***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: Background Low-fat ( LF ) and high-fat ( HF ) weight loss diets improve brachial artery flow-mediated dilation ( FMD ) in obese individuals , although results are conflicting . Moreover , the role that adipose tissue plays in mediating these diet-related effects are unknown . Objective This study examined how modulations in FMD by HF and LF diets relate to changes in adipocyte parameters . Design Obese subjects ( n = 17 ) were r and omized to a HF diet ( 60 % kcal as fat ) or a LF diet ( 25 % kcal as fat ) for 6 weeks . Both groups were restricted by 25 % of energy needs . Results Body weight decreased ( P < 0.05 ) in both groups ( HF : -6.6 ± 0.5 kg , LF : -4.7 ± 0.6 kg ) . Fat mass and waist circumference were reduced ( P < 0.05 ) in the LF group only ( -4.4 ± 0.3 kg ; -3.6 ± 0.8 cm , respectively ) . FMD improved ( P < 0.05 ) in the LF group ( 7.4 ± 0.8 % to 9.8 ± 0.8 ; 32 % increase ) and was impaired in the HF group ( 8.5 ± 0.6 % to 6.9 ± 0.7 ; 19 % reduction ) . Increases in plasma adiponectin ( P < 0.05 , 16 ± 5 % ) , and decreases in resistin ( P < 0.05 , -26 ± 11 % ) , were shown by the LF diet only . Greater decreases in leptin were observed with LF ( -48 ± 9 % ) versus HF ( -28 ± 12 % ) ( P < 0.05 , diet × time ) . Increased FMD by the LF diet was associated with increased adiponectin , and decreased fat mass , waist circumference , leptin , and resistin . Conclusion Beneficial modulations in vascular health by LF diets may be mediated by improvements in adipocyte parameters CONTEXT Obesity in the United States has increased dramatically during the past several decades . There is debate about optimum calorie balance for prevention of weight gain , and proponents of some low-carbohydrate diet regimens have suggested that the increasing obesity may be attributed , in part , to low-fat , high-carbohydrate diets . OBJECTIVES To report data on body weight in a long-term , low-fat diet trial for which the primary end points were breast and colorectal cancer and to examine the relationships between weight changes and changes in dietary components . DESIGN , SETTING , AND PARTICIPANTS R and omized intervention trial of 48,835 postmenopausal women in the United States who were of diverse background s and ethnicities and participated in the Women 's Health Initiative Dietary Modification Trial ; 40 % ( 19,541 ) were r and omized to the intervention and 60 % ( 29,294 ) to a control group . Study enrollment was between 1993 and 1998 , and this analysis includes a mean follow-up of 7.5 years ( through August 31 , 2004 ) . INTERVENTIONS The intervention included group and individual sessions to promote a decrease in fat intake and increases in vegetable , fruit , and grain consumption and did not include weight loss or caloric restriction goals . The control group received diet-related education material s. MAIN OUTCOME MEASURE Change in body weight from baseline to follow-up . RESULTS Women in the intervention group lost weight in the first year ( mean of 2.2 kg , P<.001 ) and maintained lower weight than control women during an average 7.5 years of follow-up ( difference , 1.9 kg , P<.001 at 1 year and 0.4 kg , P = .01 at 7.5 years ) . No tendency toward weight gain was observed in intervention group women overall or when stratified by age , ethnicity , or body mass index . Weight loss was greatest among women in either group who decreased their percentage of energy from fat . A similar but lesser trend was observed with increases in vegetable and fruit servings , and a nonsignificant trend toward weight loss occurred with increasing intake of fiber . CONCLUSION A low-fat eating pattern does not result in weight gain  in postmenopausal women . Clinical Trial Registration Clinical Trials.gov , NCT00000611 Dietary glycemic load , the mathematical product of the glycemic index ( GI ) of a food and its carbohydrate content , has been proposed as an indicator of the glucose response and insulin dem and induced by a serving of food . To vali date this concept in vivo , we tested the hypotheses that 1 ) . portions of different foods with the same glycemic load produce similar glycemic responses ; and 2 ) . stepwise increases in glycemic load for a range of foods produce proportional increases in glycemia and insulinemia . In the first study , 10 healthy subjects consumed 10 different foods in r and om order in amounts calculated to have the same glycemic load as one slice of white bread . Capillary blood sample s  were taken at regular intervals over the next 2 h. The glycemic response as determined by area under the curve was not different from that of white bread for nine foods . However , lentils produced lower than predicted responses ( P < 0.05 ) . In the second study , another group of subjects was tested to determine the effects of increasing glycemic load using a balanced 5 x 5 Greco-Latin square design balanced for four variables : subject , dose , food and order . Two sets of five foods were consumed at five different glycemic loads ( doses ) equivalent to one , two , three , four and six slices of bread . Stepwise increases in glycemic load produced significant and predictable increases in both glycemia ( P < 0.001 ) and insulinemia ( P < 0.001 ) . These findings support the concept of dietary glycemic load as a measure of overall glycemic response and insulin dem and BACKGROUND The role of glycemic index ( GI ) in appetite and body-weight regulation is still not clear . OBJECTIVE The objective of the study was to investigate the long-term effects of a low-fat , high-carbohydrate diet with either low glycemic index ( LGI ) or high glycemic index ( HGI ) on ad libitum energy intake , body weight , and composition , as well as on risk factors for type 2 diabetes and ischemic heart disease in overweight healthy subjects . DESIGN The study was a 10-wk parallel , r and omized , intervention trial with 2 matched groups . The LGI or HGI test foods , given as replacements for the subjects ' usual carbohydrate-rich foods , were equal in total energy , energy density , dietary fiber , and macronutrient composition . Subjects were 45 ( LGI diet : n = 23 ; HGI diet : n = 22 ) healthy overweight [ body mass index ( in kg/m(2 ) ) : 27.6 + /- 0.2 ] women aged 20 - 40 y. RESULTS Energy intake , mean ( + /- SEM ) body weight ( LGI diet : -1.9 + /- 0.5 kg ; HGI diet : -1.3 + /- 0.3 kg ) , and fat mass ( LGI diet : -1.0 + /- 0.4 kg ; HGI diet : -0.4 + /- 0.3 kg ) decreased over time , but the differences between groups were not significant . No significant differences were observed between groups in fasting serum insulin , homeostasis model assessment for relative insulin resistance , homeostasis model assessment for beta cell function , triacylglycerol , nonesterified fatty acids , or HDL cholesterol . However , a 10 % decrease in LDL cholesterol ( P < 0.05 ) and a tendency to a larger decrease in total cholesterol ( P = 0.06 ) were observed with consumption of the LGI diet as compared with the HGI diet . CONCLUSIONS This study does not support the contention that low-fat LGI diets are more beneficial than HGI diets with regard to appetite or body-weight regulation as evaluated over 10 wk . However , it confirms previous findings of a beneficial effect of LGI diets on risk factors for ischemic heart disease The National Weight Control Registry ( NWCR ) is , to the best of our knowledge , the largest study of individuals successful at long-term maintenance of weight loss . Despite extensive histories of overweight , the 629 women and 155 men in the registry lost an average of 30 kg and maintained a required minimum weight loss of 13.6 kg for 5 y. A little over one-half of the sample lost weight through formal programs ; the remainder lost weight on their own . Both groups reported having used both diet and exercise to lose weight and nearly 77 % of the sample reported that a triggering event had preceded their successful weight loss . Mean ( + /-SD ) current consumption reported by registry members was 5778 + /- 2200 kJ/d , with 24 + /- 9 % of energy from fat , Members also appear to be highly active : they reported expending approximately 11830 kJ/wk through physical activity . Surprisingly , 42 % of the sample reported that maintaining their weight loss was less difficult than losing weight . Nearly all registry members indicated that weight loss led to improvements in their level of energy , physical mobility , general mood , self-confidence , and physical health . In summary , the NWCR identified a large sample of individuals who were highly successful at maintaining weight loss . Future prospect i ve studies will determine variables that predict continued maintenance of weight loss BACKGROUND The optimal nutritional approach for the prevention of cardiovascular disease among obese persons remains a topic of intense controversy . Available approaches range from conventional low-fat to very-low-carbohydrate diets . OBJECTIVE The aim of this pilot study was to evaluate the efficacy of an ad libitum low-glycemic load diet , without strict limitation on carbohydrate intake , as an alternative to a conventional low-fat diet . DESIGN A r and omized controlled trial compared 2 dietary treatments in obese young adults ( n = 23 ) over 12 mo . The experimental treatment emphasized ad libitum consumption of low-glycemic-index foods , with 45 - 50 % of energy from carbohydrates and 30 - 35 % from fat . The conventional treatment was restricted in energy ( 250 - 500 kcal/d deficit ) and fat ( < 30 % of energy ) , with 55 - 60 % of energy from carbohydrate . We compared changes in study outcomes by repeated- measures analysis of log-transformed data and expressed the results as mean percentage change . RESULTS Body weight decreased significantly over a 6-mo intensive intervention in both the experimental and conventional diet groups ( -8.4 % and -7.8 % , respectively ) and remained below baseline at 12 mo ( -7.8 % and -6.1 % , respectively ) . The experimental diet group showed a significantly greater mean decline in plasma triacylglycerols than did the conventional diet group ( -37.2 % and -19.1 % , respectively ; P = 0.005 ) . Mean plasminogen activator inhibitor 1 concentrations decreased ( -39.0 % ) in the experimental diet group but increased ( 33.1 % ) in the conventional diet group ( P = 0.004 ) . Changes in cholesterol concentrations , blood pressure , and insulin sensitivity did not differ significantly between the groups . CONCLUSION An ad libitum low-glycemic load diet may be more efficacious than a conventional , energy-restricted , low-fat diet in reducing cardiovascular disease risk The effects of macronutrient composition on fasting and postpr and ial activities of adipose tissue lipoprotein lipase ( ATLPL ) and skeletal muscle LPL ( SMLPL ) and on insulin sensitivity ( S(I ) ) were studied in 25 normal-weight subjects . Each subject was fed a high-carbohydrate ( HC ) diet for 16 d and a high-fat ( HF ) diet for 16 d , in r and omized order . On day 15 of each diet , biopsies for ATLPL and SMLPL were done in the fasted state and 6 h postpr and ially . On day 16 of each diet , a euglycemic clamp was used to measure S(I ) . There was no effect of diet composition on fasting ATLPL or SMLPL . With both diets and in both tissues , LPL increased significantly from fasting to 6 h postpr and ially . In adipose tissue only there was a significant difference between the 2 diets in LPL meal response ( HC > HF , P = 0.024 ) . There was no effect of diet composition on S(I ) . After the HC diet only , there were significant correlations between fasting SMLPL and S(I ) , but not ATLPL . After the HF diet , associations between insulin action and LPL were evident only in the postpr and ial state . In summary , 16 d of HC compared with HF feeding in normal-weight subjects increased the responsiveness of ATLPL to an HC compared with an HF meal . However , the same diets had no effect on fasting ATLPL or SMLPL , the responsiveness of SMLPL to a meal , or S(I ) . These data suggest that in normal-weight subjects habitual dietary carbohydrate intake may have a stronger effect on subcutaneous fat storage than does dietary fat intake OB 
    Output:
    
In a systematic review to estimate the optimal dietary fat to carbohydrate ratio , it was found that obese subjects with hyperinsulinemia ( or insulin resistance ) lost more weight on a mild low-carbohydrate ( LC ) ( or low-glycemic load diet ; 40 % carbohydrate , 30 - 35 % fat ) than on a low-fat ( LF ) diet ( 55 - 60 % carbohydrate , 20 % fat ) , whereas those without hyperinsulinemia showed the opposite .
In non-obese primarily insulin-sensitive subjects , decreasing  fat rather than carbohydrate intake is generally more effective to prevent obesity .
Physiological and molecular evidence supports this conclusion .
Increased carbohydrate intake , especially in high-glycemic food , leads to postpr and ial hyperglycemia and hyperinsulinemia , which are exaggerated in obese insulin-resistant subjects .
Even in an insulin-resistant state , insulin is able to stimulate fatty acid synthesis in liver , activate lipoprotein lipase , and prevent lipolysis in adipose tissues , which all facilitate adipose tissue enlargement .