***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 Underreporting of food intake is common in obese subjects . OBJECTIVE One aim of this study was to assess to what extent underreporting by obese men is explained by underrecording ( failure to record in a food diary everything that is consumed ) or undereating . Another aim of the study was to find out whether there was an indication for selective underreporting . DESIGN Subjects were 30 obese men with a mean ( + /-SD ) body mass index ( in kg/m(2 ) ) of 34 + /- 4 .  Total food intake was measured over 1 wk . Energy expenditure ( EE ) was measured with the doubly labeled water method , and water loss was estimated with deuterium-labeled water .  Energy balance was checked for by measuring body weight at the start and end of the food-recording week and 1 wk after the recording week . RESULTS Mean energy intake and EE were 10.4 + /- 2.5 and 16.7 + /- 2 . 4 MJ/d , respectively ; underreporting was 37 + /- 16 % . The mean body mass loss of 1.0 + /- 1.3 kg over the recording week was significantly different ( P < 0.05 ) from the change in body mass over the nonrecording week , and indicated 26 % undereating . Water intake ( reported + metabolic water ) and water loss were significantly different from each other and indicated 12 % underrecording . The reported percentage of energy from fat was a function of the level of underreporting : percentage of energy from fat = 46 - 0.2 x percentage of underreporting ( r(2 ) = 0.28 , P = 0.003 ) . CONCLUSIONS Total underreporting by the obese men was explained by underrecording and undereating . The obese men selectively underreported fat intake Kay-Tee Khaw and colleagues analyze data from a prospect i ve cohort study  and show associations between plasma concentrations of saturated phospholipid fatty acids and risk of coronary heart disease , and an inverse association between omega-6 polyunsaturated phospholipid fatty acids and risk of coronary heart disease OBJECTIVE To evaluate the validity of the Northern Sweden eighty-four-item FFQ to estimate intake of fatty acids  relative to 24 h diet recalls ( 24-HDR ) and fatty acids in erythrocyte membranes . DESIGN Participants , r and omly recruited from the population -based Västerbotten Intervention Project , answered the eighty-four-item FFQ . During the following year each participant carried out ten 24-HDR . Intake of fatty acids measured by the FFQ was compared with intake by the 24-HDR and fatty acid levels in erythrocytes . SETTING The county of Västerbotten in northern Sweden . SUBJECTS Ninety-six men and ninety-nine women . RESULTS Spearman correlation coefficients ( rs ) between intakes of the fatty acids 14 : 0 , 15 : 0 , 16 : 0 , 17 : 0 , 18 : 2n-6 , 18 : 3n-3 , 20 : 5n-3 and 22 : 6n-3 estimated by the FFQ and the 24-HDR were all significant and ranged from 0.29 ( 22 : 6n-3 in men and women ) to 0.60 ( 16 : 0 in men ) , whereas significant correlations between FFQ-estimated intake and erythrocyte membrane content were only seen for milk fatty acids 14 : 0 , 15 : 0 and 17 : 0 ( rs = 0.23 - 0.34 ) and fish fatty acids 20 : 5n-3 and 22 : 6n-3 ( rs = 0.42 - 0.51 ) . CONCLUSION The Northern Sweden eighty-four-item FFQ gives a satisfactory estimate of the intake of fish fatty acids ( 20 : 5n-3 and 22 : 6n-3 ) and milk fatty acids ( 15 : 0 and 17 : 0 ) , whereas its validity for fatty acids 18 : 2n-6 and 18 : 3n-3 , derived mainly from vegetable oils , can not be shown BACKGROUND Self-report of dietary intake could be biased by social desirability or social approval thus affecting risk estimates in epidemiological studies . These constructs produce response set biases , which are evident when testing in domains characterized by easily recognizable correct or desirable responses . Given the social and psychological value ascribed to diet , assessment method ologies used most commonly in epidemiological studies are particularly vulnerable to these biases . METHODS Social desirability and  social approval biases were tested by comparing nutrient scores derived from multiple 24-hour diet recalls ( 24HR ) on seven r and omly assigned days with those from two 7-day diet recalls ( 7DDR ) ( similar in some respects to commonly used food frequency question naires ) , one administered at the beginning of the test period ( pre ) and one at the end ( post ) . Statistical analysis included correlation and multiple linear regression . RESULTS Cross-sectionally , no relationships between social approval score and the nutritional variables existed . Social desirability score was negatively correlated with most nutritional variables . In linear regression analysis , social desirability score produced a large downward bias in nutrient estimation in the 7DDR relative to the 24HR . For total energy , this bias equalled about 50 kcal/point on the social desirability scale or about 450 kcal over its interquartile range . The bias was approximately twice as large for women as for men and only about half as large in the post measures . Individuals having the highest 24HR-derived fat and total energy intake scores had the largest downward bias due to social desirability . CONCLUSIONS We observed a large downward bias in reporting food intake related to social desirability score . These results are consistent with the theoretical constructs on which the hypothesis is based . The effect of social desirability bias is discussed in terms of its influence on epidemiological estimates of effect . Suggestions are made for future work aim ed at improving dietary assessment method ologies and adjusting risk estimates for this bias The authors assessed the reproducibility and validity of an exp and ed 131-item semiquantitative food frequency question naire used in a prospect i ve study among 51,529 men . The form was administered by mail twice to a sample of 127 participants at a one-year interval . During this interval , men completed two one-week diet records spaced approximately 6 months apart . Mean values for intake of most nutrients assessed by the two methods were similar . Intraclass correlation coefficients for nutrient intakes assessed by question naires one year apart ranged from 0.47 for vitamin E without supplements to 0.80 for vitamin C with supplements .  Correlation coefficients between the energy-adjusted nutrient intakes measured by diet records and the second question naire ( which asked about diet during the year encompassing the diet records ) ranged from 0.28 for iron without supplements to 0.86 for vitamin C with supplements ( mean r = 0.59 ) . These correlations were higher after adjusting for week-to-week variation in diet record intakes ( mean r = 0.65 ) . These data indicate that the exp and ed semiquantitative food frequency question naire is reproducible and provides a useful measure of intake for many nutrients over a one-year period 
    Output:
    
We found some evidence that circulating levels of eicosapentaenoic and docosahexaenoic acid ( the 2 main types of long-chain -3 fatty acids ) and arachidonic acid were each associated with lower coronary risk .