorbidities, before embarking on an exercise intervention, and initially, moderate levels of physical activity for 30 – 45 minutes, 3 – 5 days per week should be encouraged, with a long term goal progressing to >30 minutes on most, if not all days of the week.
Obesity guidance on the prevention, identification, assessment and management of overweight and obesity in adults and children (NICE) The guidelines report recommendations for the public in the area of physical activity. They report that enjoyable activities like walking, cycling, swimming and gardening should be made a part of every day life, that the duration of television watching and other sedentary activities should be minimized, that activity should be built into normal working hours, e.g. taking the stairs and walking at lunch breaks etc.
Guideline for the Management of Overweight and Obesity in Adults (AHA/ACC/TOS) The guidelines review the efficacy of physical activity in combination with a comprehensive lifestyle intervention. The guidelines suggest that the components of an effective lifestyle intervention are a reduced calorie diet, increased physical activity and behavioral therapy. The guidelines recommend increased aerobic activity for >150 minutes per week (equal to 30 minutes per day, most days of the week. The guidelines recommend higher levels of activity, approximately 200 – 300 minutes per week to maintain lost weight or avoid weight regain long-term (>1 year).

Based on these guidelines, it appears that individuals are suggested to participate in physical activity in line with the national recommendations to prevent obesity, whereas greater levels of physical activity may be beneficial for weight loss, weight regain, reducing skeletal muscle loss and improving physical function in individuals managing obesity. It also appears that minimising sedentary behaviours is a key guideline for obesity management and prevention.


Conclusions

Based on the above studies and analysis, the following conclusions can be drawn about obesity:

Area Conclusions
Obesity prevalence is high The prevalence of obesity ranges from 2.9% – 50% depending upon the gender, age range and ethnicity of the population.
Sedentary behaviour and low levels of physical activity are key risk factors High levels of sedentary behaviour such as television watching, and low levels of physical activity such as below the recommended guidelines are both significant risk factors for obesity.
Ethnicity and low socioeconomic status are important risk factors Minority ethnicities and individuals with low socioeconomic status are more likely to develop obesity compared to white and greater socioeconomic status in western countries.
Exercise improves physical function in obese individuals General physical activity, aerobic and resistance exercise improves physical function such as dynamic strength, peak aerobic capacity and gait in obese adults.
Exercise reduces adipose tissue General exercise including aerobic and resistance training reduces intrahepatic lipids, subcutaneous and visceral fat. Further, greater levels of physical activity may benefit weight loss and minimise weight regain.
Exercise in combination with lifestyle intervention The addition of exercise to dietary and behavioural interventions that produce significant weight loss often improves body composition, physical function, bone mineral density, intrahepatic and visceral fat content.
Physical activity is effective for weight control in adolescents Interventions targeting reductions in sedentary behaviour or increasing physical activity may have positive benefits of long term weight control, body composition and increasing physical activity levels in obese and non-obese adolescents.
Physical activity and non-sedentary behaviours are effective at preventing obesity General exercise in line with the current guidelines of 30 minutes of moderate exercise most, if not all days of the week is a key recommendation, in conjunction with increasing non-sedentary behaviours such as walking as transport and minimising television watching are effective for weight control and preventing obesity.

In summary, the prevalence of Overweight and Obesity is high and the main risk factors are sedentary behaviour and low levels of physical activity. However, exercise improves physical function and reduces adipose tissue in obese individuals.


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