Continuing Education Activity

Obesity represents a significant and increasing worldwide health problem associated with increased morbidity and mortality, primarily due to an increased risk of cardiovascular disease. Physical activity (PA) and exercise training are commonly used strategies to promote and maintain weight loss in patients with obesity or who are overweight. This is often in combination with calorie restriction, medication, or bariatric surgical intervention. This article reviews the evidence and clinical approach to physical activity for the maintenance of weight loss.

Objectives:

• Describe the physiology of weight loss and weight loss maintenance in patients with obesity or who are overweight.
• Outline the clinical evidence for physical activity in weight loss and weight loss maintenance in patients with obesity or who are overweight.
• Summarize key patient counseling points when advising physical activity to maintain weight loss patients with obesity or who are overweight.
• Explain the importance of accurate counseling by the interprofessional team for maintaining weight loss in patients with obesity or who are overweight.

Introduction

Obesity is a significant and increasing health problem worldwide.[1] It is defined as a body mass index (BMI) of >30kg/m2 or >25kg/m2 with obesity-related comorbidity.[2] Obesity is associated with increased morbidity and mortality, primarily through increased risk of cardiovascular disease, hypertension, and diabetes mellitus (DM).[3][4][5] Reduced levels of physical activity (PA) are associated with obesity. Furthermore, it is independently associated with an increased risk of cardiovascular disease.[6] In general, obesity occurs in response to variable environmental, psychological, and physical factors in genetically susceptible patients.[2]

In simplest terms, weight change depends on the balance between energy intake and energy expenditure. However, this relationship is non-linear and involves many variables such as body mass composition, energy partition, and energy storage.[7] In addition, variables such as baseline metabolism, cardiovascular fitness, lean muscle mass, and body mass all modify energy expenditure associated with PA.[7] The physiologic response to weight loss strategies is an attempt to maintain body weight. Thus, attempts to lose weight through calorie restriction or increased PA trigger responses such as increased appetite and metabolic adaption to minimize net energy loss.[2]

Weight change in patients with obesity is a complex multifactorial problem. Weight loss itself decreases the energy required and thus expenditure to perform equivalent PA activities after weight loss. Negative feedback circuits have been shown to influence food intake by increasing appetite and decreasing satiety.[8] In addition to physiological variables, behavioral and psychological influences are extremely important to consider when treating patients.[9]

Weight loss is the primary treatment for patients with obesity. While some improvement in cardiovascular risk has been demonstrated with a weight loss of 2 to 3%, clinical guidelines recommend a weight loss of 5% to 10% over 6 months to produce significant improvements in cardiovascular risk factors.[10] However, maintenance of weight loss has traditionally been extremely difficult for patients with obesity. In 1959, Stunkard and McLaren-Hume showed that only 2% of 100 patients with obesity maintained significant weight loss at 2 years.[11] More recently, in 2005, Wing and Phelan showed that 80% of 4000 patients in the National Weight Control Registry failed to maintain weight loss after 1 year.[12] Although sustained weight loss is the target, many factors, including cardiovascular fitness and body mass composition, require consideration when treating patients with obesity.

Function

In 2001, the American College of Sports Medicine recommended at least 150 minutes of PA per week to promote and maintain weight loss. However, they advised that 200 to 300 minutes of PA per week would be more effective in maintaining weight loss. This would correlate to 60 minutes of walking per day.[13] However, in 2009, this position was revised to recommend 150 minutes as a minimum level of PA per week, with >250 minutes per week of PA optimal for weight loss maintenance.[14]

Multiple large trials have shown that the volume of PA is directly associated with successful maintenance of weight loss.[15][16][17] However, most studies combined PA programs with calorie restriction. Wing et al. (2004) examined 1079 patients in the Diabetes Prevention Program (DPP) at 1 and 3-year intervals following diet and lifestyle modification. Mean PA levels were 224 and 247 minutes, and weight loss goals were reached in 49% and 37% of patients at 1 and 3 years respectively.[18][19][20] Predictors of successful weight loss after 1 and 3 years were meeting PA targets and self-monitoring of diet.[17] Wadden et al. (2011) used data from The Action for heath for Diabetes (Look AHEAD) study containing 5145 patients with DM to show a direct correlation between the amount of PA and weight loss over 4 years. Patients in the highest quartile of PA completed a mean 287 minutes of exercise per week and showed significant weight loss and maintenance of weight loss after 3 years.  However, successful maintenance of weight loss was shown in only 25% of the starting cohort after 3 years. Predictors of unsuccessful weight loss included poor adherence to PA and diet programs.[18] Jeffry et al. (2003) showed that high-intensity PA (approximately 75 minutes per day) improved maintenance of weight loss compared to lower intensity PA (~35 minutes per day).[19] However, it is essential to note that adherence to the high-intensity exercise program was <50% at 6 months and <40% at 12 and 18 months. This was despite measures taken to improve adherence, including exercise coaching, exercise partners, and behavioral support.[19]

Key protective factors for weight loss maintenance include adherence to high levels of PA, low calorie and low-fat diets, and self-monitoring of weight, diet, and exercise. Conversely, poor adherence to PA and dietary programs was associated with failure to maintain weight loss. The effectiveness of PA in the maintenance of weight loss is limited by patient adherence, thus becoming a complex issue comprising physical, physiological, and behavioral aspects.

There are several limitations of research into weight loss maintenance. The large studies rely on self-reporting of PA levels rather than direct monitoring. Prescribed PA had poor adherence in most studies, and self-reported adherence remains a key predictor of successful maintenance of weight loss.[17][18][19]

PA, independent of calorie restriction, is an effective method for weight loss and weight loss maintenance.[15][16][21]  However, the volume and intensity of PA required to promote and maintain weight loss without calorie restriction are high and difficult for many patients. In addition, variation in patient body shape, mass, and cardiovascular fitness all affect the volume and intensity of PA required to promote and maintain weight loss. Therefore, PA alone is less effective than calorie restriction in weight loss maintenance.[21]

Patients seeking to lose weight without changing dietary habits should be counseled that 225 to 400 minutes of exercise per week could be required, and even then, there is no guarantee of weight loss. This is especially true in patients with a high-calorie intake.[22] To attain weight loss maintenance, patients would likely need to sustain >250 minutes per week of PA. This has been shown to improve weight loss maintenance compared to PA levels of <150 minutes per week.[21] However, in cases of lower PA levels, patients would likely still see health benefits of PA. 150 minutes per week of exercise has been shown to improve cardiovascular health and reduce all-cause mortality in patients with obesity or who are overweight.[22] Therefore, patients should be counseled differently depending on their goal of weight loss, weight maintenance, or improved cardiovascular fitness.

There is less evidence for weight loss in PA alone, rather than in conjunction with calorie restriction. High PA levels alone were shown to improve weight loss in the 1 and 2 Midwest Exercise Trial (MET 1) and (MET 2). MET 1 (131 patients) demonstrated significant weight loss associated with increased PA levels in male but not female patients.[15] MET 2 demonstrated clinically significant weight loss associated with increased PA in all 141 patients randomized to aerobic PA programs.[16] Both MET 1 and 2 used supervised PA, with less than 90% adherence being disqualified from the trial. Other studies have shown that PA programs alone produced no significant weight loss or maintenance of weight loss. However, these used significantly lower levels of PA and utilized unsupervised PA.[23][24]

Predictors of successful weight loss and weight loss maintenance include adherence to PA programs, diet control, and self-monitoring of weight, diet, and exercise programs. Whilst maintenance of weight loss is difficult, successful maintenance at 1 year is a good predictor of consistent maintenance into the future.[12][18][21]

Independent of weight loss, PA effectively improves cardiovascular fitness and reduces cardiovascular risk factors, thereby reducing the morbidity and mortality of obesity.[21][22] Patients who have been unsuccessful with weight loss should be encouraged to maintain PA levels, as this will improve cardiovascular fitness and reduce all-cause mortality independently of weight loss.[22][25] Reinforcing the unseen benefits of increased cardiovascular fitness and reduction in all-cause mortality that is associated with PA is important in patients who are less successful with maintaining weight loss. Ongoing PA is still highly beneficial even if the weight has been regained. In this way, clinicians should aim to shift goals away from just weight loss to include other important aspects of health such as cardiovascular fitness, lean muscle mass, and mental wellbeing.[14][21]

Issues of Concern

Maintenance of weight loss in patients with obesity or who are overweight is difficult due to the physical and psychological effort required to maintain a sustained calorie deficit over long periods. While increasing PA levels have been shown to improve weight loss and weight maintenance, it is associated with worse patient adherence, restricting the effectiveness of programs. The recommended 200-300 minutes of exercise a week remains a large commitment for patients.[15][16][21] In addition, as patients lose weight and cardiovascular fitness improves, the energy expenditure for similar PA declines. As a result, continuing weight loss requires calorie restriction and PA to be modified with changing body habitus. Weight loss and maintenance of weight loss take significant physical effort and time.[19][21]

Poor adherence is common after long periods of intensive diet and PA programs with an apparent lack of results. Unrealistic goal setting, including prescription of unsustainable PA or calorie restriction levels, often leads to poor patient adherence, lack of results, and subsequent disillusionment and mistrust.[19][21] Therefore, management of expectations is an essential part of encouraging patients to continue to adhere to programs that will take more time and effort than the patient is expecting.[9][26] It is important to continue to reinforce a realistic and consistent message to patients concerning their weight loss.

Patients with obesity or who are overweight, especially those with other co-morbidities, may find PA difficult. Walking is often recommended as an accessible form of PA. However, patients with an ongoing musculoskeletal disorder or other disabling comorbidities may not be able to walk for the necessary time to promote significant energy expenditure.[14] Other options include non-weight-bearing aerobic or resistance training such as swimming or sitting exercises. As predictors of weight loss maintenance are patient self-monitoring and adherence, patient choice and ability should be considered during PA counseling for patients with obesity or who are overweight.[14][21]

The psychological component of maintaining a significant weight loss is crucial. Mood and eating disorders can greatly impact patients’ weight and can be a limiting factor in successful weight loss. Management of eating disorders or body dysmorphia by appropriate specialists is essential to promote weight loss and weight loss maintenance. In addition, effective management of concordant mental health issues by appropriate specialist consultation can promote successful maintenance of weight loss.[26] Furthermore, despite the evidence that self-regulation of diet, weight, and PA is beneficial, Hahn et al. describe its negative effects on mental health. They advised careful consideration of the possible negative psychological and emotional effects that regular self-weighing can have on patients before recommending self-monitoring.[21][27] Clinicians should balance the risk and benefit of self-monitoring and consult psychiatric or behavioral specialists if there are concerns over the effects of self-monitoring on patient mental health.

Clinical Significance

High levels of PA have been shown to significantly improve maintenance of weight loss in patients with obesity or who are overweight. However, the clinical application of this fact is significantly more complex. Patients should be counseled that >250 minutes of exercise a week, in addition to calorie restriction, will help maintain weight loss.[14] However, this does not mean that the patients will adhere to this exercise program. Consistent and realistic counseling from medical, nursing, and allied health professionals involved will help patients understand the importance of sustained PA levels in weight loss maintenance. The use of weight maintenance support groups, behavioral and nutrition counseling have all been shown to promote weight loss maintenance and adherence to exercise and diet programs.[21][28]

Increased self-monitoring and patient responsibility are good predictors of adherence to PA programs and weight loss maintenance.[17][21][28] Therefore, clinicians should encourage patients to monitor their diet and exercise and attempt to recognize when they are not meeting their goals to seek further help.[28] However, careful consideration is required due to the risk of worsening mental health and the development of eating disorders.[27]

Enhancing Healthcare Team Outcomes

Maintenance of weight loss in patients with obesity or who are overweight remains a difficult objective. Clinicians should utilize a multidisciplinary approach to gain maximum benefit for the patient. Treatment should involve input from medical, nutrition, and physical therapy experts to provide detailed and patient-oriented PA and diet plans.[14][21] Referral to behavioral specialists is essential for patients who demonstrate binge eating or body dysmorphia and recommended for all patients who have difficulty maintaining sustainable PA and diet programs.[9] 

In cases where weight loss maintenance has been unsuccessful with diet and exercise plans, referral for assessment of bariatric surgery may be appropriate.[14] Prompt and optimal treatment of concordant medical problems, such as musculoskeletal injury, diabetes mellitus, and hypertension, is essential to allow patients to remain fit enough to maintain PA and diet programs. Physical therapy support may be required to assist patients in undertaking suitable PA programs.[14][21] The involvement of multiple interprofessional healthcare team members will result in better results in patients seeking to lose weight and maintain those losses. [Level5]

Increased PA has been shown to improve weight loss and maintenance of weight loss when combined with calorie restriction.[17][18] However, studies examining weight loss maintenance have significant limitations, including poor adherence to exercise programs and subjective or patient-led assessment of program adherence.[19][20]

Little evidence from well-designed randomized controlled trials shows PA will promote maintenance of weight loss independently of calorie restriction. However, several prospective cohort studies have produced results that indicate PA is beneficial in weight loss maintenance.[15][16] As a result, the American College of Sports Medicine recommends >250 minutes of PA per week to promote weight loss maintenance.[14]

Nursing, Allied Health, and Interprofessional Team Interventions

PA is effective in promoting weight loss maintenance in patients with obesity or who are overweight. However, maintaining patient adherence and commitment to PA programs alongside calorie restriction programs requires consistent input from a multidisciplinary healthcare team. Consistent, realistic counseling from medical, nursing and allied health professionals is the best way to avoid unrealistic patient expectations and resulting disillusionment and lack of adherence. Early involvement of behavioral and eating disorder specialists, motivational interviewing, and physical therapy assessment has been shown to promote weight loss maintenance.

Maintaining weight loss in patients with obesity or who are overweight has been repeatedly demonstrated as extremely difficult. This is compounded by both the physiological response from the body to calorie restriction and the physical and mental effort required to maintain sustained PA and diet programs. Therefore, a consistent, combined, multidisciplinary approach is required to give patients the optimum support to maintain weight loss.