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Establishment of an exercise dose-response outcome for weight loss in obese and overweight adults by Martin Krause, May 2003
Obesity and overweight is a significant public health problem leading to chronic diseases and health conditions such as heart disease and diabetes (Jakicic, Clark, Coleman, Donnelly, Foreyt, Melanson, Volek, Volpe 2001). Therefore, weight loss may be an important consideration in reducing these morbidity factors. This paper defined 2000Kcal/week energy expenditure, through exercise, as a minimum dose to effect significant weight loss. Importantly, the convenience of exercise as well as lifestyle behavioural modification were shown to improve long term exercise adherence. Background
Figure 1: Previous dosage used by various researchers to compare weight loss through exercise in obese, dyslipidemic and overweight adult males and females (source: Ross, Freeman and Janssen (2000)). Several investigators have demonstrated weight loss through energy expenditure (figure 1). However, these investigators concluded that dietary restriction was more conducive to weight loss than exercise prescription. Yet several research methodological errors occurred. These included a vast mismatch in the calorific energy restriction through diet compared with energy expenditure through exercise in all except the 2 investigations of Ross et al (2000) and Sopko et al (1985). In one case the diet restriction of 1200Kcal/day was compared with the energy expenditure of 245Kcal (Schwartz 1987). Another example of mismatch were in the comparative investigations of Hagan et al (1986) where the overweight women and men had a diet restriction of 945Kcal/day and 1705Kcal/day respectively, compared with 190Kcal/day and 255Kcal/day energy expenditure in the exercise groups respectively. In fact, with the two exceptions mentioned, the average calorific deficit induced by exercise was 28% of the calorific shortfall induced by diet. Needless to say the majority of investigators concluded that weight loss through dietary calorific restriction was more efficacious than weight loss through exercise. Thereby, these investigators concluded the superiority of diet over an exercise regime. Furthermore, lack of adherence to exercise was suggested as the problem. However, analysis of these results demonstrate that, even with 100% adherence, approximately 50% more weight should have been lost than was actually lost regardless of intervention regime. Therefore, Ross, Freeman and Janssen (2000) concluded that no justification can be made for the non-inclusion of exercise into any weight loss programme. Importantly, the inclusion of investigations to determine effective exercise dose based on calorific expenditure requires a methodology, which monitors the confounding variable of calorific dietary consumption.
Figure 2: Weight loss through energy expenditure from exercise. Interestingly, despite the methodological problems described, the importance of calorific metabolic energy expenditure for weight loss can be seen (figure 2). The majority of investigators used an average exercise duration of 22.75 minutes. However, 2 groups of researchers account for the calorific outliers by using 43 minutes (Ross et al 2000) and 65 minutes (Sopko et al 1985) exercise durations. Apparently, longer periods of exercise resulted in greater calorific energy expenditure. More precisely, 700Kcal energy expenditure requires that subjects walk on a treadmill for about 60 minutes at 70% of maximal heart rate (~60%V o2max ) (Kraemer, Volek, Clark, Gordon, Puhl, Koziris, McBride, Triplett McBride, Putukian, Newton, Haekkinen, Bush and Sebastianelli 1999).
Figure 3: Fat loss through energy expenditure from exercise A similar trend to figure 2 can be seen in figure 3 whereby greater exercise duration results in greater fat loss. Interestingly, the 700Kcal/day dose resulted in a 6.1kg fat loss, whereas the weight loss was 7.5kg. An MRI analysis of the composition of weight loss revealed comparatively greater visceral and subcutaneous fat loss through exercise than with diet (figure 4). Significantly, several investigators have demonstrated that reductions of visceral fat, reduces insulin resistance in men (Janssen, Fortier, Hudson, Ross 2002; Ross, Dagnone, Jones, Smith, Paddags, Hudson, Janssen 2000; Ross 2003). Therefore, these results suggest that the quality of weight loss may be more conducive to reduction in co-morbidity factors through exercise than dietary calorific restriction alone.
Figure 4: Comparative weight loss composition between dietary caloric restriction and calorific expenditure through exercise (Ross et al 2000). Selection of papers to justify an exercise dose for a weight loss response outcome A large range of energy expenditure over varying time periods, have been used to investigate the effects of exercise on weight loss. Mayo, Grantham and Balasekaran (2003) used 30 obese male army recruits on a 4 month training programme. Kraemer et al (1999) used 35 overweight men on a 12 week programme. Ross et al (2000) used 52 obese men over a 12 week programme. Andersen, Wadden, Bartlett, Zemel, Verde, Franckowiak (1999) used 40 obese women on a 16 week programme with a 1 year follow up. Interestingly, this study demonstrated significant maintenance of weight loss at the 1year follow-up by including a lifestyle behavioural approach to exercise. This may be a novel method of maintaining exercise adherence. Jakicic, Winters, Lang, and Wing (1999) also addressed the problem of exercise adherence by including an 18 month behavioural weight loss programme to 3 different exercise groups of 148 overweight females. These investigations generally used subjects in their 20's and 30's. However, the investigation by Irwin, Yutaka, Ulrich, Bowen, Rudolph, Schwartz, Yukawa, Aiello, Potter, McTiernan (2003) selected a group of 173 overweight post menopausal women to undertake a 12 month exercise trial. This exercise group undertook moderately intense sports/recreational activity, which most frequently included 176min/wk of walking. Conversion tables were used to calculate an average 600Kcal/wk of energy expenditure. All except the investigation of Mayo et al (2003) used randomized control design for assigning subjects into various comparative groups. Instead, Mayo et al (2003) used a non-recruit population matched for age and anthropometric characteristics. These investigations were chosen due to
Importantly, “overweight” was defined as >=24kgm2 BMI by Irwin et al (2003), body weights 20%-70% higher than ideal body weight by Jakicic et al (1999) and BMI = 32.8kgm2 by Kakicic et al (1999) suggesting that weight loss through exercise programmes can be used across a population of people with overweight or obesity problems. Finally, with the exception of Mayo et al (2003) whose subjects used the army canteen, all the investigations chosen had strict dietary controls.
Figure 5: Exercise prescription based on calorific dose.
Figure 6: Duration of continuous activity for 300Kcal energy expenditure in a 200lb adult (source Jakicic et al 2001). Tabulated data provided by the ACSM working group (Jakicic et al 2001) demonstrates the minutes of exercise required for 300Kcal of energy expenditure for adults with a body weight of 200lbs during various activities (figure 6). Interested readers should refer to the original table for other body weight comparisons. Importantly, exercise duration and intensity can be prescribed, which can be converted into energy expenditure. However, both duration and intensity may be considered as inverse dose characteristics. For example, an energy expenditure of 700Kcal/day, 3 days per week, appears to be sufficient to reduce weight and improve insulin sensitivity (Jakicic et al 2001). Alternatively, this would require a lesser intensity of 1 hour walking at 2.5m.p.h (4km/hr), 7 days per week. Interestingly, lap swimming burns more calories sooner, suggesting that non-weight bearing activities may result in greater exercise intensity.
Figure 7: Energy expenditure through exercise versus weight loss. A threshold in the vicinity of 2000Kcal/wk is sufficient to reduce weight, yet greater energy expenditure leads to greater weight and fat loss (figure 7 & 8). Although the average drop-out rates were low in these investigations, problems with exercise adherence are conceivable if the weekly programme takes too long.
Figure 8: Fat mass loss post exercise vs energy expenditure
Figure 9: Fat free mass (FFM) loss post exercise vs energy expenditure The least fat free mass (FFM) loss occurred in the group of young army recruits whose exercise adherence was not based on voluntary effort. The outliers in figures 7, 8 and 9 represented army recruits whose training regime time totaled 446 hours in 16 weeks (average ~ 4 hours/day). The young age of these subjects may account for the lack of FFM loss. These investigators demonstrated a FFM loss only occurred with weight reductions exceeding ~11kg (Mayo et al 2003).
Figure 10: Reduction in waist girth demonstrated by Jakicic et al (1999), Mayo et al (2003), Ross et al (2000) Excess fat deposition in the abdomen region is a stronger predictor of cardiovascular disease and type II diabetes than is obesity per se (Blair, Kohl, Barlow, Paffenbarger, Gibbons, Marcera 1995; Ross 2003). Indeed, the reduction in waist circumference with the 700Kcal/day exercise prescription resulted in improved insulin sensitivity in obese men (Ross et al 2000). Again, the army recruits demonstrated greatest change through greater energy expenditure. Exercise programme adherence and long term outcomes The previous investigations demonstrate significant weight loss in response to exercise which uses at least 2000Kcal energy expenditure per week. Importantly, a behavioural lifestyle intervention is recommended, as improvement gains after a 16 week exercise intervention programme were maintained at a 1 year post exercise follow-up (Andersen et al 1999). Irwin et al (2003) used a similar behavioural lifestyle intervention with success over 12 months, however no follow-up data was provided. Jakicic et al (1999) measured the adherence to their behavioural lifestyle and exercise programme during an 18 months trial. Additionally, they compared 3 exercise groups:
As expected, the greater volume of exercise resulted in greater weight loss (figure 11 & 12). Surprisingly, the SBEQ group did considerably better at 12months (figure 13) suggesting better exercise adherence. Perhaps the novelty and convenience of the treadmill may have improved the motivation, comfort and convenience to exercise. Similar to the observation made with the energy consumption during swimming, it may be the comfort of the shock absorbing characteristics of the treadmill, which is an important consideration in overweight and obese people. Alternatively, the pacing characteristics of the treadmill and lap swimming may be a motivating factor to attain an exercise goal, which more closely resembles the energy expenditure required to lose weight.
Figure 11: weight loss based on volume of exercise (min/wk). The greater volume of exercise resulted in greater weight loss
Figure 12: Energy expenditure per week vs weight loss. The greater the energy expenditure, the greater the weight loss
Figure 13: Comparative weight loss between exercising groups. Convenience of exercise appeared to be an important factor in exercise adherence and weight loss. The multiple short bout group using a treadmill had greater weight loss than the equivalent multiple short bout group without a treadmill Implications of research to health outcome A body mass index (BMI) > 25kg/m2 is considered to represent a significant health risk including diabetes and cardiovascular disease (Shaper, Wannamethee, Walker 1997). Although these results did not result in BMI <25kg/m2, at 6 months there was a positive trend in that direction in this population of overweight women aged between 25 and 45. However, this trend began to reverse after 6 months (figure 14). The investigators correlated this reversal in trend to a loss of adherence to the exercise programmes. Importantly, these results highlight the need for convenience when prescribing an exercise regime to the overweight – obese population.
Figure 14: Reductions in Body Mass Index (BMI) at 6, 12 and 18 months. In other investigations, high intensity exercise (RPE 15.4) versus low intensity exercise (RPE 11.1) for a 16 week walking programm was shown to reduced regional body fat by 47 vs 11cm2 and abdominal visceral fat content by 24 vs 7cm2 (Irving et al 2008) . Further reductions in visceral fat were reported by the same authors with 8 months of vigorous jogging (~20miles/week). This is significant as visceral fat is directly correlated with the progression of glucose intolerance to type II insulin resistant diabetes. Interestingly, moderate intensity exercise (500Kcal) energy expenditure was shown to improve postprandial dyslipidemia in people diagnosed with metabolic syndrome (Mestek et al 2008). This finding wasn't found in healthy subjects, suggesting that even moderate amounts of activity can have large impacts on a critical risk factor for morbidity. Risk factors associated with exercise Certain significant risk factors do exists when prescribing exercise to people who are by definition overweight – obese. These include the co-morbidity conditions such as hypoglycaemia in people with diabetes, stroke or heart attack in people with cardiovascular disease. Fortunately, even in exercise regimes without weight loss, serum markers associated with these complications (Sharper et al 1997), such as fat and glucose metabolism were reduced (Duncan, Perri, Theriaque, Hutson, Eckel, Stackpoole 2003). Additional risk reducing changes included reduced systolic blood pressure and increased peak O2 consumption, as well as improved serum cholesterol and triglycerides (Ross et al 1999). However, these changes may take time (e.g. 6 months [Jakicic et al 1999]) and therefore these risk factors need to be monitored and balanced with the potential benefits. Gradual increases in the training regime as described previously are warranted to reduce these risks. Of the 148 subjects who participated in that programme only 6 retired due to medical reasons (Jakicic et al 1999). It has been suggested that exercise resulting in energy deficits > 700Kcal/day may result in lean tissue loss in addition to fat (Mayo et al 2003). However, obese men who expend 700Kcal/day by walking for 12 weeks reduced total fat by 6.1kg with a preservation of skeletal muscle (Ross et al 2000). No significant benefit was demonstrated in regimes, which involved more vigorous resistance training (Andersen et al 1999; Wadden, Vogt, Andersen, Bartlett, Foster, Kuehnel, Wilk, Weinstock, Buckenmeyer, Berkowitz, Steen 1997). Importantly, for sedentary overweight-obese individuals, a diet combined with a lifestyle programme of moderate intensity physical activity can facilitate weight loss, enhance weight management and improve cardiovascular disease profiles (Andersen et al 1999). Therefore, risks may be reduced through progressive incremental increases in the duration of exercise whilst maintaining moderate exercise intensity. Conclusion It would appear that the exercise dose selected has to be commiserated with exercise adherence. The minimal dose required to affect weight loss is in the order of 2000Kcal/wk. Ideally, this would include a regime whereby the individual's lifestyle is not disrupted. Indeed, these investigations suggest that the convenience of the exercise as well as meaningfulness (behavioural modification) to overall health and well - being play an important part in adherence to the exercise programme beyond a 4 month regime. 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