***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Overweight and obesity affects more than 66 % of the adult population and is associated with a variety of chronic diseases . Weight reduction reduces health risks associated with chronic diseases and is therefore encouraged by major health agencies . Guidelines of the National Heart , Lung , and Blood Institute ( NHLBI ) encourage a 10 % reduction in weight , although considerable literature indicates reduction in health risk with 3 % to 5 % reduction in weight . Physical activity ( PA ) is recommended as a component of weight management for prevention of weight gain , for weight loss , and for prevention of weight regain after weight loss . In 2001 , the American College of Sports Medicine ( ACSM ) published a Position St and that recommended a minimum of 150 min wk(-1 ) of moderate-intensity PA for overweight and obese adults to improve health ; however , 200 - 300 min wk(-1 ) was recommended for long-term weight loss . More recent evidence has supported this recommendation and has indicated more PA may be necessary to prevent weight regain after weight loss . To this end , we have reexamined the evidence from 1999 to determine whether there is a level at which PA is effective for prevention of weight gain , for weight loss , and prevention of weight regain . Evidence supports moderate-intensity PA between 150 and 250 min wk(-1 ) to be effective to prevent weight gain .  Moderate-intensity PA between 150 and 250 min wk(-1 ) will provide only modest weight loss . Greater amounts of PA ( > 250 min wk(-1 ) ) have been associated with clinical ly significant weight loss .  Moderate-intensity PA between 150 and 250 min wk(-1 ) will improve weight loss in studies that use moderate diet restriction but not severe diet restriction . Cross-sectional and prospect i ve studies indicate that after weight loss , weight maintenance is improved with PA > 250 min wk(-1 ) . However , no evidence from well- design ed r and omized controlled trials exists to judge the effectiveness of PA for prevention of weight regain after weight loss .  Resistance training does not enhance weight loss but may increase fat-free mass and increase loss of fat mass and is associated with reductions in health risk . Existing evidence indicates that endurance PA or resistance training without weight loss improves health risk . There is inadequate evidence to determine whether PA prevents or attenuates detrimental changes in chronic disease risk during weight gain OBJECTIVE Fat oxidation during exercise depends on nutritional state , and exercise performed in the post-absorptive state oxidizes more fat than that performed in the postpr and ial state . However , the effects of exercise on energy metabolism continue during the post-exercise period , and the difference in fat oxidation during exercise may be compensated for during the post-exercise period . The present study compared the effects of an acute exercise bout in the post-absorptive or postpr and ial state on 24 h fat oxidation . METHODS Twelve young male athletes stayed twice in a room-size metabolic chamber for 24 h indirect calorimetry in a r and omized repeated-measure design . Before or after breakfast , i.e. in the post-absorptive or postpr and ial state , subjects exercised at 50 % VO(2)max for 60 min . RESULTS During the 60 min of exercise , energy expenditure in the two exercise trials were equivalent , but exercise in the post-absorptive state was performed with lower RQ compared with that in the postpr and ial state ( P<0.01 ) . The time of exercise relative to breakfast did not affect 24 h energy expenditure ( P>0.5 ) . However , accumulated 24 h fat oxidation was higher ( P<0.05 ) and that of carbohydrate oxidation was lower ( P<0.05 ) when exercise was performed in the post-absorptive state . CONCLUSIONS Compared with exercise performed in the postpr and ial state , exercise performed in the post-absorptive state oxidized more fat and saved more carbohydrate in the body , without affecting 24 h energy expenditure The glycaemic index ( GI ) concept was originally introduced to classify different sources of carbohydrate (CHO)-rich foods , usually having an energy content of > 80 % from CHO , to their effect on post-meal glycaemia . It was assumed to apply to foods that primarily deliver available CHO , causing hyperglycaemia . Low-GI foods were classified as being digested and absorbed slowly and high-GI foods as being rapidly digested and absorbed , result ing in different glycaemic responses . Low-GI foods were found to induce benefits on certain risk factors for CVD and diabetes . Accordingly it has been proposed that GI classification of foods and drinks could be useful to help consumers make ' healthy food choices ' within specific food groups . Classification of foods according to their impact on blood glucose responses requires a st and ardised way of measuring such responses . The present review discusses the most relevant method ological considerations and highlights specific recommendations regarding number of subjects , sex , subject status , inclusion and exclusion criteria , pre-test conditions , CHO test dose , blood sampling procedures , sampling times , test r and omisation and calculation of glycaemic response area under the curve . All together , these technical recommendations will help to implement or reinforce measurement of GI in laboratories and help to ensure quality of results . Since there is current international interest in alternative ways of expressing glycaemic responses to foods , some of these methods are discussed The purpose of this study was to determine the effects of a pre-exercise meal on the plasma human growth hormone ( hGH ) response and fat oxidation during walking . Subjects ( n=8 ) were r and omly provided with either 1 g/kg body weight of glucose in 200 mL water ( CHO ) or 200 mL water alone ( CON ) 30 min prior to exercise and subsequently walked on a treadmill at 50 % of VO2max for 60 min . Plasma hGH concentrations were significantly higher in subjects who received CHO compared to those who received CON at 15 and 30 min . The fat oxidation rate in the CHO was significantly lower than the CON while walking for 5~15 , 25~35 and 45~55 min . Plasma FFA levels were also significantly lower in the CHO compared to the CON at 30 , 45 and 60 min . Plasma glucose levels in the CHO were significantly lower while plasma insulin levels were significantly higher than in the CON at 15 and 30 min . Therefore , the results of this study suggest that the elevation of plasma hGH levels due to the intake of a pre-exercise meal may not be strongly related to fat oxidation and plasma free fatty acid ( FFA ) levels during low-intensity exercise The present study was undertaken to examine the effects of glucose ingestion before exercise on liver glucose output and muscle glucose uptake during exercise . On two occasions , at least 1 wk apart , six trained men ( peak pulmonary O2 uptake = 5.11 + /- 0.17 l/min ) ingested 400 ml of a solution containing either 75 g glucose [ carbohydrate ( CHO ) ] or a sweet placebo [ control ( Con ) ] 30 min before 60 min of exercise at 71 + /- 1 % peak pulmonary O2 uptake . Glucose kinetics ( rates of appearance and disappearance ) were measured by a primed continuous infusion of [6,6 - 2H2]glucose . Liver glucose output was derived from total glucose appearance and the appearance of ingested glucose from the gut . After glucose ingestion , plasma glucose increased to 6.4 + /- 0.4 mmol/l immediately before exercise , fell to 4.2 + /- 0.5 mmol/l after 20 min of exercise , and then increased to a higher value than in the Con group ( 5.4 + /- 0.3 vs. 4.7 + /- 0.1 mmol/l ; P < 0.05 ) after 60 min of exercise . In the CHO group , plasma insulin was higher immediately before exercise ( P < 0.05 ) and , despite falling during exercise , remained higher than in the Con group after 60 min of exercise ( 57.0 + /- 11.4 vs. 24.8 + /- 1.7 pmol/l ; P < 0.05 ) . The rapid fall in plasma glucose in the CHO group was the result of a higher muscle glucose uptake with the onset of exercise ( P < 0.05 ) , which could not be matched by the glucose rate of appearance . Liver glucose output was decreased by glucose ingestion , and although it increased during the early stages of exercise in the CHO group , it did not rise above the basal values and was reduced by 62 % over the 60 min of exercise compared with the Con group . In summary , preexercise glucose ingestion results in increased muscle glucose uptake and reduced liver glucose output during exercise BACKGROUND Obesity is a major health problem due , in part , to physical inactivity . The amount of activity needed to prevent weight gain is unknown . OBJECTIVE To determine the effects of different amounts and intensities of exercise training . DESIGN R and omized controlled trial ( February 1999-July 2002 ) . SETTING AND PARTICIPANTS Sedentary , overweight men and women ( aged 40 - 65 years ) with mild to moderate dyslipidemia were recruited from Durham , NC , and surrounding communities . INTERVENTIONS Eight-month exercise program with 3 groups : ( 1 ) high amount/vigorous intensity ( calorically equivalent to approximately 20 miles [ 32.0 km ] of jogging per week at 65%-80 % peak oxygen consumption ) ; ( 2 ) low amount/vigorous intensity ( equivalent to approximately 12 miles [ 19.2 km ] of jogging per week at 65%-80 % ) , and ( 3 ) low amount/moderate intensity ( equivalent to approximately 12 miles [ 19.2 km ] of walking per week at 40%-55 % ) . Subjects were counseled not to change their diet and were encouraged to maintain body weight . MAIN OUTCOME MEASURES Body weight , body composition ( via skinfolds ) , and waist circumference . RESULTS Of 302 subjects screened , 182 met criteria and were r and omized and 120 completed the study . There was a significant ( P<.05 ) dose-response relationship between amount of exercise and amount of weight loss and fat mass loss . The high-amount/vigorous-intensity group lost significantly more body mass ( in mean [ SD ] kilograms ) and fat mass ( in mean [ SD ] kilograms ) ( -2.9 [ 2.8 ] and -4.8 [ 3.0 ] , respectively ) than the low-amount/moderate-intensity group ( -0.9 [ 1.8 ] and -2.0 [ 2.6 ] , respectively ) , the low-amount/vigorous-intensity group ( -0.6 [ 2.0 ] and -2.5 [ 3.4 ] , respectively ) , and the controls ( + 1.0 [ 2.1 ] and + 0.4 [ 3.0 ] , respectively ) . Both low-amount groups had significantly greater improvements than controls but were not different from each other . Compared with controls , all exercise groups significantly decreased abdominal , minimal waist , and hip circumference measurements . There were no significant changes in dietary intake for any group . CONCLUSIONS In nondieting , overweight subjects , the controls gained weight , both low-amount exercise groups lost weight and fat , and the high-amount group lost more of each in a dose-response manner . These findings strongly suggest that , absent changes in diet , a higher amount of activity is necessary for weight maintenance and that the positive caloric imbalance observed in the overweight controls is small and can be reversed by a modest amount of exercise . Most individuals can accomplish this by walking 30 minutes every day The oxidation of glucose and fructose ingested during moderate exercise performed on a cycle ergometer ( 120 min , 52 % VO2max ) was compared in ten young males fasted ( n = 5 ) or fed ( n = 5 ) before exercise . The subjects ingested r and omly 1.33 g/kg body weight ( approximately 96 + /- 9 g ) of either enriched 13C-glucose ( G ) , 13C-fructose ( F ) , or water only ( W ) ; the solutions were evenly distributed over the exercise period . The fasted subjects began the three exercises with a lower blood glucose ( P less than or equal to 0.05 for F only ) and insulin ( P less than or equal to 0.05 ) levels and a higher free fatty acid ( FFA ) concentration ( P less than or equal to 0.05 ) than the fed ones . Throughout the exercise period , blood glucose level was maintained in fasted as well as in fed group for G and F ingestions , while it decreased ( P less than or equal to 0.05 at the 100th min in fasted subjects ) with water ingestion . Insulin level was similar in both fed and fasted conditions with F and W ingestions and lower than G trials for the fed subjects . For the three ingestions , FFA was lower ( P less than or equal to 0.05 ) in the fasted than in the fed group over the exercise period . Over the 2-h period of exercise , a greater ( P less than or equal to 0.05 ) amount of exogenous F was oxidized in the fasted ( 49 + /- 6 g ) than in the fed ( 36 + /- 5 g ) group , which represent 31 % and 20 % of the total carbohydrate energy supply , respectively . ( ABSTRACT TRUNCATED AT 250 WORDS Skeletal muscle insulin resistance entails dysregulation of both glucose and fatty acid metabolism . This study examined whether a 
    Output:
    
We conclude that aerobic exercise performed in the fasted state induces higher fat oxidation than exercise performed in the fed state