BMI category
Treatment
25–26.9
27–29.9
30–34.9
35–39.9
≥40
Diet, physical activity, and behavior therapy
With comorbidities
With comorbidities
+
+
+
Pharmacotherapy
With comorbidities
+
+
+
Surgery
With comorbidities
In the report [9], the panel described the criteria for a low-calorie diet (LCD): a diet with a caloric restriction of at least 500 kcal comprised of less than 30% total fat with 8–10% total saturated fat, 15% calories as protein, and 55% or more of calories as carbohydrates, primarily as complex carbohydrates. The LCD contains less than 300 mg per day of cholesterol, no more than 100 mmol per day or 6 g of sodium chloride, 20–30 g of fiber, and 1,000–1,500 mg per day of calcium. The report suggests avoiding the use of very low-calorie diets (VLCD), that is, diets containing less than 800 kcal per day for routine weight loss. The panel noted that use of the VLCD should be restricted to specific conditions and with monitoring by a physician. In general, The Practical Guide stated that a caloric intake of 1,000–1,200 kcal per day is appropriate for most women. For men, and for women whose weight is greater than 165 lb or who exercise, a caloric intake of 1,200–1,600 kcal per day may be needed. However, since 1998, numerous weight-loss diet strategies have been published and reviewed [12].
Specific dietary interventions for weight loss include VLCD [13–19], balanced deficit diets (BDDs), LCDs, and meal replacements options that are not routinely prescribed in clinical practices (and thus not covered in this review). The most common alterations in macronutrient composition to achieve the desired caloric deficits include low-fat diets, low-carbohydrate diets, high-protein diets, or combinations of the above. Recent studies have also examined the effects of the glycemic index versus the glycemic load of various eating plans. Please see Fig. 3.1 for a list of common diets and their macronutrient composition.
Fig. 3.1
Nutrient percentage of diets comparison (Reproduced from Jeanette Newton K, Lori R. Medical weight control in the adult patient. Nutritional and clinical management of chronic conditions and diseases. CRC Press; 2005, with permission). LC/HF low carbohydrate/high fat; ProPower Power; S Beach South Beach; S Busters Sugar Busters; NIM National Institute of Medicine The Practical Guide; FGP 2000 Food Guide Pyramid; Wt W Weight Watchers; S Sutton Seattle Sutton’s Healthy Eating; C to Lose choose to lose weight loss/healthy eating plan
Very Low-Calorie Diets
As noted above, VLCDs contain about 800 kcal per day, with protein as the major macronutrient component. The higher protein intake leads to the differential breakdown and utilization of body fat stores while sparing muscle and other protein stores [20]. The calorie-restricted, protein-sparing modified fast typically uses commercially prepared formulas to promote rapid weight loss under medical supervision. The formulas consist of shakes, bars, or soups with the predefined calorie content, along with specified vitamins and micronutrients. In certain cases, VLCDs may consist of entirely lean protein foods with limited portions sizes designed to achieve the set calorie amount or a combination of formula and lean protein foods. Examples of popular VLCDs that are commercially available are Optifast, Medifast, NutriMed, HMR (Health Management Resources), the Cambridge diet, and the Health ONE diet (HNT or Health and Nutrition Technology) [13–18]. The HCG program combines injections of the human chorionic gonadotropin hormone with a VLCD to accelerate weight loss without the reduction in metabolic rate that may be seen with rapid weight loss [19].
The goal of VLCDs is to induce rapid weight loss in patients with a BMI greater than 30 and significant comorbidities or a BMI more than 27 with medical conditions related to being overweight or obese. VLCDs are generally indicated for up to 16 weeks, followed by a refeeding period and a maintenance diet [20]. It should be noted that patients have safely used VLCDs for periods longer than 16 weeks with close medical supervision [21]. The average expected weight loss is 3–5 lb per week with most individuals, and the majority is expected to lose 15–25% of their initial weight in the first 3–6 months. There is a high recidivism rate in the absence of a maintenance program with weight regain at 1 year, leading some investigators to conclude that the long-term maintenance of weight loss following VLCDs may not be superior to weight loss by LCDs [22, 23].
Historically, use of VLCDs was indicated for the medical management of severely obese medical patients [20]. VLCDs are now being employed by some to facilitate weight loss prior to bariatric surgery [24]. The efficacy of preoperative weight loss using VLCDs has been shown to reduce liver size and fat content, improving procedural outcomes, reducing total body weight and waist circumference prior to surgery, and inducing rapid weight loss prior to surgery for those on a supervised inpatient LCD program for the superobese [25–27]. Common minor side effects include, but are not limited to, fatigue, dehydration, hair loss, cold intolerance, constipation, nausea, muscle cramps, and diarrhea. Serious side effects include gallstone formation and rare cardiac arrhythmias [20].
Balanced Deficit Diets
BDD reduce total caloric intake by 500 kcal per day but contain food choices from all food groups with a focus on portion control to promote slow but consistent weight loss [28]. Common eating strategies that are considered BDDs with the appropriate caloric restriction include the Dietary Approach to Stop Hypertension (DASH) eating plan and eating plans that adhere to the recommendations of the 2010 Dietary Food Guidelines [10, 29]. BDDs have demonstrated effectiveness for acute weight loss and long-term maintenance of weight loss [30, 31]. Examples of structured commercially available programs include Weight Watchers, Jenny Craig, Nutrisystem, and the LA Weight Loss Program [32–35]. These programs are being utilized in clinical practices with increasing frequency.
Low-Calorie Diets
Similar to BDDs, LCDs, as described in The Practical Guide, are designed to have a balanced calorie deficit of 500–1,000 kcal to promote weight loss at a rate of 1–2 lb per week [9]. Of significance, while all BDDs are LCDs, not all LCDs are considered BDDs, as specific macronutrients may be overly restricted to achieve caloric reduction.
Low-Fat Diets
Low-fat diets restrict fat intake to less than 25% of total calories [10]. These diets differ with regard to the type of fat present, with a focus on reducing total cholesterol, saturated and trans fat content. The amount of protein varies considerably amongst the different low-fat diets, as does the amount, quantity, and type of carbohydrates.
Low-Carbohydrate Diets
Low-carbohydrate diets limit net carbohydrate intake to 20–100 g per day, as opposed to the Institute of Medicine (IOM), which recommends a minimum of 130 g per day [36]. Examples of low-carbohydrate diets are the Atkins diet, the Zone diet, the South Beach diet, and Protein Power [37–40]. These diets differ with regard to the amount and type of carbohydrates allowed, as well as the amount of fat consumed. Importantly, many low-carbohydrate diets treat all carbohydrates as the same. Other meal plans such as the low-GI diet, The New Atkins for a New You, the South Beach diet, and Sugar Busters incorporate the concept of glycemic index and glycemic load [37, 39, 41, 42]. Carbohydrates are selected based on how they affect the body’s glucose level. Carbohydrates that break down slower and gradually release glucose into the blood stream have a low glycemic index, whereas those that result in a rapid rise in blood glucose have a high glycemic index. In the original publication by Jenkins et al. [43], foods with a low glycemic index were associated with improved postprandial hyperglycemia in diabetics. High glycemic index foods are appropriate for recovery after endurance exercise and for the treatment of hypoglycemia [44]. The glycemic load, in contrast, is the ranking system for the carbohydrate content in specific food portions based on their glycemic index and portion size in the context of a meal. The measure is used to determine the quality and quantity of carbohydrates that predict optimal glucose control but has limited clinical applicability in weight-loss efforts [45].
High-Protein Diets
Current Recommendations
As clinicians, specific diet recommendations are requested by and for patients who desire weight loss. Clinicians are often faced with setting realistic weight-loss goals for and with patients. Weight loss of 5–15% has been shown to significantly reduce obesity-related complications [48] and serves as a benchmark of success for medical weight-loss programs [49]. While there is little disagreement about the negative consequences of being overweight and obese, there remains great debate over the effectiveness of treatment strategies, particularly in relation to the optimal weight-loss diet [50–71].
In 2009, four diets were compared to determine the optimal diet for weight loss and weight maintenance [72]. While all of the diets were energy-reduced to facilitate weight loss, they differed significantly in how the calorie reduction was achieved. The components of these diets are shown in Table 3.2.
Table 3.2
Four diet comparisons to determine the optimal diet for weight loss and weight maintenance
Type | Fat (%) | Protein (%) | Carbohydrate (%) |
|---|---|---|---|
Low fat, average protein | 20 | 15 | 65 |
Low fat, high protein | 20 | 25 | 55 |
High fat, average protein | 40 | 15 | 45 |
High fat, high protein | 40 | 25 | 35 |
The authors found no differences in outcome or weight loss at 24 months regardless of diet composition. Reports by other investigators find similar outcomes at 36 months [73]. However, the sample of more than 800 consisted largely of Caucasian (81%) and college-educated (69%) participants, limiting how applicable the results are to minority and less-educated populations.
In general, a healthy LCD, such as the DASH eating plan, which emphasizes fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products, remains the recommended eating plan of choice. It may include lean meats, poultry, fish, beans, eggs, and nuts. It is low in saturated fats, trans fat, cholesterol, salt (sodium), and added sugars. The DASH trial included minorities and patients with a variety of educational backgrounds and socioeconomic strata, such that the results have broader clinical applications [74]. A vegetarian diet that selects from all food groups except animal products may also be considered a healthy option [10].
Pharmacologic Therapy
Drug therapy for weight management should be limited to use in overweight individuals (BMI greater than 27) with weight-related comorbidities, or the obese (BMI greater than 30), to minimize risk and maximize the benefit of this intervention [9]. It is a useful adjunctive intervention when combined with increased physical activity, as well as dietary and behavior modifications. Given that obesity is a rarely cured chronic disease that requires lifelong intervention, the ideal adjunctive drug therapy should be safe for long-term, if not lifelong, use [9]. However, in general, these drugs are indicated for short-term use, as only three antiobesity drugs (sibutramine, orlistat, and rimonabant) have data regarding long-term safety, ranging from 1 to 4 years [75–77]. In the clinical setting, when diet and lifestyle modifications fail to induce or maintain a weight loss of 10% after 3 months of supervised medical weight management, pharmacological assistance should be considered based on an individual’s risk to benefit ratio [78]. Some investigators report an increased weight loss when antiobesity drugs are combined with a VLCD [79].
Medications currently indicated clinically for short-term use in the treatment of obesity belong to one of seven categories: sympathomimetics, drugs that alter fat metabolism, antidepressants, serotonin receptor agonists, antiepileptic drugs, antidiabetes drugs and polytherapies. In addition, there are three categories of medications that induce weight loss and may be potential drug targets for future clinical practice: dietary supplements, endocannabinoid receptor antagonists, and experimental drugs.
Sympathomimetic
Sibutramine (trade name: Meridia®), originally developed as an antidepressant, is a serotonin and norepinephrine reuptake inhibitor that produces satiety and prevents diet-induced declines in metabolic rate [80, 81]. In a multicenter dose-ranging trial, 1,047 patients were randomly assigned to receive a placebo, or 1, 5, 10, 15, 20, or 30 mg of sibutramine daily for 6 months [82]. Compared to the placebo group that experienced a 1% weight loss, the group receiving the 30 mg dose experienced a 9.5% weight loss. Other subjects also lost weight in a stepwise fashion consistent with dose response. Of note, in the United States, 15 mg is the maximal approved dose. When evaluated for effect after continuous or intermittent use for 48 months and for its ability to maintain long-term weight loss, sibutramine was found to be superior to placebo in effecting weight loss without an increase in cardiovascular events [75, 83].
In February 2010, sibutramine was withdrawn from all European markets following a safety review based on data from the Sibutramine Cardiovascular Outcomes Trial (SCOUT), which enrolled more than 10,000 overweight or obese patients with diabetes or history of coronary artery disease, peripheral vascular disease, or stroke, along with other cardiovascular risk factors [84–86]. An analysis of the trial’s primary end point—a composite of myocardial infarction, stroke, resuscitated cardiac arrest, or death—found the rate to be 11.4% for patients receiving sibutramine and 10% for those receiving placebo. The 2010 review found that the risk for cardiovascular events with sibutramine is significantly increased only in patients with a history of cardiovascular disease (P = 0.023). It was recommended that healthcare professionals should regularly monitor blood pressure and heart rate in patients taking sibutramine. The FDA noted that “if sustained increases in blood pressure and/or heart rate were observed, sibutramine should be discontinued. Additionally, sibutramine should be discontinued in patients who do not lose at least 5% of their baseline body weight within the first 3–6 months of treatment, as continued treatment is unlikely to be effective and exposes the patient to unnecessary risk” [87]. However, due to growing concerns from SCOUT, the FDA and Abbott Pharmaceuticals announced a voluntary withdrawal of sibutramine from the US market [88].
Other drugs in the class with high abuse potential, including phentermine and diethylpropion [89], are recommended for short-term use, whereas phenylpropanolamine, ephedrine, and ephedra alkaloids have been removed from the United States markets due to serious adverse reactions despite effectiveness in short-term weight-loss trials.
Drugs that Alter Fat Absorption
Orlistat (trade name: Xenical®, Alli®) is a potent inhibitor of gastric, carboxylester, and pancreatic lipases, binding approximately 30% of ingested fat calories in the diet, leading to weight loss [90]. Orlistat is more effective than lifestyle changes alone in producing weight loss and is an effective intervention for maintenance of weight loss for up to 4 years [3, 17]. Orlistat is available in 60- and 120-mg capsules with a recommended dosage of three times per day. The most common side effects are gastrointestinal distress associated with fecal seepage typically seen following high-fat ingestion, and a minor reduction in fat-soluble vitamin levels. The concomitant use of a multivitamin separated by at least 2 h from the active medication is recommended [90, 91].
Antidepressants
Three agents in this class have been used for weight-loss therapy: fluoxetine, sertraline, and bupropion [92–94]. Fluoxetine and sertraline are selective serotonin reuptake inhibitors (SSRI), and bupropion is thought to modulate norepinephrine. While these drugs induced weight loss greater than placebo in the first 6 months, weight regain in the next 6 months limits their use for weight management.
Selective Serotonin Receptor Agonists
On June 27, 2012, the FDA approved the release of Lorcaserin for the treatment of obesity [95]. Lorcaserin is a selective agonist for the serotonin (5-hydroxytryptoptamine) 2C receptor. When the receptor is activated, individuals feel full faster when consuming smaller quantities of food leading to a reduction in caloric intake. In three sentinel studies, over 8000 overweight and obese patients with and without diabetes mellitus 2 were treated for 52–104 weeks with lorcaserin [96–98]. The treatment group experienced greater weight loss at one year (3–3.7%) versus placebo. Weight loss of at least 5% was achieved by 47% of non-diabetics and 38% of diabetics as compared to 23% and 16% of their respective controls. Similar to recalled the antiobesity agents, fenfluramine and dexfenfluramine, this medication can cause serotonin syndrome. Therefore, it should not be taken with medications that increase serotonin levels such as certain antidepressants and medications for migraines. In contrast, valvular heart disease does not appear to occur more often than with placebo but long-term safety monitoring is in progress. Initial concerns from animal models regarding an increased risk for breast cancer and brain cancer were diminished following a review of the original animal data and assessment of human clinical trials. To avoid adverse outcomes and minimize risk of complication, if after 12 weeks of therapy, a patient has not lost at least 5% of baseline body weight, the drug should be discontinued. Notably, lorcaserin should be used with caution in congestive heart failure due to an increased number of serotonin 2B receptors in heart failure. The most common side effects in non-diabetics include headache, dizziness, fatigue, nausea, dry mouth, and constipation, and in diabetic patients are low blood sugar (hypoglycemia), headache, back pain, cough, and fatigue. Pregnant women should avoid taking this medication.
Antiepileptic Drugs
Topiramate is an antiepileptic that is also effective in the treatment of migraines. In clinical trials, it was associated with weight loss greater than placebo. Because of its significant side effects, which include metabolic acidosis, it is not recommended for use in general weight management [99, 100].
Zonisamide is an antiepileptic drug that has dopaminergic and serotonergic properties [101]. While it induces weight loss, it is not recommended as independent therapy for weight loss.
Diabetes Drugs
Metformin is a biguanide approved for the treatment of diabetes mellitus that was associated with weight loss greater than placebo leading to 2.5% excess body weight loss in the metformin-treated group of the Diabetes Prevention Trial. While this rate of weight loss is not significant for a weight-loss drug per se, it makes this drug a useful tool when treating overweight diabetics [102].
Newer diabetes agents have been developed based on gut and hormonal physiology. Pramlintide is an amylin agonist. Amylin, also known as islet amyloid polypeptide, is a peptide hormone secreted by the pancreatic cell simultaneously with insulin in response to nutrients. Like amylin, pramlintide slows gastric emptying and improves glycemic control in both type 1 and 2 diabetics. In the studies for glycemic control, pramlintide was associated with modest weight loss. Its use is limited by its subcutaneous route of administration [103, 104].
On the other hand, exenatide is a long-acting synthetic glucagon-like polypeptide-1 (GLP-1). Along with GLP-1, gastric inhibitory polypeptides or glucagons insulin polypeptides (GIP) stimulate glucose-dependent insulin release and are called incretin peptides. In contrast to pramlintide, exenatide is only indicated for use in type 2 diabetes. During intervention studies, modest weight loss improved glycemic control and resulted in further weight loss [105].
Liraglutide, a second generation GLP-1 analogue, was found to be more effective than placebo and orlistat at a dose of 3.0 milligrams in inducing weight loss in non-diabetic adults over a period of 20 weeks [106, 107]. When directly compared with twice daily exenatide, there were fewer side effects and increased tolerance with the once daily dosing of liraglutide [108]. Trials in Europe resulted in its approval for the treatment of both obesity and diabetes [109, 110]. In the United States, it is only approved for the treatment of type 2 diabetes mellitus as it takes significantly higher doses than needed for glycemic control to induce acceptable weight loss. This is a concern for the type I diabetic and non-diabetic obese patients given the risk of hypoglycemia.
Polytherapies
Polytherapy is defined as a combination of agents that are designed to simultaneously target more than one biological mechanism and that might ultimately be more effective in producing sustained weight loss and improvements in co-morbidities [111]. The classic example of an effective polytherapy was the combination of fenfluramine and phentermine. While very effective in producing significant weight loss, the combination drug was withdrawn from the market due to major cardiovascular side effects. In 2010, the FDA considered a fixed drug combination under the trade name, Qnexa [112–114]. However, the pre-clinical trials raised concerns about increased teratogenicity and elevations in resting heart rate. Women that received topiramate during pregnancy were more likely to have infants born with an orofacial cleft defect. Individuals receiving combination therapy also saw an increase in resting heart rate but were noted to have improvements in blood pressure with weight loss. Further, phentermine-topiramate potentially increased the risk of metabolic acidosis, glaucoma, and psychiatric as well as cognitive adverse effects. However, when the overall risk-benefit was considered due to improved health benefits with weight loss, the product, now under the trade name, Qsymia, was re-submitted to the FDA. The fixed dose combination therapy received approved for the treatment of obesity and diabetes 2 in July 2012. Prescribing physicians must be trained, patients must agree to use effective contraception and only certified pharmacies can dispense the medication. Patient selection should be limited to those with an indication for pharmacologic therapy for the treatment of obesity. To minimize adverse outcomes, if the patient has not lost at least 3% of the baseline weight on the phentermine-topiramate 7.5 mg/46mg dose, the drug should be discontinued or the dose increased. The goal is weight loss at the higher dose is at least 5% from the baseline weight after an additional 12 weeks of therapy or the phentermine-topiramate 15mg/92mg dose should be discontinued. Data safety monitoring is ongoing.
Dietary Supplements
Many dietary supplements are reportedly associated with weight loss but have little or no published data to support these conclusions. In 2004, a review of available supplements found that chitosan and guar gum were ineffective for weight loss. There were safety concerns due to the lack of data for Ephedra, elemental calcium, chromium, ginseng, glucomannan, green tea, hydroxycitric acid, carnitine, psyllium, pyruvate supplements, St. John’s wort, Hoodia gordonii, and conjugated linoleic acid [115]. An update review of the dietary supplements is in progress with results anticipated to be published within the next year. Of significance, physicians should be aware that two compounded supplements with reported weight-loss effects are being imported from Brazil. These supplements, Emagrece Sim (also known as the Brazilian diet pill) and Herbathin dietary supplement, have been shown to contain prescription drugs, including amphetamines, benzodiazepines, and fluoxetine [116]. There is an FDA warning against their use in the United States [117].
Future Considerations
Experimental Drugs
The number of drugs or drug combinations being considered for future clinical use reportedly exceeds 150. Therefore, this section will be limited to new drugs or combinations of drugs in each of the recognized categories.
Sympathomimetics
Tesofensine 0.5 mg is a monoamine reuptake inhibitor and, while similar to sibutramine in its pharmacology, results in nearly double the weight loss. However, it also increases blood pressure, heart rate, and worsens associated psychiatric disorders. Other common adverse effects included nausea, dry mouth, abdominal pain, and diarrhea. Controlled trials are in progress outside the United States [119, 120].
Antidepressants
Bupropion and the opioid antagonist, naltrexone, have been combined in a fixed-dose, sustained-release preparation named Contrave, which resulted in 3–7% weight loss in phase III clinical trials in Canada. The combination is thought to increase stimulation of the central melanocortin pathways, resulting in increased energy expenditure and reduced appetite. Additional studies showed benefit, but this combination therapy was denied approval by the FDA in 2011 due to cardiovascular concerns [121, 122]. The manufacturer, Orexegin Therapeutics, must show data that the drug does not increase the risk for myocardial infarction. The Light trial is in progress and it is anticipated that the manufacturer will resubmit the drug for FDA approval [123].
Endocannabinoid Receptors
Peptides
This is a new category for drug therapy targets. Several peptides have been shown to result in weight loss and are now in clinical trials. Recombinant leptin demonstrated a dose response weight-loss pattern and increased fat loss in both obese and lean adults [126]. The gut hormone peptide fragment YY3-36 induced inhibition of food intake in obese adults resulting in weight loss. Further, endogenous peptide YY levels were low in obese participants implicating peptide YY deficiency in the pathophysiology of obesity [127].
Exercise
Exercise and the use of increased energy expenditure have been shown to reduce morbidity and mortality in many disease states [128]. This effect can be seen both in men and women [129]. More precise interpretation of the data demonstrates that energy expenditure may have its greatest effect by improving one’s cardiorespiratory fitness [130]. We know that excess body weight is associated with increased health risk from many chronic medical conditions [131]. Healthcare improvements with exercise have been demonstrated not only in patients with a normal BMI but also in those who are overweight or obese [132].
We know that excess body weight is a result of an energy imbalance, meaning that more calories are taken in than are used. Thus, weight loss can be as a direct result of increased energy expenditure as long as there is not a parallel and similar increase in caloric intake. One theory divides energy expenditure up into three components: resting energy expenditure (REE), thermic effect of food (TEM), and energy expenditure from physical activity (EEPA). Tatarrani et al. noted that in sedentary adults, REE is often from 60 to 70%, while TEE is often 10% [133]. In contrast, EEPA is highly variable amongst individuals and provides the best opportunity to increase overall energy consumption. This provides the rationale of why targeting a patient’s EEPA may ultimately have a reasonable impact on his or her overall weight.
Monitoring exercise in human studies of weight loss is unfortunately very difficult, as we often rely on a global self-reported index [134]. Few people can actually document how far they walk on a given day. To demonstrate this problem, the Health Survey of England (HSE) published information based on data collected between 1997 and 2003. This data noted an increased number of individuals achieving a minimum physical activity target of 30 min of moderate-intensity activity 5 days a week [135]. However, at the same time there was a startling increase in obesity reported in the United Kingdom bringing into question the reliability of these voluntarily recorded exercise values. However, we do have very good proxy knowledge of a reduction in exercise in the industrialized nations since the 1960s. This is a result of a number of lifestyle changes, including an explosion in second car homes, increased use of labor-saving devices, increased television viewing, reduction in walking amongst children, and major reductions in those employed in farming and manufacturing [136].
Setting exact exercise goals for weight loss must be individualized. In general, when individuals lose 5–10% of their baseline body weight, there is a substantial reduction in health risk. In order to achieve that goal, an individual must exercise at a level to expend at least 200 kcal per day, which correlates to brisk walking 5 days a week for approximately 45 min per day [137].
Guidelines regarding exercise and physical activity can be very confusing. In 1995, the American College of Sports Medicine (ACSM) recommended that sedentary adults accumulate 30 min or more of moderate-intensity exercise most days of the week [138]. These recommendations were followed by similar recommendations from the United States Surgeon General and the National Institute of Health in 1996 [139]. However, the concurrent rapid increase in obesity rates led many to question these values. In 2001, the ACSM recommended that to lose weight, individuals should have moderate-intensity exercise for 150 min per week and strive for 200 min per week. The ACSM further stated that the impact of moderate-intensity exercise for 200–300 min per week would result in even greater weight loss but was probably unrealistic for many people to adopt and maintain [140]. In 2002, the IOM recommended that individuals spend 60 min per day on moderate-intensity exercise for weight maintenance [141]. In 2003, the International Association for the Study of Obesity (IASO) made two recommendations: for formerly obese individuals, they recommended 60–90 min of moderate-intensity exercise per day to prevent weight regain. They also stated that 45–60 min of moderate-intensity exercise per day was required to prevent an overweight individual from becoming obese [142]. Data from the National Weight Control Registry (NWCR) supports the idea that a large amount of exercise is necessary to maintain weight loss. They reported that successful weight loss is maintained by individuals who expend 11,830 kJ per week through exercise, equivalent to walking 28 miles per week [143]. In 2007, the ACSM released updated guidelines similar to their initial guidelines recommending 30 min per day of moderate activity to prevent weight gain. For those individuals gaining weight at this activity level, exercise time periods should be slowly increased. These same guidelines are supported by the American Heart Association (AHA) [144]. Table 3.3 provides an average calorie utilization for activities performed for 30 min.
Table 3.3
Moderate exercise and calories expended at 30 min
Stretching—90 |
Light weights—110 |
Low-impact aerobics—110 |
Cleaning house—120 |
Pushing a stroller—120 |
Bowling—120 |
Child care—120 |
Slow walking—140 |
Slow bicycling—145 |
Raking—160 |
Golf walking with clubs—170 |
Baseball—180 |
Painting, plastering—180 |
Hiking—190 |
Dancing—200 |
Heavy yard work—220 |
Rapid walking—230 |
Moderate/heavy weight lifting—230 |
Shoveling snow—230 |
Treadmill—240 |
Tennis—240 |
Basketball—260 |
Swimming—260 |
High-impact aerobics—280 |
Backpacking—280
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