***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 Mastication is the first step in ingesting food , but the effects of mastication on energy intake and gut hormones in both obese and lean subjects have not been extensively evaluated . OBJECTIVE The current study aim ed to compare the differences in chewing activities between obese and lean subjects and to examine the effects of chewing on energy intake and gut hormone concentrations in both obese and lean subjects . DESIGN Sixteen lean and 14 obese young men participated in the current research . In study 1 , we investigated whether the chewing factors of obese subjects were different from those of lean subjects . In study 2 , we explored the effects of chewing on energy intake . A test meal consisting of 2200 kJ ( 68 % of energy as carbohydrate , 21 % of energy as fat , and 11 % of energy as protein ) was then consumed on 2 different sessions ( 15 chews and 40 chews per bite of 10 g of food ) by each subject to assess the effects of chewing on plasma gut hormone concentrations . RESULTS Compared with lean participants , obese participants had a higher ingestion rate and a lower number of chews per 1 g of food . However , obese participants had a bite size similar to that of lean subjects . Regardless of status , the subjects ingested 11.9 % less after 40 chews than after 15 chews . Compared with 15 chews , 40 chews result ed in lower energy intake and postpr and ial ghrelin concentration and higher postpr and ial glucagon-like peptide 1 and cholecystokinin concentrations in both lean and obese subjects . CONCLUSION Interventions aim ed at improving chewing activity could become a useful tool for combating obesity . This trial was registered at chictr.org as ChiCTR-OCC-10001181 BACKGROUND Epidemiologic and clinical data indicate that nuts can be incorporated into the diet without compromising body weight . This has been attributed to strong satiety properties , increased resting energy expenditure , and limited lipid bioaccessibility . OBJECTIVE The role of mastication was explored because of evidence that the availability of nut lipids is largely dependent on the mechanical fracture of their cell walls . DESIGN In a r and omized , 3-arm , crossover study , 13 healthy adults ( body mass index , in kg/m(2 ) : 23.1 + /- 0.4 )  chewed 55 g almonds 10 , 25 , or 40 times .  Blood was collected and appetite was monitored during the following 3 h. Over the next 4 d , all foods were provided , including 55 g almonds , which were consumed under the same chewing conditions . Complete fecal sample s were collected . RESULTS Hunger was acutely suppressed below baseline ( P < 0.05 ) , and fullness was elevated above baseline longer ( P < 0.05 ) after 40 chews than after 25 chews . Two hours after consumption , fullness levels were significantly lower and hunger levels were significantly higher after 25 chews than after 10 and 40 chews ( P < 0.05 ) . Initial postingestive glucagon-like peptide-1 concentrations were significantly lower after 25 chews than after 40 chews ( P < 0.05 ) , and insulin concentrations declined more rapidly after 25 and 40 chews than after 10 chews ( both P < 0.05 ) . Fecal fat excretion was significantly higher after 10 chews than after 25 and 40 chews ( both P < 0.05 ) . All participants had higher fecal energy losses after 10 and 25 chews than after 40 chews ( P < 0.005 ) . CONCLUSION The results indicate important differences in appetitive and physiologic responses to masticating nuts and likely other foods and nutrients . This trial was registered at clinical trials.gov as NCT00768417 Prolonged chewing of food can reduce meal intake . However , whether prolonged chewing influences intake at a subsequent eating occasion is unknown . We hypothesised that chewing each mouthful for 30s would reduce afternoon snack intake more than ( a ) an habitual chewing control condition , and ( b ) an habitual chewing condition with a pauses in between each mouthful to equate the meal duration s. We further hypothesised that this effect may be related to effects of prolonged chewing on lunch memory . Forty three participants ate a fixed lunch of s and wiches in the laboratory . They were r and omly allocated to one of the three experimental groups according to a between-subjects design . Appetite , mood and lunch enjoyment ratings were taken before and after lunch and before snacking . Snack intake of c and ies at a taste test 2h after lunch was measured as well as rated vividness of lunch memory . Participants in the prolonged chewing group ate significantly fewer c and ies than participants in the habitual chewing group . Snack intake by the pauses group did not differ from either the prolonged or habitual chewing groups . Participants in the prolonged chewing group were less happy and enjoyed their lunch significantly less than participants in other conditions . Appetite ratings were not different across groups . Rated vividness of lunch memory was negatively correlated with intake but there was no correlation with rated lunch enjoyment . Prolonged chewing of a meal can reduce later snack intake and further investigation of this technique for appetite control is warranted To determine the influence of masticatory efficiency on postpr and ial satiety and glycaemic response , twenty-one healthy males were recruited for this r and omised cross-over trial . The participants consumed a fixed amount of pizza provided in equal-sized portions by chewing each portion either fifteen or forty times before swallowing .  Subjective appetite was measured by appetite question naires at regular intervals for 3 h after the meal and plasma sample s were collected for the measurement of selected satiety-related hormones , glucose , insulin and glucose-dependent insulinotropic peptide ( GIP ) concentrations . An ad libitum meal was provided shortly after the last blood sample was drawn and the amount eaten recorded . Compared with fifteen chews , chewing forty times per portion result ed in lower hunger ( P= 0·009 ) , preoccupation with food ( P= 0·005 ) and desire to eat ( P= 0·002 ) . Meanwhile , plasma concentrations of glucose ( P= 0·024 ) , insulin ( P < 0·001 ) and GIP ( P < 0·001 ) were higher following the forty-chews meal . Chewing forty times before swallowing also result ed in a higher plasma cholecystokinin concentration ( P= 0·045 ) and a trend towards a lower ghrelin concentration ( P= 0·051 ) . However , food intake at the subsequent test meal did not differ ( P= 0·851 ) . The results suggest that a higher number of masticatory cycles before swallowing may provide beneficial effects on satiety and facilitate glucose absorption Chewing reportedly contributes to satiation and satiety signals . Attempts to document and quantify this have led to small and inconsistent effects . The present trial manipulated oral processing effort though required chewing of gums of different hardness and measured appetitive sensations , energy intake , gastric emptying , GI transit time , and concentrations of glucose , insulin , GLP-1 , ghrelin and pancreatic polypeptide . Sixty adults classified by sex and BMI ( 15 each of lean females , obese females , lean males and obese males ) were tested in a r and omized , controlled , cross-over trial with three arms . They chewed nothing , soft gum or hard gum for 15 min while sipping grape juice ( 10 % of individual energy needs ) containing acetaminophen and lactulose on one day each separated by 7 days . Electromyographic recordings and self-reports were obtained during and after chewing to quantify oral processing effort . Blood was sample d through an indwelling catheter and appetite ratings were obtained at baseline and at 0 , 15 , 30 , 45 , 60 , 90 , 120 , 180 and 240 min after chewing initiation . Breath sample s were collected at 10 min intervals for the first 2h and at 30 min intervals for the next 2h . No effects of chewing were observed for appetitive sensations or gut peptide concentrations . Energy intake tended to decline in lean and increase in obese participants so that daily energy intake differed significantly between the two groups when chewing either gum , while no difference was observed on the non-chewing day . Serum glucose and insulin were significantly lower at selected time points 90 - 240 min after chewing compared to baseline and the non-chewing day . These data indicate chewing effort does not affect appetitive sensations or gut peptide secretion , but may exert a small differential effect on acute energy intake in lean and obese individuals and lead to greater post-pr and ial declines of serum glucose and insulin . The efficacy of gum chewing as a substitute for eating for weight management remains uncertain UNLABELLED Ghrelin has been suggested to function as an appetite-stimulating signal from the gastrointestinal tract to the brain acting through a vagal afferent pathway . Ghrelin levels rise before meals and fall after meal ingestion . The purpose of this study was to investigate factors which regulate ghrelin release into the circulation by determining changes in systemic ghrelin concentrations after sham feeding and meal ingestion . METHODS Fifteen normal subjects underwent sham feeding of a bacon and cheese toasted s and wich .  Serial blood sample s were obtained before and every 5 min for another 30 min during sham feeding and for 30 min after actual meal ingestion . Radioimmunoassay was used to measure plasma ghrelin and pancreatic polypeptide concentrations . RESULTS During sham feeding , plasma ghrelin concentration increased from 1730+/-237 to 1917+/-269 pg/mL ( P<0.05 ) and plasma pancreatic polypeptide increased from 417+/-50 to 841+/-97 pg/mL ( P<0.01 ) . Subsequent meal ingestion was characterized by an increase in pancreatic polypeptide from 782+/-88 to 1710+/-119 pg/mL ( P<0.01 ) , but no significant change in ghrelin levels . CONCLUSIONS Plasma ghrelin and pancreatic polypeptide concentrations increase with sham feeding . This suggests a vagal efferent pathway mediating ghrelin release . In contrast to pancreatic polypeptide which rises with actual meal ingestion , ghrelin levels did not change Eating slowly contributes to a lower risk of obesity , probably because it could aid appetite control .  Chewing thoroughly is an effective strategy to reduce eating rate ; however , insufficient data are available to demonstrate the relationship between such an eating behavior and energy intake . To investigate the effect of increasing the number of chews before swallowing on meal size , a r and omized cross-over trial was conducted in 18- to 45-year-old normal-weight , overweight , and obese participants ( n=45 ) who were recruited from the local community ( Ames , IA ) . After assessment of baseline number of chews , participants were asked to attend three test sessions to eat pizza for lunch until comfortably full by chewing each portion of food either 100 % , 150 % , or 200 % of their baseline number of chews before swallowing . Two-way analysis of variance was used to test the effect of treatment and body-weight status , as well as their interactions on food intake , meal duration , eating rate , and appetite at meal termination . Appetite data during 60 minutes were analyzed by repeated measures analysis of variance . Food intake in the sessions with 150 % and 200 % of their baseline number of chews was reduced significantly , by 9.5 % and 14.8 % , respectively , compared with the 100 % session . Increasing the number of chews also prolonged meal duration and reduced eating rate . However , subjective appetite at meal termination or during the immediate postpr and ial period did not differ . These data indicate that increasing the number of chews before swallowing might be a behavioral strategy to reduce food intake and potentially aid body-weight management Appetite is regulated by many factors , including oro-sensory and gastric signals . There are many studies on contributions of and possible interaction between sensory and gastric stimulation , but there are few studies in humans using simultaneous oral and gastric stimulation . We investigated the effect of simultaneous , but independently manipulated , oral and gastric stimulation on appetite ratings and energy intake . We hypothesized that compared with no stimulation , oral and gastric stimulation would equally and additively decrease appetite ratings and energy intake .  Healthy men ( n = 26 , 21 ± 2 years , BMI 22 ± 3 kg/m(2 ) ) participated in a r and omized crossover trial with four experimental conditions and a control condition . Experimental conditions consisted of oral stimulation , with either 1 or 8 min modified sham feeding ( MSF ) , and gastric stimulation , with either 100 or 800 ml intragastrically infused liquid ( isocaloric , 99 kcal , 100 ml/min ) . The control condition consisted of no oral or gastric stimulation . Outcome measures were energy intake 30 min after the treatment and appetite ratings . Compared with the control condition , energy intake decreased significantly after the 8 min/100 ml ( 19 % lower , P = 0.001 ) and 8 min/800 ml 
    Output:
    
Analysis of the heterogeneity found a substantial effect of the fasting period where the duration of fasting influenced the decrease in hunger due to chewing .
Evidence currently suggests that chewing may decrease self-reported hunger and food intake , possibly through alterations in gut hormone responses related to satiety .